Background: Adolescent major depressive disorder (MDD) is highly prevalent and associated with lifelong adversity. Evidence-based treatments exist, but accessible treatment alternatives are needed. We aimed to compare internet-based psychodynamictherapy (IPDT) with an established evidence-based treatment (internet-based cognitive behavioural therapy [ICBT]) for the treatment of adolescents with depression.

Methods: In this randomised, clinical trial, we tested whether IPDT was non-inferior to ICBT in the treatment of adolescent MDD. Eligible participants were 15–19 years old, presenting with a primary diagnosis of MDD according to DSM-5. Participants were recruited nationwide in Sweden through advertisements on social media, as well as contacts with junior and senior high schools, youth associations, social workers, and health-care providers. Adolescents who scored 9 or higher on the Quick Inventory of Depressive Symptomatology for Adolescents (QIDS-A17-SR) in an initial online screening were contacted by telephone for a diagnostic assessment using the Mini International Neuropsychiatric Interview. Participants were randomly assigned to ICBT or IPDT. Both interventions comprised eight self-help modules delivered over 10 weeks on a secure online platform. The primary outcome was change in depression severity measured weekly by the QIDS-A17-SR. Primary analyses were based on an intention-to-treat sample including all participants randomly assigned. A non-inferiority margin of Cohen's d=0·30 was predefined. The study is registered at ISRCTN, ISRCTN12552584.

Findings: Between Aug 19, 2019, and Oct 7, 2020, 996 young people completed screening; 516 (52%) were contacted for a diagnostic interview. 272 participants were eligible and randomly assigned to ICBT (n=136) or IPDT (n=136). In the ICBT group, 51 (38%) of 136 participants were classified as remitted, and 54 (40%) of 136 participants were classified as remitted in the IPDT group. Within-group effects were large (ICBT: within-group d=1·75, 95% CI 1·49 to 2·01; IPDT: within-group d=1·93, 1·67 to 2·20; both p<0·0001). No statistically significant treatment difference was found in the intention-to-treat analysis. Non-inferiority for IPDT was shown for the estimated change in depression during treatment (d=–0·18, 90% CI –0·49 to 0·13; p=0·34). All secondary outcomes showed non-significant between-group differences.

Interpretation: IPDT was non-inferior to ICBT in terms of change in depression for the treatment of adolescents with MDD. This finding increases the range of accessible and effective treatment alternatives for adolescents with depression.

Objective: Although psychodynamic psychotherapy is efficacious in the treatment of depression, research on mechanisms of change is still scarce. The aim of this study was to investigate if and how emotion regulation affects outcome both as a time-invariant and a lagged time-varying predictor.

Method: The sample consisted of 67 adolescents diagnosed with major depressive disorder, attending affect-focused psychodynamic internet-based treatment (IPDT). Linear mixed models were used to analyze emotion regulation as a baseline predictor and to assess the effect of within-person changes in emotion regulation on depression.

Results: Analyses suggested that emotion regulation at baseline was a significant predictor of outcome, where participants with relatively larger emotion regulation deficits gained more from IPDT. Further, the results showed a significant effect of improved emotion regulation on subsequent depressive symptomatology. When not controlling for time, increased emotion regulation explained 41.23% of the variance in subsequent symptoms of depression. When detrending the results were still significant, but the amount of explained variance was reduced to 8.7%.

Conclusion: The findings suggest that patients with relatively larger deficits in emotion regulation gain more from IPDT. Decreased emotion regulation deficits seem to act as a mechanism of change in IPDT as it drives subsequent changes in depression.

International Standard Randomised Controlled Trial Number (ISRCTN) 16206254, https://doi.org/10.1186/ISRCTN16206254.

Objective: Sudden gains (SGs) have often been found associated with better treatment outcome across different psychiatric disorders. However, no studies have evaluated SGs in internet-based treatment targeting adolescent depression. Method: The sample consisted of 66 adolescents diagnosed with major depressive disorder, attending psychodynamic internet-based treatment. Effects of SGs were evaluated at posttreatment and 6-month follow-up. We also evaluated effects of large intersession improvements (LIIs; sudden and relatively large gains, between sessions, without the stability criterion). Effects of SGs and LIIs early in treatment were also investigated. Results: A total of 17 patients (25.75%) experienced an SG. The effect of having an SG or early SG was non-significant after treatment (d = 0.48) and at follow-up (d= 0.66). However, having an LII was related to better outcome after treatment (d = 0.97) and at follow-up (d = 0.76). Early LIIs were associated with significantly better results at end of treatment (d = 0.72).Conclusions: The original criteria of SGs might be overly conservative and thus miss important improvements in depression. Relatively large intersession gains, regardless of stability, seem to be predictive of outcome.