Of the individuals who came in to pick up their payment, 97% (N = 1884) also participated in giving saliva samples for DNA. We did not observe any differences between individuals who participated in the DNA component and those who did not in terms of sex (χ 2 = 0.23, p = 0.63); ethnicity of participants (χ 2 = 4.27, p = 0.12); or other major dimensions of substance use and related psychopathology [e.g., amount of alcohol drunk in the past month (t(1072) = −0.15, p = 0.89); FTND score (t(256) = −0.68, p = 0.21), symptoms of anxiety (t(1995) = 0.43, p = 0.66); symptoms of depression (t(1993) = 1.55, p = 0.12)].
