What this trial measures

• Clinician Affective Reactivity Index (CL-ARI)Bi-weekly and f/u

  A 12-item clinician-administered measure of temper outbursts, irritable mood, and impairment over the past week, based on parent and child report.

• Clinical Global Impressions Improvement (CGI-I)Relative to pre-treatment anchor and pre, mid, post and f/u

  A clinician-rated, diagnosis-independent measure of overall treatment response, assessing change from relative to a baseline on a 7-point scale (1 = very much improved to 7 = very much worse)

• CBT for Irritability-Adherence ScalePost each psychotherapy session

  The CBT for irritability- Adherence Scale was developed specifically for the exposure-based CBT treatment we developed. The measure contains 26 items focused on standard elements of cognitive behavioral therapy (e.g., setting agenda, homework, motivation), treatment-specific elements (e.g., exposure for the child and parent skills training for the parent), and mode of delivery elements (e.g., modeling, rehearsal, coaching). Each item is phrased as to the extent to which the therapist adheres to that task; for instance, Therapist encourages child participation in one or more exposure tasks. Therapist completes each measure for child and parent after each of the 12 sessions and rating each item on a 7-point scale: 1 = not at all, 4 = considerably, 7 = extensively.

• Working Alliance Inventory (WAI)Post each psychotherapy session

  The WAI (Horvath \& Greenberg, 1989) is 12-item, 7-point Likert-scale measure of alliance in the therapist-client dyad. We plan to use this measure to assess the alliance between therapist and parent. Individual item responses range from 0 ( Never ) to 6 ( Always ). Items are worded as statements on the dyadic relationship between therapist and parent. The WAI contains 3 subscales based on Bordin s (1979) analysis of the primary components of therapeutic alliance: Goal, Task, and Bond, which assess the degree to which the parent feels they agree with the therapist on the primary goals of therapy, the usefulness of the tasks completed in therapy, and feelings of trust and compatibility with the therapist, respectively. The WAI has demonstrated good reliability and validity in previous studies (Hatcher et al., 2020; Munder et al., 2010). This measure takes about 5 minutes to complete and will be administered at each session.

• Therapeutic Alliance Scale for Children-revised (TASC-r)Post each psychotherapy session

  The TASC-R (Shirk \& Saiz, 1992) is a 12-item measure of therapeutic alliance, as reported by the child. The TASC-r contains 2 subscales based on Bordin s (1979) therapeutic alliance research: Bond, or the degree to which the child feels a bond with the therapist, and Task, the child s assessment of whether therapy is a productive and collaborative endeavor (Bordin, 1979). The TASC-r scores have demonstrated good reliability and validity in previous studies (Creed \& Kendall, 2005; DeVet et al., 2003). This measure takes about 5 minutes to complete and will be administered at each session.