Supplementary Material for: Dialectical Behaviour Therapy to Treat Emotion Dysregulation in Autistic adults without Intellectual Disability: A Randomised Controlled Trial

Introduction: Emotion dysregulation is prevalent in autistic adults without intellectual disability whereby it has been associated with heightened non-suicidal self-injury and suicidal behaviours. Dialectical behaviour therapy (DBT) has shown to be feasible and preliminary findings suggest that it might reduce emotion dysregulation in this population. Yet studies evaluating the efficacy of DBT in this context are lacking.
Methods: Sixty-three autistic adults presenting with emotion dysregulation as well as self-harm and/or suicidal behaviours were randomised either to the DBT condition (18-week treatment) or to the waiting list condition. Participants completed self-report scales, including emotion dysregulation, alexithymia, depression and quality of life, at 4 time points (pre-, mid-, post-therapy, six-month follow-up).
Results: Emotion dysregulation improved in the DBT condition relative to the waiting list condition mid-therapy (β01 = -18.59 [-27.67 to -9.44], Pr (β01 < 0) = 1.000), post- therapy (β02 = -31.91 [-41.67 to -22.30], Pr (β02 < 0) = 1.000), with lasting improvements at follow-up. Alexithymia improvement mediated the therapy effects on emotion dysregulation. Moreover, depressive symptoms and quality of life improved in the DBT condition relative to the waiting list condition post-therapy, with improvements lasting at follow-up.
Conclusion: DBT was found to be effective to reduce emotion dysregulation in autistic adults presenting with self-harm and/or suicidal behaviour. Additionally, improvements on depression and quality-of-life were observed post-therapy. Interestingly, the improvements on emotion dysregulation were mediated by a decrease in alexithymia, consistent with research showing that alexithymia is a central mechanism of emotion dysregulation in autistic adults.