Differential response of positive valence systems to psychotherapy for late-life depression: A pilot study.

Background: Depression is characterized by deficits in the positive valence systems (PVS), which also decline with age. However, few studies have examined changes in PVS as a mechanism of treatment for depression, and none have done so using reward-focused interventions in older adults.

Aim: The aim of this proof-of-concept study was to investigate changes in two event-related potential measures of PVS function, the late positive potential and the reward positivity, during psychotherapy designed to treat late-life depression by increasing rewarding experiences.

Methods: Eighteen adults age ≥ 60 with major depressive disorder recruited for a larger randomized controlled trial received 9 weeks of Problem-Solving Therapy or Engage therapy. The late positive potential and the reward positivity were recorded at baseline and week 6 of treatment.

Results: The late positive potential was larger for rewarding compared to neutral stimuli and increased from baseline to week 6. Exploratory analyses found that this increase was specific to rewarding stimuli. There were no significant effects for the reward positivity.

Limitations: The small sample size limited power to detect associations with clinical measures or evaluate moderating effects of treatment modality, age, or gender.

Conclusions: This study provides preliminary evidence that distinct facets of the PVS respond differently to psychotherapy in older adults with major depression. The late positive potential may be a dynamic marker of depressive state, whereas the reward positivity may constitute a vulnerability index for late-life depression.