Depression in Alzheimer's disease: the effect of serotonin receptor gene variation.

This study investigated possible associations between selected polymorphisms in the serotonin receptor genes, 5-HT2A and 5-HT2C, with the presence of co-morbid depressive illness at baseline in a community based cohort of 158 patients with late onset patients with Alzheimer's disease (AD). An association was found between the presence of major depressive illness at baseline and both the 5-HT2A and 5-HT2C polymorphisms. Specifically, homozygous carriers of the 5-HT2A C102 allele were five times more likely to have major depressive illness than heterozygotes. In addition, homozygous or hemizygous carriers of the 5-HT2C Ser allele were 12 times more likely to have major depressive illness than homozygous or hemizygous carriers of the 5-HT2C Cys allele.