Cognitive outcomes are differentially associated with depression severity trajectories during psychotherapy treatment for late life major depressive disorder.

Objectives: Late Life Depression (LLD) is associated with persistent cognitive dysfunction even after depression symptoms improve. The present study was designed to examine cognitive outcomes associated with the pattern of depression severity change during psychotherapy intervention for LLD.

Methods: 96 community-dwelling adults ages 65-91 with major depressive disorder completed 12 sessions of Problem-Solving Therapy at the University of California, San Francisco. Nonlinear trajectories of depression severity ratings using the Hamilton Depression Rating Scale were computed from multiple time points collected throughout the weekly psychotherapy intervention. Performance on measures of cognition (information processing speed, executive functioning, verbal learning, memory) was assessed at baseline and post-treatment. Linear mixed-effects models examined associations between nonlinear depression severity trajectories and post-treatment change in cognitive performance.

Results: Broadly, different patterns of depression change during treatment were associated with improved cognition post-treatment. Greater and more consistent interval improvements in depression ratings were differentially associated with improvements in aspects of verbal learning, memory, and executive function post-treatment, while no associations were found with information processing speed.

Conclusions: The heterogeneity of depression trajectories associated with improved cognitive outcomes suggests that the temporal pattern of depression response may impact specific cognitive processes distinctly. Results suggest that use of nonlinear depression severity trajectories may help to elucidate complex associations between the time course of depression response and cognitive outcomes of psychotherapy in LLD. These findings have important implications for identifying treatment targets to enhance clinical and cognitive outcomes of psychotherapy in LLD.