Social support in older individuals: the role of the BDNF Val66Met polymorphism.

Although often viewed as a purely environmental construct, perception of social support may be influenced by genetic factors. This study examined the relationship between the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism and social support measures in older subjects. The sample consisted of 243 depressed and 115 nondepressed older subjects, age 60 years or older; 233 were Val66 allele homozygotes, while 125 were Met66 allele carriers. All subjects completed clinical assessments, including a self-report questionnaire assessing four social support domains, and provided blood for genotyping. Statistical models examined the relationship between scale scores of social support and BDNF Val66Met genotype, while controlling for presence or absence of major depressive disorder and other demographic factors significantly associated with social support. As social support measures were not normally distributed, log-transformed scores were examined. After controlling for diagnosis and education level, the Met66 allele was associated with lower levels of subjective social support (F(1,357) = 5.33, P = 0.0216) and a trend for fewer social interactions (F(1,357) = 3.66, P = 0.0567). To our knowledge, this is the first report associating a measure of social support with a genetic polymorphism. This supports previous work that genetic factors may influence social support perception. Further work is needed to determine the generalizability of this finding to the broader population, as well as its significance for clinical outcomes.