Participants were drawn from the June 2014 public data release from the HCP (N=527), which aims to recruit 1,200 individuals (3-4 siblings per family, most including a twin pair)14. All participants were 22-35 years old; for all inclusion/exclusion criteria, see14. Participants were not excluded for recreational drug use (unless they reported being hospitalized for ≥2 days for substance abuse or being treated by a medical specialist for ≥12 months for substance abuse [or any psychiatric or neurological condition]).
