The results of the search are summarized in Fig. 1: 848 unique abstracts were screened; 28 full texts were reviewed; and 10 publications reporting on 11 studies met all eligibility criteria and were included in the final review. Of these 11 studies, six were RCTs and five were observational studies. Table 1 summarizes the characteristics of the 11 included studies and Table 2 summarizes their effectiveness outcomes. Additional file 1: Table S2 in the supplementary material describes the included interventions and reported feasibility and acceptability measures.

Two studies recruited participants with BD younger than 18 years: the same group conducted a small observational study (n = 10) followed by a small RCT (n = 20) in which participants were randomized to DBT or “psychosocial treatment as usual” (psychotherapy primarily consisting of psychoeducational, supportive, and cognitive techniques) (Goldstein et al. 2007, 2015). In both studies, participants were recruited from a specialty mood disorders outpatient clinic and they were already receiving pharmacotherapy. Both studies used the same DBT intervention, which was adapted for the specific population (young, suicidal youths with BD) and alternating between individual therapy sessions and individual-family group skills training over 1 year; DBT team meetings were used in the RCT but not in the observation trial.

Both studies used validated scales measuring depressive symptoms, emotional dysregulation, manic symptoms, suicidality, and interpersonal functioning. The observational study found DBT to be both feasible and acceptable for the adolescent sample. While it also reported statistically significant improvements in depressive symptoms, emotion regulation, and suicidality, there was no significant improvement in manic symptoms, non-suicidal self-injury, or interpersonal functioning. The subsequent RCT confirmed that the intervention was feasible and acceptable, and showed a significantly larger improvement in depressive symptoms in the DBT group than in the control group. However, changes in emotional regulation or suicidality did not differ significantly between the two groups.

We reviewed eight publications reporting on nine studies that enrolled adult participants with BD: six RCTs and three observational studies. The first published adult study was a wait-list controlled RCT (n = 24) that assessed the feasibility and effectiveness of a DBT skills-based psychoeducational group “(Bipolar Disorders Group(BDG))” for adults with BD in a depressed or euthymic state (Dijk et al. 2013). The BDG consisted of 12 weekly 90-min sessions with eight sessions focused on DBT skills (distress tolerance, emotion regulations, and interpersonal effectiveness skills) and mindfulness skills taught throughout the 12-week intervention. There was only one dropout in each group and attendance and acceptability ratings were similarly high in both. Compared to the wait-list participants, BDG participants demonstrated a significant improvement in mindfulness skills assessed using a mindfulness self-efficacy scale. While they also experienced more improvement in depressive symptoms and in their ability to control emotional states, the difference between the two groups did not reach statistical significance. In the same publication, the authors also reported a significant improvement post-intervention on all symptom measures in a larger sample (n = 75) including their RCT participants and other patients who received the same BDG intervention (Dijk et al. 2013).

Another waitlist-controlled RCT (n = 60) investigated a psychoeducation-focused DBT group intervention based on the BDG of (Dijk et al. 2013, Afshari et al. 2019). Participants were hypomanic, depressed, or euthymic, and were receiving pharmacotherapy. The primary outcome measures selected a priori were executive functioning, mindfulness, and emotion regulation. The intervention group showed significantly more improvement than the control group on the three primary outcome measures and on measures of depression, mania, and emotion dysregulation.

Another RCT compared a 12-week DBT skills intervention and routine pharmacotherapy, with a primary focus on changes in executive functioning, in euthymic adult participants with BD I in maintenance phase (Zargar et al. 2019). While no significant changes were observed in executive functioning or depressive symptoms in either of the two groups, there were significantly higher improvements in manic symptoms and ability to control depressed mood states in the intervention group than in the control group.

A DBT-informed program adapted to target inter-episode mood instability in BD (Therapy for Inter-episode mood Variability in Bipolar (ThrIVe-B)) was assessed in an observational feasibility trial (n = 12) and an RCT (n = 43) (Wright et al. 2020; Wright et al. 2021). Both trials included adult participants with BD who had experienced several subthreshold hypomanic and depressive episodes over the preceding 2 years. Neither study standardized participants’ medications, and 67% and 88% of participants were receiving medications in the pilot and RCT samples, respectively. The 16-week ThrIVe-B program consisted of a combination of group meetings and individual therapy, structured in a modular format with skills-based content (mindfulness, emotion regulation, distress tolerance, and interpersonal effectiveness). The 2020 pilot study established the feasibility and acceptability of the program, based on the recruitment rate, intervention completion rate, and high satisfaction. In addition to its primary aim of confirming feasibility and acceptability, the follow-up RCT evaluated the usefulness of several measures under consideration for use in a future RCT. The RCT confirmed that the ThriVe-B program was feasible and acceptable overall. With respect to effectiveness, the improvements in sense of personal recovery and mindfulness were significantly higher in the intervention group than in the control group, but there were no significant differences between the two groups in the other measures including measures of depression, mania, affective lability, or quality of life.

An RCT compared treatment as usual (TAU), including medication management, with TAU augmented with psychoeducation and several DBT skills (mindfulness, interpersonal effectiveness skills, problem solving) in euthymic adult participants with BD (n = 65) (Valls et al. 2021). There was a significantly larger improvement in the DBT group than in the TAU group on the primary outcome measure, which assessed psychosocial functioning. The improvement in depressive symptoms was similarly significantly higher in the DBT group than in the TAU group; however, baseline depression ratings were low in both groups. There were no significant differences on other measures including mania, anxiety, episode relapse rates, cognition assessed with a 180-min neuropsychological battery, or quality of life.

One observational pilot study investigated a 12-week DBT skills group in euthymic participants with BD I (n = 37) (Eisner et al. 2017). All participants were already treated with pharmacotherapy and at least twice-a-month individual psychotherapy. The group intervention covered skills drawn directly from traditional DBT (mindfulness, emotion regulation, distress tolerance), with a particular focus on emotion regulation. The study demonstrated feasibility and acceptability of the skills group: with 25/37 (68%) participants completing therapy and 22/25 (88%) completers endorsing high satisfaction with the program. Participants also experienced significant improvement in mindfulness, distress tolerance, psychological well-being, post-intervention. There were no significant changes in depressive or manic symptoms; however, the sample had only mild depressive and manic symptoms at baseline.

Finally, an observation study of, a 9-week group-based psychotherapy designed to target emotion dysregulation in BD, has also been published (n = 16) (Painter et al. 2019). All participants had a diagnosis of BD-I and were euthymic, all but one was receiving medications. The program was adapted from an emotion-regulation intervention for patients with psychosis and it used key features of traditional DBT such as didactic training, home practice, and emphasis on DBT skills (emotion regulation, mindfulness, and reappraisal). Overall, the intervention was found to be feasible and acceptable, with 12/16 (75%) participants completing the intervention, 88.0% of sessions attended, and high rates of home practice and participant-rated helpfulness. Participants also demonstrated significant post-intervention improvement in measures associated with wellbeing, including mindfulness, emotion regulation, self-compassion, and affective experiences. There were no significant changes in depressive or manic symptoms.

The quality of the reviewed studies is reported in the Additional file 1: Table S1. All studies were evaluated as having a high risk of bias since they were at best single blinded with all participants aware they were receiving the intervention.