FAAH gene variation associates with low human stress reactivity We next tested the influence of FAAH C385A on fear-related traits via personality testing in a population-representative birth cohort of young adults (N = 881).57 On the basis of our preclinical and imaging genetics findings, we focused our analysis specifically on Negative Emotionality as the salient superfactor within the Multidimensional Personality Questionnaire47 because this is a premorbid personality trait that predisposes individuals who are exposed to trauma to develop fear-related disorders.58 Cohort members carrying two copies of the lesser-expressing 385A variant scored significantly lower for Negative Emotionality (β = −0.08, t = 2.51, P<0.05). Negative Emotionality comprises three specific facets: Stress Reactivity, Aggression and Alienation. Specificity analyses revealed that, as predicted by the above findings, those homozygous for the lesser-expressing 385A variant were especially likely to exhibit low Stress Reactivity (β = −0.08, t = 239, P<0.05) (Figures 4c and d), but did not differ from other cohort members on Aggression (β = −0.04, t = 1.31, P>0.05) or Alienation (β = −0.05, t = 1.64, P>0.05). Thus, FAAH genetic variation
