Serum lipid levels in seasonal affective disorder.

Previous research has assessed the relationship between blood lipid levels and depression with contradictory results. Several studies have linked low cholesterol levels with impulsive, aggressive and suicidal behaviours. The aim of this pilot study was to examine serum lipids in a sample of patients suffering from seasonal affective disorder (SAD). We conducted a retrospective analysis of data on total serum cholesterol and serum triglycerides in 39 SAD patients and 40 non-seasonally depressed or schizophrenic control subjects. Study subjects had to be free of psychotropic drugs for at least 2 weeks. Analysis of covariance (ANCOVA) was performed to assess group differences. After adjustment for significant covariates SAD patients had significantly lower total cholesterol levels (5.21 +/- 1.14 mmol/l) than control subjects (5.94 +/- 1.11 mmol/l; p = 0.013). Moreover, hypercholesterolemia (total cholesterol > 5.20 mmol/l) was significantly less frequent in the SAD group (46.2%) than in the control group (75.0%; p = 0.012). Total serum triglycerides did not differ significantly between SAD patients (1.54 +/- 1.07 mmol/l) and controls (1.56 +/- 0.96 mmol/l; p = 0.126). The results of this study support the idea that low cholesterol levels may be of pathogenetic importance in SAD. Further study in larger clinical samples is warranted to clarify our findings.