Introduction
Irritability has long featured in the clinical descriptions of many psychological disorders, however, it is only in recent years that the construct has been subject to extensive scientific investigation in its own right. Recent interest in the construct has arisen in part from assertions that it represents a key transdiagnostic construct implicated in diverse forms of psychopathology, with developmental origins early in life (Beauchaine & Tackett,
2020; Klein et al.,
2021). Accordingly, disorders of childhood and adolescence have been a key focus of emerging research into irritability, which has spanned topics from measurement and diagnostic models, through to risk mechanisms and intervention targets (e.g., Leibenluft et al.,
2024; Zachary & Jones,
2019). Moreover, there is growing recognition that irritability is one of the most common reasons for referral to mental health services in childhood (Evans et al.,
2023). Irritability nonetheless remains a somewhat elusive construct, and researchers have just begun to synthesize the expansive evidence base that now exists, through systematic approaches such as meta-analysis (Brotman et al.,
2017; Finlay-Jones et al.,
2024; Vidal-Ribas et al.,
2016).
Current definitions of irritability refer primarily to low frustration tolerance (Toohey & DiGiuseppe,
2017) or a low threshold for experiencing anger in response to slight provocation, incongruent with developmental age (Brotman et al.,
2017). In diagnostic models, irritability has often been operationalized as a categorical symptom and conceptualized largely as a state-dependent mood lasting days to weeks, occurring in the absence of an obvious trigger. In literature on individual differences concerning temperament and personality, irritability has been conceptualized as the extreme expression of a dimensionally distributed trait that is heritable and relatively stable from early childhood to adulthood (Beauchaine & Tackett,
2020; Leibenluft & Stoddard,
2013).
Researchers have employed a wide range of measurement strategies to capture various aspects of irritability in child and adolescent samples, such as indexing mood versus behavior or persistent irritability versus temper outbursts. Common approaches have included the selection of specific symptom items from diagnostic interviews (e.g., Kiddie Schedule for Affective Disorders and Schizophrenia; Kaufman et al.,
2000), subscales from temperament questionnaires (e.g., Child Behavior Questionnaire; Rothbart et al.,
2001), along with instruments specifically designed to index irritability (e.g., Affective Reactivity Index; Stringaris et al.,
2012). Research suggests that the prevalence and severity of irritability may significantly differ depending on whether the measure is self-report, parent-report, or teacher report (De Los Reyes et al.,
2015; Evans et al.,
2023). Moreover, from a developmental perspective, the age at which irritability is indexed can have important implications for conceptualization and measurement. There is support for the measurement of irritability as a distinct temperament dimension from infancy (Rothbart,
2011), however, studies of infants and toddlers have often operationalized irritability using non-specific indices (e.g., excessive crying) or broader dimensions such as negative emotionality that encompass other forms of distress (Finlay-Jones et al.,
2024). As a specific mental health construct, irritability can present at clinically significant levels in children as young as 2 years (Camacho et al.,
2019). Measures of irritability have often been used to operationalize the clinical expression of emotion dysregulation, which itself encompasses processes including emotional expressions and experiences that are inappropriate to context or excessive based on social norms; shifts in emotion that are rapid or poorly controlled; and the atypical allocation of attention to emotional stimuli (Evans et al.,
2021a; Vogel et al.,
2019; Shaw et al.,
2014).
Evidence regarding irritability has important implications for the diagnosis and classification of child and adolescent psychopathology. The
Diagnostic and Statistical Manual of Mental Disorders (DSM-5) (American Psychiatric Association; APA,
2013) and
The International Classification of Disease (ICD-11) (World Health Organization,
2022) both include irritability as a symptom in the criteria for disorders including oppositional defiant disorder (ODD), major depressive disorder in children and adolescents, and generalized anxiety disorder. ODD, for example, includes a distinct symptom dimension reflecting chronic irritability, which is thought to account in part for findings that ODD in childhood is a common precursor to many other forms of psychopathology across adolescence and later life (e.g., depression, suicidality, substance use, psychosis) (Burke et al.,
2021; Hawes et al.,
2023). Recent revisions to the major diagnostic systems also reflect ongoing debate regarding the classification of chronic irritability (Evans et al.,
2021a; Fristad,
2021; Runions et al.,
2016). For example, DSM-5 included a new childhood mood disorder, Disruptive Mood Dysregulation Disorder (DMDD), whereas ICD-11 introduced chronic irritability as a specifier within ODD (See also: Copeland et al.,
2013; Lochman et al.,
2015).
Interest in irritability as a transdiagnostic construct has grown significantly in recent years, driving considerable research into associations between irritability and various symptom domains. In addition to testing these associations through methods such as factor analysis and network analysis (e.g., Burke et al.,
2014; Tseng et al.,
2023), meta-analysis has been used in two studies to date. Vidal-Ribas et al. (
2016) analyzed data from 12 longitudinal studies of chronic non-episodic irritability as a predictor of future mental health disorders. Irritability was reported to be significantly associated with depression and anxiety but not conduct problems such as ODD and conduct disorder (CD), and research priorities were identified, including the need for studies using high-quality measures of irritability. Research in the area has since grown rapidly, and a number of such measures have been widely adopted, including the Affective Reactivity Index, which is recommended in DSM-5 as a cross cutting symptom measure for irritability in 6–17-year-olds (APA,
2013).
A more recent meta-analysis of 98 longitudinal studies focused specifically on indices of irritability prior to 5 years of age, as predictors of later disorders across childhood and adolescence. Results indicated a small but significant association between infant (0–12 months) and preschool/toddler (13–60 months) irritability and later internalizing and externalizing disorders (Finlay-Jones et al.,
2024). The meta-analytic findings of Finlay-Jones et al. (
2024) support early irritability during ages 0–5 years as a transdiagnostic neurodevelopmental vulnerability to later psychopathology. At the same time, there exists an extensive and largely separate body of research in which irritability and broader symptoms of psychopathology have been indexed across childhood and adolescence. It is this evidence base that is the focus of our review.
Results
Characteristics of Included Studies
Overall, data from 119 studies were analyzed, with 541 effect sizes. There were 77 studies reporting concurrent associations between irritability and mental health symptoms, with 417 effect sizes (n = 66,326). The grand mean age for concurrent associations was 10.6 (± 3.0) years. There were 42 studies reporting longitudinal associations, with 124 effect sizes (n = 56,130). Longitudinal model 2 (preschool to childhood; n = 13,964), included 15 studies representing 65 effect sizes. The grand mean age was 3.9 (± 1.2) years at baseline and 9.2 (± 3.1) years at follow-up. Longitudinal model 3 (childhood to later childhood/adolescence; n = 36,201) included 20 studies representing 39 effect sizes. The grand mean age was 8.1 (± 2.6) years at baseline and 12.4 (± 2.7) years at follow-up. Longitudinal model 4 (childhood to adulthood) included only one study, and therefore could not be conducted (the data from this study were included in model 6). Longitudinal model 5 (adolescence to adolescence; n = 3851) included 4 studies representing 11 effect sizes. The grand mean age was 14.5 (± 0.5) years at baseline and 16.5 (± 1.3) years at follow-up. Longitudinal model 6 (adolescence to adulthood; n = 1840) included 4 studies representing 9 effect sizes. The grand mean age was 14.4 (± 2.8) years at baseline and 22.1 (± 4.0) years at follow-up.
There was a total of 122,456 participants, including 57,593 females (47.0%) and 64,872 males (53.0%), with 4674 sex unknown (3.8%). The samples were from North and South America (
n = 74), Europe (
n = 28), Australia (
n = 7), Asia (
n = 7), and multicontinental (
n = 3). There were 36 measures of irritability in the form of parent, self, and teacher reports. The mean score for study quality was 16.8 (± 1.5; range = 12–20), suggesting high reporting standards (Table S2). Characteristics of the included studies are displayed in Table
1.
Table 1
Characteristics of included studies
Aebi et al. (2016) | 158 | Cross-sectional | Switzerland | Boys | 16.89 (1.13) | – | – | Self: MINI-KID | Affective disorders Anxiety disorders Conduct disorder ADHD Suicidality | 18 | 1 |
Aebi et al. (2013) | 1031 | Cross-sectional | Switzerland | Both (50%) | 13.85 (1.63) | 29.6 (1.63) | – | Self: CBCL-YSR Parent: CBCL | Anxious/depressed Attention problems Delinquent behavior Depression Any crime | 18 | 1 |
Ali et al. (2022) | T1:409 T2: 394 T3: 365 | Longitudinal | England | Both (49%) | 3.43 (0.30) | 5.93 | 8.59 | Observation: LAB-TAB Irritability | Internalizing Externalizing Depression ODD ADHD Conduct disorder | 16 | 2 |
Althoff et al. (2014) | S1: 2029 S2: 2076 S3: 399 Total: 4504 | Cross-sectional | America Dutch | S1: Both (53%) S2: Both (49%) S3: Both (53%) | S1: 6–18 S2: 4–16 S3: 10.88 (3.06) | – | – | Parent: CBCL | ODD Conduct disorder Anxiety ADHD | 15 | 1 |
Ambrosini et al. (2013) | 500 | Cross-sectional | America | Both (73%) | 6–18 | – | – | Self: K-SADS-P | Major depressive disorder ODD MDDD ADHD (combined) ADHD (inattentive) | 15 | 1 |
Arana et al. (2021) | S1: 220 S2: 252 Total: 472 | Cross-sectional | Netherlands | S1: Both (55%) S2: Both (50%) | S1: 11.54 (0.49) S2: 10.85 (0.57) | – | – | Parent: HiPIC – Neg. affectivity subscale | Internalizing Externalizing Attention problems Anxiety | 17 | 1 |
Barclay et al. (2022) | T1: 231 T3: 192 | Longitudinal | America | Both (68%) | 7.4 (1.1) | 9.72 (1.32) | 12.09 (1.36) | Teacher: DBD Parent: DBD | Internalizing Externalizing | 16 | 3 |
Barker & Salekin (2012) | 5923 | Longitudinal | America | Both (51%) | 8 | 10 | – | Parent: DAWBA | Internalizing CU traits Conduct problems Emotional difficulties Callous attitude Peer victimization | 15 | 3 |
Baweja et al. (2021) | 226 | Cross-sectional | America | Both (73%) | 7.6 (1.96) | – | – | Parent: DBDRS | Inattention Hyperactive-Impulsivity Inattentive-overactive-impulsivity Oppositional-defiant Emotional lability | 17 | 1 |
Bell et al. (2023) | 491 | Cross-sectional | Australia | Boys | 12–17 | | | Self: BiTe | Conduct Problems | 18 | 1 |
Benarous et al. (2020a) | 30 | Cross-sectional | Canada | Both (87%) | 6–16 | – | – | Parent: K-SADS-PL | Externalizing Internalizing Depression | 15 | 1 |
Benarous et al. (2020b) | 163 | Cross-sectional | Canada | Both (61%) | 7–17 | – | – | Parent: K-SADS-PL | Anxiety disorders Substance use disorder | 17 | 1 |
Bielas et al. (2016) | 130 | Cross-sectional | Switzerland | Boys | 13–18 | – | – | Self: CIS | Adverse child experience ADHD DBD SUD Suicidality Depressive disorders Anxiety disorders PTSD | 16 | 1 |
Bolhuis et al. (2017) | T1: 6209 T2: 4724 | Longitudinal | Netherlands | Both (50%) | 6 | 10 | – | Parent: CBCL | Physical aggression Oppositional behavior Disobedient behavior Rule-breaking behavior Callous traits | 17 | 3 |
Brandes et al. (2019) | 695 | Cross-sectional | America | Both (48%) | 7–13 | – | – | Parent: CBCL | Internalizing symptoms Externalizing symptoms | 16 | 1 |
Burke (2012) | T1:177 T2: 162 | Longitudinal | America | Boys | 7–12 | 17 | – | Parent: DISC Parent: CSI-IV Parent: DAWBA | Depression Anxiety Conduct disorder ADHD symptoms | 15 | 3 |
| S1: 1517 S2: 2451 S3: 7420 Total: 11,388 | Cross-sectional Cross-sectional Cross-sectional | America America UK | Boys Girls Both (50%) | 7 5–8 10–11 | – | – | Parent: DISC Parent: CSI-IV Parent: DAWBA | Oppositional behavior | 15 | 1 |
Busch et al. (2023) | 194 | Cross-sectional | Germany | Both (60%) | 12.52 (2.69) | – | – | Self: BiTe | Anxiety Depression | 17 | 1 |
Caprara et al. (2017) | 109 | Cross-sectional | Italy | Both (74%) | 11–18 | – | – | Parent: CIS | Aggression Emotional instability Hostile rumination Moral disengagement Agreeableness | 17 | 1 |
Cardinale et al. (2021) | 489 | Cross-sectional | America | Both (55%) | 12.03 (2.41) | – | – | Parent: ARI | ADHD Inattentive ADHD (Hyp/Imp) | 17 | 1 |
Cardinale et al. (2019) | 331 | Cross-sectional | America | Both (46%) | 13.57 (2.69) | – | – | Parent: ARI Self: ARI | ADHD Anxiety DMDD | 17 | 1 |
Carter-Leno et al. (2021) | 52 | Cross-sectional | England | Both (60%) | 13–17 | – | – | Parent: ARI | Autism | 17 | 1 |
Chad-Friedman et al. (2023) | 605 | Longitudinal | America | Both (54%) | 3.52 | 9.23 | 15.25 (.40) | Parent: CBCL | Depression Anxiety Defiance ADHD | 17 | 2 |
Chad-Friedman et al. (2022) | 605 | Longitudinal | America | Both (48%) | 4.17 | 6.07 | – | Parent: Daily diary of mood & affect | Depressive symptoms Anxiety symptoms ADHD symptoms ODD symptoms Global impairment | 20 | 2 |
Chen et al. (2021) | 131 | Cross-sectional | America | Both (40%) | 13 (2.79) | – | – | Self: ARI | Anxiety symptoms Bullying perpetration Peer victimization | 17 | 1 |
Copeland et al. (2015) | 1420 | Cross-sectional | America | Both (50%) | 9–16 | – | – | Parent & Self: CAPA | Depression Anxiety Any impairment | 15 | 1 |
Courbet et al. (2021) | 170 | Cross-sectional | France | Both (76%) | 6–11 | – | – | Parent: ARI | ADHD | 19 | 1 |
Craig et al. (2021) | 179 | Longitudinal | Canada | Both (54%) | 15.34 (1.53) | 18 | – | Self: OCHS | Attachment anxiety Attachment avoidance ODD symptoms Affect dysregulation | 19 | 6 |
DeGroot et al. (2024) | 2548 | Cross-sectional | America | Both (69%) | 12.21 (3.3) | – | – | Parent: CBCL Teacher: CASI | Depressive disorder Anxiety disorder ADHD (combined) ADHD (inattentive) ODD/CD Suicidality | 17 | 1 |
Déry et al. (2017) | 276 | Longitudinal | Canada | Both (60%) | 8.5 (0.9) | 9–12 | – | Parent: DISC | Depression Anxiety ADHD ODD (vindictive) ODD (defiant) | 18 | 3 |
Doerfler et al. (2020) | 310 | Cross-sectional | America | Both (35%) | 10.65 (3.4) | – | – | Parent: K-SADS-P | Depression Anxious/depressed Internalizing symptoms Aggressive behavior Externalizing symptoms Global impairment Total aggression | 17 | 1 |
Dougherty et al. (2015) | 446 | Longitudinal | America | Both (55%) | 3.51 (.26) | 9.25 (.42) | – | Parent: PAPA | Depressive disorder Anxiety Disorder ADHD DBD | 18 | 2 |
Dougherty et al. (2016) | 473 | Longitudinal | America | Both (54%) | 6.10 (0.43) | 9.21 (0.38) | – | Parent: PAPA | Depressive disorder Anxiety Disorder ADHD DBD | 18 | 3 |
Dougherty et al. (2013) | 462 | Longitudinal | America | Both (54%) | 3.6 (0.3) | 6.1 (0.4) | – | Parent: PAPA | Global impairment Depressive disorder Anxiety disorder ADHD ODD | 18 | 2 |
Drabick & Gadow (2012) | S1: 546 S2: 614 Total: 1160 | Cross-sectional | America | S1: Both (73%) S2: Both (67%) | S1:6–11 S2: 12–18 | – | – | Parent: CASI-4R, ASI-4R Teacher: CASI-4R, ASI-4R | ODD ADHD (Inattentive) ADHD (Hyp/Imp): Conduct disorder GAD Social anxiety disorder Major depressive disorder Manic symptoms | 17 | 1 |
Dugre & Potvin (2020) | 4898 | Cross-sectional | Canada | Both (52%) | 5 | – | – | Parent: CBCL | Anxiety Hyperactivity Physical aggression | 17 | 1 |
Elvin et al. (2021) | 93 | Cross-sectional | Australia | Both (56%) | 9.96 (0.36) | – | – | Self: ARI | Self-regulation positive Self-regulation negative Behavioural control Prosocial behavior Peer problems Anxiety Depression Conduct Problems | 17 | 1 |
Elvin et al., (2023) | 84 | Cross-sectional | Australia | Both (45%) | 9.31 (2.44) | – | – | Parent: CBCL | Anxiety | 16 | 1 |
| 237 | Cross-sectional | America | Both (64%) | 9.14 (3.51) | – | – | Parent/youth (6–18): ARI Parent (3–5): ARI | Anxiety Depression Inattention Hyperactivity Suicidality Aggression | 16 | 1 |
Evans et al. (2020a) | 238 | Cross-sectional | America | Both (52%) | 8.9 | – | – | Self: ARI | Anxiety Depressive symptoms Reactive aggression Oppositional behavior | 17 | 1 |
Evans et al. (2020b) | 1030 | Cross-sectional | America | Both (58%) | 10.2 (2.4) | – | – | Parent: CBCL Youth: CBCL-YSR | Internalizing Problems Externalizing Problems Anxious/Depressed Withdrawn/Depressed Somatic Complaints Social Problems Thought Problems Attention Problems Rule-Breaking DSM Affective Problems DSM Anxiety Problems DSM Somatic Problems DSM ADHD Problems DSM Conduct Problems | 18 | 1 |
Evans et al. (2020c) | 346 | Longitudinal | America | Both (49%) | 5–8 | 8–11 | – | Teacher: DBDC Youth DBDC | Defiance Hyperactivity Inattention Depression | 18 | 3 |
Evans et al. (2022) | 206 | Cross-sectional | America | Both (52%) | 10.73 (2.40) | – | – | Caregiver: CBCL Youth: CBCL-YSR | Emotional Lability Anger coping Anger Dysregulation Internalizing Externalizing Attention | 17 | 1 |
Evans et al. (2016) | 706 | Cross-sectional | America | Both (51%) | 5–12 | – | – | Teacher: DBD | Defiant Hyperactive-Impulsive Inattentive Proactive Aggression Reactive aggression Relational aggression Physical aggression Depression | 16 | 1 |
Eyre et al. (2019) | 4874 | Longitudinal | England | Both (57%) | 7–9 | 10–16 | – | Parent: DAWBA | Neurodevelopmental difficulties Depression | 18 | 3 |
Eyre et al. (2017) | 696 | Cross-sectional | UK | Both (84%) | 10.9 (2.99) | – | – | Parent: CAPA | Anxiety Depression | 17 | 1 |
Ezpeleta et al. (2012) | 622 | Cross-sectional | Spain | Both (51%) | 3.0 (0.18) | – | – | Parent: DICA-PPYC | Disruptive ADHD Mood disorders Minor depression Anxiety disorders SAD Specific phobia Social phobia | 17 | 1 |
Ezpeleta et al. (2019) | 614 | Cross-sectional | Spain | Both (50.2%) | 3.8(0.33) | 7 | – | Parent: SDQ | Affective problems Anxiety problems ODD problems | 19 | 1 |
Ezpeleta et al. (2020a) | T1: 471 T2: 454 | Longitudinal | Spain | T1: Both (49%) T2: Both (49%) | 7.7 (0.36) | 11.6 (0.34) | – | Teacher: ARI | Anger SDQ-Conduct SDQ-Emotional SDQ-Hyperactivity SDQ-Peer SDQ-Prosocial SDQ-Externalizing (Conduct + Hyper) SDQ-Internalizing (Emotional + Peer) CAS-Verbal Aggression CAS-Aggression against objects/animals CAS-Physical aggression CAS-Use of weapons CAS-Aggression to peers CAS Total CBCL-Withdrawn/Depressed CBCL-Anxious/Depressed CBCL-Attention problems CBCL-Aggressive behavior CBCL-Rule-Breaking ERC-Lability-Negativity ERC-Emotion regulation YSR-Withdrawn/Depressed YSR-Anxious/depressed YSR-Attention problems YSR-Aggressive behavior YSR-Rule-Breaking AQ-Tolerance to frustration AQ-External expression AQ-Anger control | 19 | 3 |
Ezpeleta et al. (2020b) | Cl1: 332 Cl2: 55 CI3: 108 Total: 495 | Longitudinal | Spain | Cl1: Both (52%) Cl2: Both (53%) Cl3: Both (47%) | 3 | 11–12 | – | Parent: SDQ | ASR-Anxious/depressed ASR-withdrawn ASR-somatic complaints ASR-thought problems ASR-Attention problems ASR-Aggressive behavior ASR-rule-breaking ASR-Intrusive ASR-internalizing ASR-externalizing SDQ-emotion SDQ-conduct SDQ- hyperactivity SDQ-peer SDQ-prosocial Functional impairment | 18 | 2 |
Ezpeleta et al. (2022) | 563 | Cross-sectional | Spain | Both (51%) | 6–13 | – | – | Parent: SDQ | Trajectory-Defiant Trajectory-OCP | 18 | 1 |
Farchione et al. (2007) | Target: 300 Control: 169 | Cross-sectional | America | Target: Both (52%) Control: Both (44%) | Target: 12.1 (3.6) Control: 11.6 (3.5) | – | – | Parent: CHI Self: CHI | Aggression Hostility | 16 | 1 |
Fernandez de la Cruz et al. (2015) | 579 | Cross-sectional | America | Both (80%) | 8.5 (0.8) | – | – | Parent SNAP | Withdrawn Somatic complaint Anxious/depression Social problems Thought problems Attention problems Aggressive behavior Internalizing scale Externalizing scale | 15 | 1 |
Filippi et al. (2020) | 291 | Cross-sectional | America | Both (46%) | 2–12 | – | – | Parent: ARI (12y) Self: ARI (12y) | Social Anxiety | 15 | 1 |
Gadow & Drabick (2012) | 1127 | Cross-sectional | America | Both (70%) | 12.1 (3.4) | – | – | Parent: CASI-4R Teacher: CASI-4R | ODD ADHD (inattentive) ADHD (hyperactive) CD GAD OCD Social anxiety Depressive symptom Manic | 16 | 1 |
Galano et al. (2023) | T1: 120 T2: 71 T3: 68 | Longitudinal | America | T1: Both (50%) T2: Both (54%) T3: Both (57%) | 4.94 (0.85) | + 6–8 months | 12.46 (1.77) | Parent: CBCL | Internalizing Externalizing Emotion Regulation Prosocial Behaviour | 18 | 3 |
Grabell et al. (2020) | 79 | Cross-sectional | America | Both (52%) | 3–7 | – | – | Parent: MAP-DB | Externalizing | 14 | 1 |
Guzick et al. (2021) | 161 | Cross-sectional | America | Both (51%) | 7–17 | – | – | Parent: CBCL | Depressive symptoms Anxiety OCD | 16 | 1 |
Harima et al. (2022) | 116 | Cross-sectional | Japan | Boys | 11.8 (2.6) | – | – | Self & Parent Clinical Interview | Internalizing Externalizing Anxiety/Depression | 20 | 1 |
Hawes et al. (2020) | T1: 941 T2: 941 T3: 816 | Longitudinal | America | T1: Both (43%) T2: Both (43%) T3: Both (41%) | 16.6 (1.2) | 24 | 30 | Self: K-SADS | Depressive disorder Anxiety disorders Substance use disorder | 18 | 6 |
Kahle et al. (2021) | T1:108 T2: 80 | Longitudinal | America | T1: Both (67%) T2: Both (60%) | 12–16 | 13–17 | – | Parent: CPRS-3 | Hyperactivity /Impulsivity Inattention | 19 | 5 |
Kalvin et al. (2021) | 81 | Cross-sectional | America | Both (76%) | 8–16 | – | – | Parent: ARI | Autism | 16 | 1 |
| 541 | Longitudinal | America | Both (57%) | 3.55 (0.43) | 12.75 (0.50) | – | Parent: PAPA | Internalizing Externalizing | 17 | 2 |
Kessel et al., (2017) | 338 | Cross-sectional | America | Both (56%) | 3 | – | – | Parent: PAPA | Depression Anxiety Disruptive Behavior Disorder | 17 | 1 |
Kessel et al. (2016) | T1: 541 T2: 304 | Longitudinal | America | Both (57%) | 3.55 (0.43) | 9.14 (0.32) | – | Parent: PAPA | Internalizing Externalizing | 16 | 2 |
Khurana et al. (2023) | 142 | Cross-sectional | America | Both (58%) | 10.51 | – | – | Self: ARI | Depression Suicidality | 19 | 1 |
Kishida et al. (2022) | 1867 | Cross-sectional | Japan | Both (53%) | 10.53 (2.63) | – | – | Parent: ARI | Emotional symptoms Conduct problems Hyperactivity/Inattention Peer relationship problems Prosocial behavior | 17 | 1 |
Kolko et al., (2007) | 242 | Cross-sectional | America | Both (80%) | 9.1 (2.0) | – | – | Parent: SCAR-H Teacher: SCAR-S | Aggression | 17 | 1 |
Kolko & Pardini (2010) | 177 | Cross-sectional | America | Both (81%) | 6–11 | – | – | Parent & Self: K-SADS | Global functioning Overall impairment ADHD Conduct Disorder CU traits ODD (hurtful) ODD (headstrong) | 17 | 1 |
Krieger et al. (2013) | 2514 | Cross-sectional | Brazil | Both (54%) | 6–12 | – | – | DAWBA | Emotional disorders Anxiety disorder Major depression Conduct Disorder ADHD Peer problems Pro-sociality | 18 | 1 |
Leadbeater & Ames (2017) | 662 | Longitudinal | Canada | Both (48%) | 15.5(1.9) | 26.8 | – | Parent: BCFPI | Internalizing symptoms Conduct problems ADHD symptoms | 19 | 6 |
Lee et al. (2023) | 285 | Longitudinal | Taiwan | Both (49%) | 9.9 (0.6) | 6 months later | 9 months later | Parent: CBCL | Anxiety | 19 | 3 |
Legenbauer et al. (2018) | 91 | Cross-sectional | Germany | Both (30%) | 13.98 (1.31) | 26.8(2.0) | – | Self: ARI | Affective dysregulation | 17 | 1 |
Leibenluft et al. (2006) | T1: 776 T2: 776 T3: 717 | Longitudinal | America | Both (50%) | 13.8 (2.6) | 16.2 (2.8) | – | Parent: DISC Self: DISC | ADHD Conduct Disorder ODD Depression GAD OCD Simple phobia Social phobia Mania | 17 | 5 |
Leigh et al. (2020) | T1: 165 T2: 156 | Cross-sectional | England | Both (57%) | 12–14 | – | – | Self: ARI | Depressive rumination Angry rumination | 14 | 1 |
Lengua (2006) | T1: 214 T2: 204 | Longitudinal | America | Both (45%) | 9.48 (1.01) | + 3 years | – | Parent: EATQ | Internalizing Externalizing | 17 | 3 |
Lengua & Kovacs (2005) | 92 | Longitudinal | America | Both (54%) | 7.8–11.9 | 9–13 | – | Self: EATQ Parent: EATQ | Internalizing symptoms Externalizing symptoms | 16 | 3 |
Levy et al. (2020) | 1516 | Cross-sectional | Canada | Both (74%) | 9.00 (2.19) | – | – | Parent: OCHS-R | Suicidality | 16 | 1 |
Liu et al. (2024) | 535 | Cross-sectional | China | Both (51%) | 10.01 (1.42) | – | – | Self: EATQ-R | Depression | 18 | 1 |
Loram et al., (2021) | 82 | Cross-sectional | Australia | Both (88%) | 14.33 (1.38) | – | – | Parent: ARI Self: ARI | ADHD | 18 | 1 |
Maire et al. (2020) | 98 | Cross-sectional | France | Both (81%) | 7–11 | – | – | Parent: CPRS-3 | Inattention Hyperactivity Opposition Anxiety | 16 | 1 |
Martin et al. (2017) | 139 | Cross-sectional | America | Both (76%) | 4–5 | – | – | Parent: DIPA | Emotionally reactive Anxious/depressed Withdrawn Attention problems Aggressive behavior ODD MDD ADHD Anxiety disorder PTSD | 16 | 1 |
Mikolajewski et al. (2017) | 2450 | Longitudinal | America | Both (49%) | 11.38 | 17 | – | Parent: DICA-R | Internalizing symptoms MDD Externalizing symptoms Specific phobia Panic disorder Adult antisocial behavior Alcohol use disorder | 17 | 3 |
Mulraney et al. (2014) | 62 | Cross-sectional | Australia | Both (39%) | 15.29 (1.32) | – | – | Parent: ARI | Emotional problems Conduct problems Hyperactivity Peer problems Prosocial | 12 | 1 |
Mulraney et al. (2017) | 140 | Longitudinal | Australia | Both (89%) | 5–13 | 12–17 | – | Parent: ARI Self: ARI | ADHD | 14 | 3 |
Naim et al. (2021) | 109 | Cross-sectional | America | Both (72%) | 8–18 | – | – | Parent: ARI Self: ARI | DMDD ADHD Anxiety | 16 | 1 |
Nelson et al. (2018) | 69 | Cross-sectional | America | Both (37%) | 9–14 | – | – | Parent: ARI Self: ARI | Anxiety Depression Stress | 17 | 1 |
Pan & Yeh (2019) | 97 | Cross-sectional | Taiwan | Both (73%) | 6–17 | – | – | Parent: ARI Self: ARI | Aggression Anxiety/depression Social problems | 15 | 1 |
Perhamus & Ostrov (2021) | 300 | Longitudinal | America | Both (56%) | 3.7(0.37) | 7 | – | Parent: CBQ-TF | Reactive physical aggression Proactive physical aggression | 18 | 2 |
Poznanski et al. (2018) | 435 | Cross-sectional | America | Both (47%) | 12.7 (3.0) | – | – | Parent: CBCL | Anxiety severity Depressive disorder severity Sleep problems ADHD/DBD severity | 17 | 1 |
Rappaport et al. (2020) | 374 | Cross-sectional | America | Not reported | 9–14 | – | – | Self: ARI | Depression GAD Separation anxiety Social anxiety Panic disorder symptoms | 14 | 1 |
Rice et al. (2017) | 337 | Cross-sectional | England | Both (42%) | 12.4 (2.00) | 14 | – | CAPA | Depression | 15 | 1 |
Rowe et al. (2010) | 1420 | Longitudinal | America | Both (56%) | 9–13 | 13–16 | – | Parent: CAPA | Conduct Disorder ODD Substance use disorder Anxiety Depression | 16 | 3 |
Rubens et al. (2017) | 285 | Cross-sectional | America | Both (48%) | 8–11 | – | – | Self: ARI | Anxiety Depression Emotion dysregulation Delinquency Reactive aggression Proactive aggression | 15 | 1 |
Silver et al. (2021) | 550 | Longitudinal | America | Girls | 14.37 (0.62) | + 3 years | – | Self: IPIP, BPAQ, TAI | Depression Panic disorder GAD Social phobia Specific phobia ODD Conduct Disorder Substance use disorder | 16 | 3 |
Silver et al. (2024) | 418 | Cross-sectional | America | Both (57%) | 12.66 (0.46) | 15.25 (0.41) | 18.37 (0.54) | Self: ARI Parent: ARI | Suicidal ideation Depressive disorder Anxiety disorder DBD ADHD | 20 | 1 |
Smith et al. (2019) | 731 | Longitudinal | America | Both (51%) | 2–5 | 7.5 – 10.5 | – | Parent: CBCL | Externalizing Internalizing ODD GAD MDD | 14 | 2 |
Sorcher et al. (2022) | 212 | Longitudinal | America | Both (53%) | 3.51 (0.26) | 15.25 (0.40) | – | Parent: PAPA | Depression Anxiety Specific phobia Social phobia Separation anxiety GAD ADHD DBD Self-harm Suicidal ideation Global functioning | 16 | 2 |
Srinivasan et al., (2024) | 7225 | Longitudinal | England | Both (49%) | 3 | 5 | 14 | SDQ CSBQ | Depressive symptoms | 18 | 2 |
Stoddard et al. (2017) | 115 | Cross-sectional | England | Both (56%) | 8–17 | – | – | Parent: ARI | Anxiety | 16 | 1 |
Stringaris & Goodman (2009a) | Total:18,298 4278 (Parent) 14,020 (Teacher) | Cross-sectional | England | Both (57%) Both (50%) | 10.4 (3.3) 10.6 (3.2) | – | – | Parent: DAWBA Teacher: DAWBA | Emotional problems Hyperactivity Conduct problem Peer problems | 18 | 1 |
Stringaris & Goodman (2009b) | 7912 | Longitudinal | England | Both (52%) | 10.2 (3.3) | 13.2 (3.3) | – | Parent: DAWBA | Internalizing disorders ADHD Conduct Disorder Distress disorders | 16 | 3 |
| 306 | Longitudinal | England | Both (42%) | 15 | 17 | – | Self ASEBA | Depression Delinquency | 18 | 5 |
Theriault et al. (2018) | 58 | Longitudinal | Canada | Both (85%) | 10.3 (2.6) | 19.7 (2.5) | – | Parent: DSM-IV clinician interview | Chronic tic and anxiety Chronic tic and compulsive symptoms | 18 | 6 |
Ucar & Vural (2018) | 86 | Cross-sectional | Turkey | Both (68%) | 13.72 (1.34) | – | – | Parent: ARI Self: ARI | ADHD | 16 | 1 |
Valencia et al. (2021) | 470 | Longitudinal | Spain | Both (50%) | 8 | 11 | – | Parent: SDQ | Internalizing symptoms | 17 | 2 |
Vogel et al. (2019) | 302 | Longitudinal | America | Both (52%) | 3–5 | 16–19 | – | Parent: PAPA | ADHD ODD Conduct disorder | 14 | 3 |
Wakschlag et al. (2015) | 497 | Longitudinal | America | Both (50%) | 2.9—6 | 3.1 – 7.7 | 3.8 – 8.5 | Parent: MAP-DB Temper loss scale | ODD symptoms CD symptoms ADHD symptoms Depression symptoms GAD symptoms Social anxiety symptoms | 19 | 2 |
Wakschlag et al. (2020) | 151 | Cross-sectional | America | Both (53%) | 4.82 (0.60) | – | – | Parent: MAP-DB Temper loss scale | Internalizing Externalizing | 15 | 1 |
Wang et al. (2023) | 323 | Longitudinal | China | Both (50%) | 8.29 (0.47) | 1 year later | 2 years later | Parent: CBQ | GAD | 18 | 3 |
Waschbusch et al. (2020) | 219 | Cross-sectional | America | Both (79%) | 9.53 (1.57) | – | – | Parent & Teacher (Combined): DBDRS | Psychopathology Aggression Peer problems Impairment | 14 | 1 |
Waxmonsky et al. (2022) | 48 | Cross-sectional | America | Both (69%) | 8.08 (2.09) | – | – | Parent: ARI | ADHD ODD CD Callous-unemotional | 17 | 1 |
Waxmonsky et al. (2017) | S1: 665 S2: 784 Total: 1449 | Cross-sectional | America | S1: Both (53%) S2: Both (68%) | 6–12 | – | – | Parent: PBS | Oppositional behavior Hyperactive-Impulsive Conduct problem Anxiety Depression Inattention | 17 | 1 |
Whelan et al. (2015) | 3963 | Longitudinal | United Kingdom | Not reported | 2 | 10 | 13 | Mother & Teacher: DAWBA | Anxiety/depression Conduct problems Depression at 16y | 19 | 3 |
Wiggins et al. (2023) | 425 | Longitudinal | America | Both (49%) | 4.7 (0.85) | 7.1 (1.1) | 9.3 (0.79) | Parent: MAPS-TL | Any disorder Externalizing Internalizing | 16 | 2 |
Wilson et al. (2022) | 115 | Cross-sectional | America | Both (48%) | 5.56 (1.7) 3–8 | – | – | Parent: ARI | Anxiety Anxious/depressed Aggression Attention | 17 | 1 |
Zendarski et al. (2023) | 51 | Cross-sectional | Australia | Both (53%) | 11.17 (2.5) | | | Parent: ARI Self: ARI | Internalizing Externalizing ADHD ASD | 18 | 1 |
Zhou et al. (2009) | S1: 382 S2: 322 Total: 704 | Cross-Sectional | Chinese/USA | S1: Both (44%) S2: Both (47%) | S1: 11.6 (0.6) S2: 9.6 (1.0) | – | – | S1 Parent/ Teacher: CBQ S2 Parent/ Teacher: EATQ | Attention Externalizing Internalizing | 18 | 1 |
Zik et al. (2022) | 195 | Cross-sectional | America | Both (59%) | 13.16 (2.48) | – | – | Parent: ARI Self: ARI | Aggression Anger | 16 | 1 |
Concurrent Associations (Model 1)
Irritability and overall mental health symptoms. The analysis of studies reporting concurrent data showed a positive association between irritability and overall mental health symptoms, k = 417, r = 0.33 (95% CI 0.29, 0.36). Forest and Funnel plots are available as supplementary materials (Fig. S6a and S6b). Egger’s regression was non-significant, indicating no publication bias, t(415) = 1.23, p = 0.22. Heterogeneity was found across the models, I2 > 98, with a significant Q statistic, thereby supporting further tests of potential moderators. For studies reporting on concurrent associations, study quality was significant k = 417, χ2(1) = 4.45, p = 0.03, R2 = 0.01, indicating that as the study quality increased, the association between irritability and mental health decreased (see Supplementary file, Figure S6c). Other moderators were non-significant: age (k = 417, χ2(1) = 0.33, p = 0.56, R2 = 0.00); informant type (k = 417, χ2(5) = 9.92, p = 0.07, R2 = 0.02), and sex (k = 412, χ2(1) = 1.79, p = 0.18, R2 = 0.00). A sensitivity analysis was conducted to examine whether results varied according to measure of irritability. The fixed effects model (k = 417, r = 0.31 (95% CI 0.31, 0.31)) and the random effect models (k = 417, r = 0.28 (95% CI 0.26, 0.29)) did not differ significantly (p = 0.64), indicating that the measure of irritability did not significantly influence the results.
Irritability and externalizing/internalizing symptoms. Analysis of concurrent data showed a positive association between irritability and internalizing symptoms k = 189, r = 0.29 (95% CI 0.27, 0.32), and a positive association with externalizing symptoms, k = 181, r = 0.37 (95% CI 0.31, 0.43). In meta-regression testing symptom dimensions as moderators, the effect size for externalizing symptoms was significantly greater than for internalizing symptoms k = 370, χ2(1) = 4.21, p = 0.04, R2 = 0.01 (see Supplementary file, Fig. S6d).
Irritability and diagnostic domains. Subgroup analysis conducted on effect sizes for concurrent associations between irritability and diagnostic domains were as follows: anxiety, k = 73, r = 0.22 (95% CI 0.21, 0.23); depression, k = 47, r = 0.28 (95% CI 0.27, 0.29); ADHD, k = 77, r = 0.26 (95% CI 0.20, 0.31); ASD, k = 6, r = 0.10 (95% CI − 0.01, 0.21); CD, k = 23, r = 0.36 (95% CI 0.35, 0.37); ODD, k = 29, r = 0.63 (95% CI 0.63, 0.64); SUD k = 2, r = 0.49 (95% CI− 0.40, 0.58); and OCD, k = 5, r = 0.14 (95% CI 0.09, 0.18). Meta-regression showed that the effect size for ODD was significantly greater than other diagnostic domains, k = 260, χ2(6) = 94.25, p = 0.00, R2 = 0.28 (see Supplementary file, Fig. S6e).
Longitudinal Associations: Preschool to Middle Childhood (Model 2)
Irritability and overall mental health symptoms. The analysis of longitudinal studies showed a positive association between preschool irritability and overall mental health symptoms in middle childhood, k = 65, r = 0.21 (95% CI 0.18, 0.24). Forest and Funnel plots are available as supplementary materials (Figure S6f and S6g). Egger’s regression was significant, indicating publication bias, t(63) = 7.39, p = 0.00. Heterogeneity was found across the models, I2 > 85 and the Q statistic significant, thereby supporting tests of potential moderators. Age (k = 65, χ2(1) = 0.03, p = 0.87, R2 = 0.00), sex (k = 65, χ2(1) = 0.58, p = 45, R2 = 0.0), study quality (k = 65, χ2(1) = 1.27, p = 0.32, R2 = 0.01) and informant type (k = 65, χ2(3) = 5.60, p = 0.13, R2 = 0.01) were tested as moderators and found to be non-significant. Due to the small number of measures of irritability in these studies, a moderation analysis, rather than sensitivity analysis, was conducted to examine variation based on type of measure. The model was also non-significant (k = 65, χ2(6) = 11.32, p = 0.08, R2 = 0.18), indicating that factors other than measurement type, age, sex, study quality, and informant type may account for heterogeneity in the model.
Irritability and externalizing/internalizing symptoms. A subgroup analysis of preschool irritability and mental health outcomes in middle childhood indicated comparable effect sizes for internalizing symptoms k = 26, r = 0.18 (95% CI 0.13, 0.22) and externalizing symptoms, k = 30, r = 0.23 (95% CI 0.18, 0.27). Meta-regression analysis testing these symptom dimensions as moderators showed no significant difference (k = 56, χ2(1) = 2.64, p = 0.10, R2 = 0.05).
Irritability and diagnostic domains. In a subgroup analysis conducted on the association between preschool irritability and middle childhood diagnostic domains, effect sizes were as follows: anxiety k = 8, r = 0.11 (95% CI 0.07, 0.14); depression, k = 9, r = 0.13 (95% CI 0.06, 0.20); ADHD, k = 9, r = 0.16 (95% CI 0.10, 0.23); CD, k = 6, r = 0.22 (95% CI 0.10, 0.35); and ODD, k = 6, r = 0.25 (95% CI 0.19, 0.31). Meta-regression found a significant difference across diagnostic domains (k = 38, χ2(1) = 11.59, p = 0.02, R2 = 0.29), whereby effect sizes for CD were larger than for anxiety (see Supplementary file, Fig. S6h).
Longitudinal Associations: Middle Childhood to Late Childhood/Adolescence (Model 3)
Irritability and overall mental health symptoms. This analysis showed a positive association between irritability in middle childhood and mental health symptoms in later childhood/adolescence, k = 39, r = 0.14 (95% CI 0.11, 0.17). Forest and Funnel plots are available as supplementary materials (Figure S6i and S6j). Egger’s regression was significant, indicating publication bias, t(37) = 2.54, p = 0.00. Heterogeneity was found across the models, I2 > 85 and the Q statistic significant, thereby supporting tests of potential moderators. Age (k = 39, χ2(1) = 0.56, p = 0.46, R2 = 0.02), sex (k = 38, χ2(1) = 0.52, p = 0.47, R2 = 0.00), study quality (k = 39, χ2(1) = 3.63, p = 0.06, R2 = 0.11), and informant type (k = 34, χ2(1) = 3.88, p = 0.27, R2 = 0.08), were tested as moderators and found to be non-significant. Due to the small number of measures of irritability in these studies, a moderation analysis, rather than sensitivity analysis, was conducted to examine variation based on type of measure. The model was significant (k = 29, χ2(9) = 26.64, p = 0.00, R2 = 0.55), indicating that effect sizes for studies using the Affective Reactivity Index (ARI) were significantly larger than those using the CBQ, DAWBA, DICA, DISC, the Disruptive Behavior Disorder Checklist (DBDC), the Child and Adolescent Psychiatric Assessment (CAPA), and the Strengths and Difficulties Questionnaire (SDQ) (see Supplementary file, Figure S6k).
Irritability and externalizing/internalizing symptoms. Effect sizes were as follows for externalizing, k = 10, r = 0.13 (95% CI 0.03, 0.22), and internalizing symptom dimensions, k = 25, r = 0.14 (95% CI 0.10, 0.18). Meta-regression analysis testing these symptom dimensions as moderators showed no significant difference (k = 35, χ2(1) = 0.04, p = 0.85, R2 = 0.00).
Irritability and diagnostic domains. In a subgroup analysis conducted on the association between middle childhood irritability and diagnostic domains in later childhood/adolescence, effect sizes were as follows: anxiety, k = 12, r = 0.14 (95% CI 0.08, 0.19); depression, k = 13, r = 0.15 (95% CI 0.09, 0.20); CD, k = 4, r = 0.14 (95% CI − 16., 0.41); and ODD, k = 4, r = 0.16 (95% CI 0.04, 0.26). Meta-regression indicated no significant differences between diagnoses k = 36, χ2(5) = 0.30, p = 0.99, R2 = 0.01.
Longitudinal Associations: Middle Childhood to Adulthood (Model 4)
Irritability and overall mental health symptoms. This model could not be run due to insufficient data. Available data were integrated with model 6.
Longitudinal Associations: Early Adolescence to Late Adolescence (Model 5)
Irritability and overall mental health symptoms. A positive association was found between irritability in early adolescence and mental health symptoms in later adolescence, k = 11, r = 0.21 (95% CI 0.15, 0.28). Forest and Funnel plots are available as Supplementary materials (Fig. S6l and S6m). Egger’s regression was significant, indicating potential publication bias, t(9) = 2.95, p = 0.02. Heterogeneity across the models, I2 > 60, and a significant Q statistic, supported moderation analysis. Age was found to be a significant moderator, k = 11, χ2(1) = 12.00, p = 0.00, R2 = 0.93 (see Supplementary file, Fig. S6n), such that as age increased, the effect size for overall mental health symptoms was larger. Informant type (youth self-report; parent report) was significant, k = 11, χ2(1) = 12.00, p = 0.00, R2 = 0.93 (see Supplementary file, Fig. S6o), whereby effect sizes for youth self-reports were larger than parent-reports. A significant moderation effect was also found for sex, k = 11, χ2(1) = 8.35, p = 0.00, R2 = 0.88, indicating smaller effects for samples with more boys (see Supplementary file, Fig. S6p). No moderator effect was found for study quality (k = 11, χ2(1) = 1.00, p = 0.32, R2 = 0.27).
Due to the small number of measures of irritability in these studies, a moderation analysis, rather than sensitivity analysis, was conducted to examine variation based on type of measure. The model was significant (k = 11, χ2(2) = 12.02, p = 0.00, R2 = 0.93), indicating that effect sizes for studies using the ASEAB were significantly greater than those using the DISC in this age group (see Supplementary file, Figure S6q).
Irritability and externalizing/internalizing symptoms. Effect sizes were as follows for externalizing, k = 4, r = 0.27 (95% CI 0.23, 0.31) and internalizing symptom dimensions, k = 5, r = 0.17 (95% CI 0.03, 0.31). The number of available studies was not sufficient for meta-regression analysis.
Irritability and diagnostic domains. In a subgroup analysis conducted on the association between irritability and diagnostic domains, effect sizes were as follows: anxiety, k = 3, r = 0.11 (95% CI − 0.02, 0.38); depression, k = 2, r = 0.27 (95% CI 0.09, 0.43); ADHD k = 2, r = 0.17 (95% CI − 0.06, 0.38); CD, k = 1, r = 0.19 (95% CI − 16, 0.41); and ODD, k = 2, r = 0.25 (95% CI − 0.02, 0.49). A meta-regression conducted with ODD as the intercept indicated a significant difference compared to anxiety k = 10, χ2(4) = 19.16, p = 0.01, R2 = 1.00 (see Supplementary File S6r).
Longitudinal Associations: Adolescence to Adulthood (Model 6)
Irritability and overall mental health symptoms. A positive association was found between irritability in adolescence and mental health symptoms in adulthood, k = 9, r = 0.25 (95% CI 0.12, 0.37). Forest and Funnel plots are available as Supplementary materials (Figure S6s and S6t). Egger’s regression was significant, suggesting publication bias, t(7) = 2.23, p = 0.06. The number of available studies was not sufficient for meta-regression analysis.
Irritability and externalizing/internalizing symptoms. Effect sizes were as follows for externalizing, k = 3, r = 0.39 (95% CI 0.32, 0.46), internalizing symptom dimensions, k = 5, r = 0.05 (95% CI − 0.00, 0.09). The number of available studies was not sufficient for meta-regression analysis.
Irritability and diagnostic domains. No subgroup analysis was conducted due to insufficient data.
Discussion
Evidence regarding irritability and mental health has grown rapidly in recent years, and the current meta-analysis is the first to examine irritability across childhood and adolescence as it relates to mental health symptoms during these periods. Findings demonstrated a significant and positive association between irritability and severity of concurrent overall psychopathology in the order of a moderate effect size, while small to moderate effect sizes characterized the association between irritability and later mental health outcomes in studies with prospective designs. Notwithstanding the significant relationship between irritability and overall severity of mental health symptoms, this association was also found to differ somewhat according to symptom type. This was evident both at the level of broad dimensions of internalizing versus externalizing symptoms, as well as symptom domains based on more specific diagnostic categories.
The association between irritability and concurrent problem severity was most pronounced for externalizing problems, which demonstrated a significantly greater association with irritability than internalizing problems in concurrent data. Data on concurrent associations are particularly relevant to the conceptualization of irritability in diagnostic models, especially models of disorders in which irritability forms a core phenotypic feature (Evans et al.,
2021a). When externalizing problems were broken down further into more distinct diagnostic domains, symptoms of ODD showed the most pronounced association with irritability, relative to other diagnostic domains including CD. This is understandable given that diagnostic criteria for ODD include an angry/irritable mood symptom dimension (APA,
2013), and factor analytic research has provided strong support for the inclusion of this dimension in the overall structure of ODD (Burke et al.,
2014).
Prospectively, irritability was associated with greater mental health symptoms across each of the developmental periods examined. Consistent with the data on concurrent associations, and the conceptualization of irritability as a transdiagnostic construct, these positive longitudinal associations were seen for both externalizing and internalizing symptoms. Prospective associations between irritability and each of these broad symptom dimensions were highly comparable, yet these prospective associations were once again more prominent for diagnostic features of externalizing problems, in terms of ODD and CD specifically. This is noteworthy given that current diagnostic criteria for CD do not explicitly refer to irritability. It is nonetheless consistent with evidence regarding the highly overlapping nature of the symptoms represented by ODD and CD, which have been conceptualized as part of a broader externalizing spectrum also encompassing ADHD, substance use disorder, and antisocial personality disorder. Although irritability is often not explicitly named in the diagnostic criteria for these disorders, all are understood to be associated with irritability. Moreover, irritability is implicated in the common liabilities from which these disorders are thought to arise, such as trait impulsivity (Lahey et al.,
2011). In terms of the neurodevelopmental underpinnings of such impulsivity, it has been proposed that irritability reflects a chronically aversive mood state driven by subcortical dysfunction in the mesolimbic dopamine system, which in turn motivates individuals to engage in reward-seeking behaviors (Beauchaine et al.,
2017).
As a transdiagnostic factor that is understood to reflect emotion dysregulation, irritability may help explain the high rates of comorbidity between diverse forms of internalizing and externalizing disorders in the population. CD for example, frequently co-occurs with depression and anxiety, particularly among girls (Fairchild et al.,
2019). Emerging research has pointed to mechanisms that may account for the diverse forms of psychopathology that arise from the common starting point of irritability, reflecting the principle of multifinality in developmental psychopathology. For example, variations in stress system functioning (diurnal cortisol slopes) have been found to differentiate developmental trajectories of early childhood irritability that lead to internalizing versus externalizing symptoms in early adolescence (Kessel et al.,
2021).
Interestingly, in our data the specific pattern of prospective associations with diagnostic features varied somewhat across distinct developmental periods, such that early childhood irritability was more strongly associated with features of CD across middle childhood, whereas irritability in early adolescence was most strongly associated with features of ODD across adolescence. This raises important questions regarding developmental changes in the relationship between irritability and distinct risk pathways over time. These findings could be seen as analogous to the notion that distinct dimensions of ODD symptoms, including irritable mood, may vary in relation to one another across development, as has been subject to some speculation (Burke & Loeber,
2010). Although research testing this directly has generally supported the structural invariance of ODD dimensions across development (Jungersen & Lonigan,
2022; Lavigne et al.,
2015), further investigation is warranted. There is a particular need for further longitudinal studies of irritability in late childhood and early adolescence as a predictor of subsequent mental health symptoms across adolescence and early adulthood, given that the number of such studies currently available precluded tests of moderation by symptom type across these periods.
In addition to the developmental perspective provided by these results, our tests of age as a moderator variable provided some evidence that irritability may become more strongly associated with overall mental health problems as children and adolescents get older. Specifically, within adolescence (age range 13–18 years), an older age was associated with a larger effect size. This should be interpreted with caution, however, as it may in part reflect that the testing interval for older adolescents would have been shorter than for younger adolescents in this model. Based on the broad range of neurocognitive domains that have been implicated in irritability-related risk mechanisms (e.g., cognitive control; reward processing; Elvin et al.,
2024), it is important to consider how cog-nitive development may influence the relationship between irritability and symptoms of psychopathology. Recent research has identified developmental trajectories of irritability that appear to be differentially associated with clinical outcomes, and there is a need for further developmental research into the multilevel (e.g., cognitive, genetic, environment) mechanisms underlying these trajectories (Leibenluft et al.,
2024).
Our search indicated a need for research to investigate irritability as a distinct treatment outcome variable, which remains limited to date. Considerable support is nonetheless available for the effects of parenting interventions on irritability within the symptom profile of ODD (Hawes et al.,
2023, Stringaris et al.,
2018). Recent research has also supported the potential for such intervention, and cognitive behavior therapy, to reduce transdiagnostic features of irritability in the context of modular approaches (Evans et al.,
2021b). Emerging evidence regarding interplay between child characteristics and environmental factors such as quality of parenting further suggests that irritability may be implicated in a temperament profile associated with differential susceptibility to the environment (Belsky et al.,
2007). For example, children with a profile characterized by temperamental traits of high irritability, approach, activity, and impulsivity appear to be more vulnerable to externalizing problems when exposed to negative maternal parenting, compared to children without this profile, but these same children also appear to benefit more than other children when exposed to positive maternal parenting (Hentges et al.,
2023). Moreover, irritability may in some instances reflect a vantage sensitivity, accounting for individual differences in response to parenting interventions (de Villiers et al.,
2018).
The findings of our meta-analysis should be interpreted in light of some limitations. First, the studies from which data were extracted were conducted largely in Western, educated, industrialized, rich, and democratic (WEIRD) populations (Henrich et al.,
2010), and therefore generalizability of results across cultures and regions is unclear. Populations from Asia and Africa were particularly under-represented. Second, the funnel plots produced for our models indicated some risk of publication bias, suggesting that the overall effect sizes produced may be somewhat inflated. Third, like the meta-analytic review by Finlay-Jones et al. (
2024), our literature search was limited to English-language publications. Finally, heterogeneity estimates were high for many of the models tested, which may be due to diverse measures of irritability used across studies, in addition to inconsistent approaches to controlling for factors such as age, sex, and baseline mental health symptoms. Notwithstanding these limitations, our design and methodology reflects strengths including a specific focus on studies that have indexed irritability in isolation from overlapping constructs such as negative emotionality, and the examination of the construct across childhood and adolescence. One of the most common measures of irritability across these studies was the Affective Reactivity Index, as recognized in DSM-5 as a gold-standard measure of the construct, and our meta-analysis is the first to include the extensive child and adolescent research that has been conducted with this measure in the past decade.