Phasic Versus Tonic Irritability: Differential Associations With Attention-Deficit/Hyperactivity Disorder Symptoms

Abstract

Objective: Irritability is a multifaceted construct in pediatric psychopathology. It has been conceptualized as having a phasic dimension and a tonic dimension. Disruptive mood dysregulation disorder is defined by the presence of both dimensions. Severe irritability, or disruptive mood dysregulation disorder, is highly comorbid with attention-deficit/hyperactivity disorder (ADHD). However, it is unknown whether the presence of ADHD modulates the expression of phasic and tonic irritability.

Method: A data-driven, latent variable approach was used to examine irritability and ADHD symptoms in a transdiagnostic pediatric sample (N = 489) with primary disruptive mood dysregulation disorder, ADHD, subclinical irritability symptoms, or no diagnosis. Using latent profile analyses, we identified 4 classes: high levels of both irritability and ADHD symptoms, high levels of irritability and moderate levels of ADHD symptoms, moderate levels of irritability and high levels of ADHD symptoms, and low levels of both irritability and ADHD symptoms. Confirmatory factor analysis operationalized phasic irritability and tonic irritability.

Results: As expected, the 2 latent classes characterized by high overall irritability exhibited the highest levels of both phasic and tonic irritability. However, between these 2 high irritability classes, highly comorbid ADHD symptoms were associated with significantly greater phasic irritability than were moderately comorbid ADHD symptoms. In contrast, the 2 high irritability groups did not differ on levels of tonic irritability.

Conclusion: These findings suggest that phasic, but not tonic, irritability has a significant association with ADHD symptoms and that phasic and tonic might be distinct, though highly related, irritability dimensions. Future research should investigate potential mechanisms underlying this differential association.

Trial registration: ClinicalTrials.gov NCT00018057.

Keywords: ADHD; DMDD; aggression; irritability; latent variable analysis.

FIGURE 1. Mean Scores on the Symptom Measures for Each Class in the 4-Class Solution

Note: Irritability as measured by the parent report Affective Reactivity Index (ARI), CBRS Inattentive and CBRS Hyperactive/Impulsive as measured by the DSM Inattentive and Hyperactive/Impulsive subscales of the Conners Comprehensive Behavior Rating Scale. z-score of 1 = ARI Parent score of 8.52, Conners CBRS Inattentive score of 19.08, and Conners CBRS Hyperactive/Impulsive score of 15.29; z-score of 0 = ARI Parent score of 4.38, Conners CBRS Inattentive score of 10.55, Conners CBRS Hyperactive/Impulsive score of 7.88; z-score of −1 = ARI Parent score of 0.23, Conners CBRS Inattentive score of 2.02, and Conners CBRS Hyperactive/Impulsive score of 0.46. ADHD = attention-deficit/hyperactivity disorder.

FIGURE 2. Confirmatory Factor Analysis Models for Temper Outbursts, Aggression, and Irritable Mood Between Outbursts

Note: (A) temper outbursts, (B) aggression, and (C) irritable mood between outbursts. Path coefficients represent the loading of each item onto the latent factor. DMDD = disruptive mood dysregulation disorder; RMOAS = Retrospective Modified Overt Aggression Scale; SCAR-H = Screen for Children’s Affective Reactivity–Home; STAXI = State-Trait Anger Expression Inventory. ***p < .001.

FIGURE 3. Estimated Marginal Means for Temper Outbursts, Aggression, and Irritable Mood Between Outbursts Factor Scores Across Each Class in the 4-Class Solution

Note: Error bars represent 95% CI. The only nonsignificant pairwise comparison was for irritable mood between outbursts scores between the high irritability + high ADHD and high irritability + moderate ADHD groups. ADHD = attention-deficit/hyperactivity disorder; ns = nonsignificant.