Linear and Nonlinear Changes in Mood Between Psychotherapy Sessions: Implications for Treatment Outcome and Relapse Risk

Abstract

This study examined between-session changes in depressive mood among 91 older men and women receiving 16–20 sessions of outpatient psychotherapy. The majority of patients who recovered during treatment showed small between-session reductions in depression as measured by the Short Form Beck Depression Inventory. Still, nonlinearity in change was common, with most recovered patients experiencing two or more instances of major shifts toward mood worsening or improvement. The overall level of nonlinearity in change was positively correlated with recovery rate. Yet, high numbers of major mood shifts was linked with relapse risk. Patients who had relapsed at a 3-month follow-up experienced twice as many instances of major mood shifts during therapy as those who maintained their recovery.