Anxiety disorders peak in incidence during adolescence, but many treatments are based on studies in adults. Understanding how genetic factors influence the risk of developing psychiatric disorders at different stages of brain development is critical for optimizing treatments.

To address this question, researchers. studied how a common genetic variant that affects endocannabinoid signaling alters the development of frontolimbic circuitry, possibly contributing to the emergence of anxiety-related behavior during adolescence. The authors used diffusion MRI to measure the connectivity between prefrontal cortex and limbic structures in 1,050 individuals 3–21 years of age.

Some participants had higher levels of endocannabinoids due to a genetic variant that interferes with the activity of the fatty acid amide hydrolase (FAAH) enzyme, which breaks down endocannabinoids. Compared with individuals without the FAAH variant allele, those with the allele displayed higher frontolimbic connectivity and lower self-reported anxiety, but only after 12 years of age.

The findings demonstrate that the effect of this genetic factor on brain circuitry and anxiety-related behavior emerges during adolescence. According to the authors, the results might aid the development of biomarkers for anxiety, as well as precision medicine approaches that optimize the treatment of adolescents with psychiatric disorders. 

http://www.pnas.org/content/early/2016/03/16/1600013113