Correlates of Treatment Response in Depressed Older Adults With Bipolar Disorder

Aims: To identify baseline clinical factors associated with acute treatment response in depressed older adults with bipolar disorder (BD) receiving lamotrigine. Methods: Secondary analysis of a multisite, 12-week, open-label, uncontrolled study of add-on lamotrigine in 57 adults 60 years and older with BD I or II depression. Measures included the Montgomery Asberg Depression Rating Scale (MADRS) and Young Mania Rating Scale (YMRS). Cardiometabolic risk was measured with total serum cholesterol and the Cumulative Illness Rating Scale-Geriatric (CIRS-G) item # 13 (endocrine/metabolic burden). Neurocognitive (executive) function was evaluated using the Trail Making Test. Results: Greater reduction in MADRS from baseline was associated with higher baseline cardiometabolic burden at 6 and 9 weeks and lower YMRS scores at 9 weeks. At 12 weeks, improvement in the MADRS from baseline was no longer significantly related to baseline cardiometabolic burden or YMRS scores. A longitudinal mixed model of MADRS scores corroborated these findings with a significant finding of time-by-baseline cholesterol level interaction. In a subset of participants, better baseline executive function was related to greater improvement in the MADRS at 9 weeks but not at 6 or 12 weeks. Among all participants, higher baseline YMRS scores were related to greater likelihood of dropout. Conclusions: Lamotrigine appears to work best in depressed elderly patients with BD who have high cardiometabolic risk and low level of mania. Agents like lamotrigine that act primarily on neuroprogressive pathways involving oxidative stress, neurotrophins, and inflammation may be particularly effective in individuals with BD who have significant cardiometabolic burden because of their effects on shared vulnerability factors in BD and medical illness.