Abstract
The present study tested outcomes of the Transdiagnostic Sleep and Circadian Intervention (TranS-C) among midlife and older adults with serious mental illness (SMI). Further, we tested predictors-credibility, expectancy, usefulness, and utilization-that may affect TranS-C outcomes. Midlife and older participants from a community setting (>49 years, 62.3% female, 37.7% African American or Black) with sleep and circadian problems and SMI were randomized to receive TranS-C plus usual care (TranS-C+UC, n = 27) or usual care followed by delayed treatment with TranS-C (UC-DT, n = 26). Immediate and delayed TranS-C data were combined to increase power (combined n = 52). Outcomes were assessed at pretreatment, posttreatment, and 6-month follow-up. Credibility and expectancy were assessed during the second session. Usefulness and utilization of TranS-C skills were assessed at posttreatment and 6-month follow-up. TranS-C+UC, relative to UC-DT, was associated with improvements in depression symptoms, sleep disturbance, overall sleep health, and select sleep/wake outcomes, though not all improvements were sustained at 6-month follow-up. Lower usefulness of TranS-C skills predicted more severe sleep disturbance at posttreatment and daytime sleep-related impairment at posttreatment and 6-month follow-up. Lower utilization predicted more severe psychiatric symptoms at posttreatment, sleep disturbance at posttreatment and 6-month follow-up, and overall impairment and daytime sleep-related impairment at 6-month follow-up. Higher credibility and expectancy predicted greater usefulness of TranS-C skills at posttreatment and 6-month follow-up and greater utilization at 6-month follow-up. Together, findings highlight benefits of TranS-C for midlife and older adults with SMI. However, boosting credibility, expectancy, utilization, and usefulness may meaningfully improve TranS-C outcomes.