Effectiveness of Acceptance and Commitment Therapy on the Positive and Negative Symptoms and Emotion Regulation of Patients with Schizophrenia Spectrum Disorders: A Single-case Clinical Trial Study

 The literature suggests the increasing application of acceptance and commitment therapy (ACT) for people with schizophrenia spectrum disorders (SSD).

 This study aimed to determine the effectiveness of ACT on the positive and negative symptoms and emotion regulation of patients with SSD.

 The experimental design of the current study was an AB (baseline and intervention phases) along with the follow-up phase, in addition to Treatment-As-Usual (TAU), ACT sessions were held for the participants. Among the 20 participants who had inclusion criteria to the study, five participant (three men and two women in the age range of 32 - 43 years) were randomly allocated to participate in the intervention through drawing and evaluated using the Positive and Negative Syndrome Scale (PANSS) and Difficulties in Emotion Regulation Scale (DERS) in three phases of baseline, intervention, and follow-up. For data analysis, non-overlapping indices and Cohen's d effect size were measured, and visual diagrams were plotted for interpretation.

 The present results showed that the effect sizes of psychotic symptoms in the first to fifth participants were 1.7, 1.9, 0.6, 4, and 1.4, respectively in the intervention phase relative to the baseline; the effect size was only large for the fourth participant. Also, the effect sizes of emotion regulation in the first to fifth participants were 0.8, 1.6, 1.5, 1.2, and 2.7, respectively; the effect size was only large for the fifth participant.

 The results of data analysis showed that ACT is effective in reducing psychotic symptoms and improving emotion regulation. The effect size of ACT was the largest for the fourth participant; medium for the first, second, and fifth participants; and small for the third participant.