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

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. 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. A total of 17 patients (25.75%) experienced an SG. The effect of having an SG or early SG was non-significant after treatment ( = 0.48) and at follow-up ( = 0.66). However, having an LII was related to better outcome after treatment (= 0.97) and at follow-up ( =0.76). Early LIIs were associated with significantly better results at end of treatment ( = 0.72). 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.