BDNF val66met genotype shows distinct associations with the acoustic startle reflex and the cortisol stress response in young adults and children

•We examined the effect of BDNF val66met on peripheral physiological markers.•Startle reflex and cortisol stress response were investigated.•Three adult samples and one children sample were analysed.•Met allele carriers had enhanced cortisol responses but smaller startle magnitudes.

Brain Derived Neurotrophic Factor (BDNF) is a crucial regulator of neuronal development, organization and function and the val66met polymorphism in the BDNF gene has been associated with several (endo-) phenotypes of cognitive and affective processing. The BDNF met allele is considered a risk factor for anxiety and fear related phenotypes although findings are not entirely consistent. Here, the impact of BDNF val66met on two parameters of anxiety and stress was investigated in a series of studies. Acoustic startle responses were assessed in three adult samples (N1 = 117, N2 = 104, N3 = 116) as well as a children sample (N4 = 123). Cortisol increase in response to the Trier Social Stress Test (TSST) was measured in one adult sample (N3) and in the children sample (N4). The BDNF met allele was associated with enhanced cortisol responses in young adults (p = 0.039) and children (p = 0.013). On the contrary, BDNF met allele carriers showed a reduced acoustic startle response which reached significance in most samples (N1: p = 0.004; N2: p = 0.045; N3: n.s., N4: p = 0.043) pointing to differential effects of BDNF val66met on distinct endophenotypes of anxiety and stress-related responses. However, small effect sizes suggest substantial additional genetic as well as environmental contributors.