Memory performance predicts response to psychotherapy for depression in bipolar disorder: A pilot randomized controlled trial with exploratory functional magnetic resonance imaging.

Objective: This pilot randomized controlled trial compared Cognitive Behavior Therapy (CBT) and Supportive Psychotherapy (SP) for the treatment of depression in bipolar I disorder. We also examined whether exploratory verbal memory, executive functioning, and neural correlates of verbal memory during functional magnetic resonance imaging (fMRI) predicted change in depression severity.

Methods: Thirty-two adults (ages 18-65) with DSM-IV bipolar I disorder meeting current criteria for a major depressive episode were randomized to 18 weeks of CBT or SP. Symptom severity was assessed before, at the mid-point, and after the 18-week intervention. All participants completed a brief pre-treatment neuropsychological testing battery (including the California Verbal Learning Test-2nd Edition, Delis Kaplan Executive Functioning System [DKEFS] Trail-making Test, and DKEFS Sorting Test), and a sub-set of 17 participants provided usable fMRI data while completing a verbal learning paradigm that consisted of encoding word lists.

Results: CBT and SP yielded comparable improvement in depressive symptoms from pre- to post-treatment. Better retention of learned information (CVLT-II long delay free recall vs. Trial 5) and recognition (CVLT-II hits) were associated with greater improvement in depression in both treatments. Increased activation in the left dorsolateral prefrontal cortex and right hippocampus during encoding was also related to depressive symptom improvement.

Limitations: Sample size precluded tests of clinical factors that may interact with cognitive/neural function to predict treatment outcome.

Conclusion: Neuropsychological assessment and fMRI offer additive information regarding who is most likely to benefit from psychotherapy for bipolar depression.