The aim of the current study was to evaluate the feasibility, acceptability, and effectiveness of Dialectical Behavioral Therapy-based skills training groups for adults with ADHD in an outpatient psychiatric context. Furthermore, the purpose was to analyze the impact of clinical characteristics on the effect and attrition. Ninety-eight adults (out of 102) with ADHD were allocated to the treatment. Self-rating scales were administered as baseline before the first session (T1), post-treatment (T2), and at 3-month follow-up (T3). Approximately 80 % (74 individuals) attended at least two-thirds of the sessions. Treatment satisfaction was good. ADHD symptoms and ADHD-related functional impairment in every-day life were reduced. Well-being, ability to be mindful, acceptance of emotions and quality of life were increased. The results were stable at 3-month follow-up. None of the predictors, i.e., age, comorbidity, ADHD medication status, IQ-level, treatment credibility, or functional impairment at the beginning of treatment, significantly predicted treatment outcome (change in ADHD symptoms from T1 to T2). Likewise, none of the predictors, i.e., irritability/aggression, comorbidity, and functional impairment, were significantly associated with attrition. Due to the difficulties in predicting treatment outcome, as well as attrition, based on clinical characteristics, broad inclusion criteria should be applied.
Keywords: ADHD; Adults; Group therapy; Multimodal; Psychotherapy; Skills training group.