Sudden gains and large intersession improvements in internet-based psychodynamic treatment (IPDT) for depressed adolescents.

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.