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Institute
Interindividual variability in the regulation of the human stress system accounts for a part of the individual's liability to stress-related diseases. These differences are influenced by environmental and genetic factors. Early childhood adversity is a well-studied environmental factor affecting an individual's stress response which has been shown to be modulated by gene environment interaction (GxE). Neuropeptide Y (NPY) plays a role in stress regulation and genetic variation in NPY may influence stress responses. In this study, we analyzed the association of a common variant in the NPY gene promoter, rs16147, with cortisol and ACTH responses to acute psychosocial stress in young adults from the Mannheim Study of Children at Risk (MARS), an ongoing epidemiological cohort study following the outcome of early adversity from birth into adulthood. We found evidence of a GxE interaction between rs16147 and early adversity significantly affecting HPA axis responses to acute psychosocial stress. These findings suggest that the neurobiological mechanisms linking early adverse experience and later neuroendocrine stress regulation are modulated by a gene variant whose functional relevance is documented by increasing convergent evidence from in vitro, animal and human studies.
Evidence from animal research has revealed that less maternal care results in disturbed emotionality in the offspring. In the present study, the long-term impact of maternal responsiveness and stimulation during early mother child interaction on depressive psychopathology was examined until adulthood. Data are from an epidemiological cohort study of the long-term outcome of early risk factors assessed at birth. At age 3 months, mothers and infants were videotaped during a nursing and playing situation. Maternal responsiveness and stimulation as well as infant responsiveness were evaluated by trained raters. At age 19 years, 314 participants (145 males, 169 females) were characterized on measures of depression through interview and questionnaire. In addition, measures of depression and anxiety were available from assessments in childhood. Results indicated that less maternal stimulation during early interaction was associated with a higher risk of depression in the offspring until the age of 19 years. In addition, children of less stimulating mothers showed more depressive symptoms at age 19 years and displayed more anxiety and depressive symptoms between the ages of 4.5 and 15 years. In contrast, maternal responsiveness was unrelated to children's outcome. In accordance with findings from animal research, the present study provides first longitudinal evidence in humans of a continuous and long-term influence of early maternal interaction behavior on the offspring's psychological adjustment until adulthood. The results suggest that the amount of maternally initiated contact behavior in a very early developmental stage may be crucial for children's mental health, regardless of child and maternal responsiveness.
Alcohol abuse and dependence have proven to be complex genetic traits that are influenced by environmental factors. Primate and human studies have shown that early life stress increases the propensity for alcohol abuse in later life. The reinforcing properties of alcohol are mediated by dopaminergic signaling; however, there is little evidence to indicate how stress alters alcohol reinforcement. KCNJ6 (the gene encoding G-protein-coupled inwardly rectifying potassium channel 2 (GIRK2)) is a brain expressed potassium channel with inhibitory effects on dopaminergic tone. The properties of GIRK2 have been shown to be enhanced by the stress peptide corticotrophin-releasing hormone. Therefore, we sought to examine the role of KCNJ6 polymorphisms in adult alcohol dependence and stress-related alcohol abuse in adolescents. We selected 11 SNPs in the promoter region of KCNJ6, which were genotyped in 1152 adult alcohol dependents and 1203 controls. One SNP, rs2836016, was found to be associated with alcohol dependence (p = 0.01, false discovery rate). We then assessed rs2836016 in an adolescent sample of 261 subjects, which were characterized for early life stress and adolescent hazardous drinking, defined using the Alcohol Use Disorders Identification Test (AUDIT), to examine gene-environment interactions. In the adolescent sample, the risk genotype of rs2836016 was significantly associated with increased AUDIT scores, but only in those individuals exposed to high levels of psychosocial stress in early life (p = 0.01). Our findings show that KCNJ6 is associated with alcohol dependence and may moderate the effect of early psychosocial stress on risky alcohol drinking in adolescents. We have identified a candidate gene for future studies investigating a possible functional link between the response to stress and alcohol reinforcement.