Serum concentrations of mood stabilizers are associated with memory, but not other cognitive domains in psychosis spectrum disorders; explorative analyses in a naturalistic setting

BACKGROUND: Mood stabilizers like lithium and anticonvulsants are used in bipolar and related psychotic disorders. There is a lack of knowledge of the relationship of these medications and cognition in the psychosis spectrum. We studied the association between serum concentration of mood stabilizers and cognitive performance in a well-characterized sample of bipolar and schizophrenia spectrum disorders. METHODS: Serum concentrations of valproate, lamotrigine, and lithium were analyzed for associations to performance on neuropsychological tests in six cognitive domains in individuals with bipolar disorder (n = 167) and in a combined sample of individuals with bipolar or schizophrenia spectrum disorders (n = 217). Linear regression with adjustments for gender, age, and symptom levels of depression, mania, and psychosis were applied for the association analyses. RESULTS: There were negative associations between serum levels of valproate and short term delayed recall (bipolar: p = 0.043; combined: p = 0.044) and working memory (bipolar: p = 0.043). A positive association was suggested between serum level of lithium and working memory (bipolar: p = 0.039). There were no other significant relationships between serum levels of valproate, lamotrigine, or lithium and neuropsychological test performance in neither the bipolar disorder nor the combined group. CONCLUSIONS: Serum levels of mood stabilizers were unrelated to cognitive performance in most domains, indicating that higher dose does not lead to broader cognitive impairments in bipolar and related psychotic disorder patients. However, worsened memory with increasing levels of valproate suggests cautious dosing of anticonvulsants, while increasing lithium level seems to be associated with improved memory. The findings should be interpreted with caution due to the explorative, naturalistic design.