Shape of change in internet based behavioral activation treatment for depression

•Examined shape of change, sudden gains and depression spikes in online treatment.•Quadratic shape of change best fit for online Behavioral Activation.•Sudden Gains but not depression spikes predicted more depression symptom reduction.•Client stressful life events and therapist concrete style related to sudden gains.•Therapy content finished but not amount of therapist contact related to sudden gain.

Shape of change, sudden gains and depression spikes were examined in an online 12-session Behavioral Activation (BA) treatment for depression. Client and therapist factors related to sudden gains were examined to investigate processes associated with outcome. Methods: Participants were postpartum Women with Major Depressive Disorder (n=42) who received online BA supported in 30-minute telephone sessions by a mental health worker. Depression symptoms were assessed at each session and number of sessions completed were recorded by the online program. Therapist records were rated for client stressful life event and therapist concrete focus. A quadratic pattern provided the best fit with the data; a cubic pattern was a poor fit. Sudden gains, but not depression spikes, predicted lower depression scores at 17-week outcome. Women who had higher baseline social functioning, did not experience a stressful life event during therapy, and completed more online modules, but not more telephone sessions, were more likely to have a sudden gain. A concrete therapist focus was associated with sudden gains. These results extend research on trajectories of change and sudden gains to an online BA treatment and to postpartum depression, and suggest important client and therapist factors associated with sudden gains.