Variability in the 5-MT2A receptor gene is associated with seasonal pattern in major depression

The 102-T/C polymorphism of the 5-HT2A receptor gene was analysed in 159 pa tients with major depression and 164 unrelated and healthy controls using a case-control design. Allele and genotype frequencies did not differ betwee n cases and controls. No differences according to sex, age of onset, melanc holia, suicidal behaviour or family history of psychiatric illness were fou nd. However, genotype distributions significantly differed between patients with seasonal pattern in their episodes (MDS) and patients with no seasona l pattern (N-MDS) (chi (2) = 10.63; P = 0.004). A seasonal pattern was 7.57 times more frequent in 102C-allele carriers than in 102T homozygous (95.1% of patients MDS carried 102C-allele vs 72% of patients N-MDS (chi (2) = 9. 45, df=1, P = 0.002; OR = 7.57 (95% Cl: 1.65-48.08)). These results suggest that variation in the 5-HT2A receptor gene may play a role in the developm ent of major depression with seasonal pattern and support the existence of a genetic and etiological heterogeneity underlying the diagnosis of major d epression.