ROLE OF SEROTONIN TRANSPORTER PROMOTER REPEAT LENGTH POLYMORPHISM (5-HTTLPR) IN SEASONALITY AND SEASONAL AFFECTIVE-DISORDER

Seasonal variations in mood and behavior (seasonality) and seasonal af fective disorder (SAD) have been attributed to seasonal fluctuations i n brain serotonin (5-HT).(1) the short (s), as opposed to the long (l) , allele of the 5-HT transporter linked polymorphism (5-HTTLPR) has be en associated with neuroticism and depression.(2,3) We hypothesized th at this short allele would also be associated with SAD and with higher levels of seasonality. Ninety-seven SAD patients and 71 non-seasonal healthy controls with low seasonality levels were genotyped for 5-HTTL PR and compared statistically. Patients with SAD were less likely to h ave the l/l genotype (27.8% vs 47.9%; P < 0.01) and more likely to hav e the s allele (44.8% vs 32.4%; P < 0.02) as compared to controls. The three 5-HTTLPR genotypes were also differentially distributed in pati ents and controls (P < 0.03). The SAD patients with the l/l genotype h ad a lower mean seasonality score than did patients with the other two genotypes (mean +/- s.d. = 15.3+/-2.8 vs 17.1+/-3.4 respectively; P < 0.02). The 5-HTTLPR short allele contributes to the trait of seasonal ity and is a risk factor for SAD, providing further evidence for a rel ationship between genetic variation in the 5-HT transporter (5-HTT) an d behavior.