Is Brain Derived Neurotrophic Factor (Bdnf) Associated With Smoking Initiation? Replication Using a Large Finnish Population Sample.

Introduction: Brain derived neurotrophic factor (BDNF) is a growth factor in the central nervous system. There is evidence for the involvement of BDNF in addictions and mental disorders. We aimed to replicate the earlier reported association of a functional genetic variant of BDNF with smoking initiation (SI) using a large population-based sample, and to test whether the association is independent of depression.

Methods: Our sample was drawn from the Finnish population-based FINRISK Surveys conducted in 1992, 1997, 2002 and 2007. We had non-missing data on the genotype BDNF Val66Met (G/A) variant (rs6265) and self-reported never (n=10,619) versus ever (n=16,028) smoking among 26,647 adults aged 25-74 years. The association between BDNF Val66Met and SI was modeled using logistic regression adjusted for age and sex, and in secondary analyses also for depression. Depression was defined as self-reported depression diagnosed or treated by physician during the past year.

Results: The sex and age adjusted analysis confirmed that the major (Val) allele increased the risk of being a lifetime ever smoker (per allele OR=1.07; 95%CI 1.01, 1.12; p=0.01). When depression, which itself was significantly associated with SI (OR=1.58; 95%CI 1.37, 1.82; p<0.001), was added to the model, the association of the gene with SI remained significant (per allele OR=1.06; 95%CI 1.01, 1.12; p=0.01). Exclusion of depressed individuals did not change the results (OR=1.06; 95%CI 1.01, 1.12; p=0.02).

Conclusions: In a Finnish population sample we replicated the earlier reported association of BDNF Val66Met with smoking initiation. Our data further suggest that this association is independent of depression.