There is ample evidence of disturbed membrane phospholipid metabolism and oxidative stress in schizophrenia. Trials with fatty acid and antioxidant supplementation have shown conflicting results as regards symptoms. This study is part of a larger multicenter, double-blind, placebo-controlled trial of Ethyl-Eicosapentaenoic Acid (EPA) and antioxidants (vitamins E and C) as add-on to antipsychotic drugs in younger patients with schizophrenia and related disorders.
In the present study, we tested the effect of trial drugs on cognitive functioning in a geographically defined subgroup of these patients. Both patients (n=53) and controls (n=20) completed a broad battery of neuropsychological tests and were tested at baseline and at week 16. PUFA levels were measured in red blood cell (RBC) membranes. The longitudinal effects were analysed by Linear Mixed Model (SPSS 12.0). We expected the following hierarchy of effects, from greater to lower: 1) combined EPA and antioxidant treatment, 2) EPA or active antioxidants alone and 3) double placebo.
In contrast to our expectations, performance on CPT and Stroop was impaired in the groups receiving single supplements. Antioxidants prolonged the Stroop- conflict time and EPA impaired sustained attention, as measured by CPT dprime. These effects were restricted to the low-PUFA group, according to the bimodal distribution of PUFA levels found in the larger study. Combining EPA and antioxidants had a non-significant beneficial effect on sustained attention in the low-PUFA group only, compared to placebo. There were no other significant effects of trial drugs on neuropsychological measures.