Sleep, residual mood symptoms, and time to relapse in recovered patients with bipolar disorder.

Background: Sleep disturbance in bipolar disorder (BD) is common during and between mood episodes. In recovered (euthymic at least two months) BD patients, we assessed sleep compared to controls and its relationships with residual mood symptoms and mood episode recurrence.

Method: Recovered Stanford University BD Clinic patients diagnosed with the Systematic Treatment Enhancement Program for BD (STEP-BD) Affective Disorders Evaluation and monitored with the STEP-BD Clinical Monitoring Form (CMF) for >1 year and healthy controls completed the Pittsburgh Sleep Quality Index (PSQI). PSQI parameters were compared in BD patients versus controls, and the most robustly differentiating PSQI parameter was assessed in relationship to residual mood symptoms, and time to mood episode recurrence in BD patients.

Results: Eighty nine recovered BD patients compared to 56 healthy controls had significantly worse PSQI global score, more sleep medication use, longer sleep latency, and worse daytime dysfunction. PSQI global score had the greatest BD patient versus control effect size, and among BD patients, correlated significantly with residual mood symptoms and predicted earlier mood episode recurrence, even after covarying for residual mood symptoms.

Limitations: Use of subjective (PSQI) rather objective (polysomnography) sleep metric. Statistical power limited by small sample size. Potential psychotropic medication confound. Northern California tertiary BD clinic referral sample.

Conclusion: Further research is needed to confirm that in recovered BD patients, poor sleep quality correlates with residual mood symptoms, and independently predicts mood episode recurrence. If confirmed, these observations suggest potential mood benefit for focusing on sleep quality in interventions for recovered BD patients.