The socio-demographic and clinical characteristics of the participants are summarized in Table 1. The patient and control groups differed significantly in terms of sex and age. Most of the patients used cannabis and were cigarette smokers. Roughly half of the patients ingested more than 50 units of alcohol per week and had been in prison at least once. In terms of the preferred route of cocaine administration, 23% of the participants reported using the nasal route (snorting powder cocaine) exclusively, 9% reported using the inhalation route (smoking crack cocaine) exclusively, and 68% reported using both routes concurrently (dual users). For cases and controls, none of the allele distributions deviated significantly from those expected on the basis of the Hardy-Weinberg equilibrium (Table 2). When we adopted a recessive model of transmission, the GG genotype of rs4263329 was less common in cases than in controls [f(GG) = 1.2% vs. f(GG) = 2.6%; OR 2.3, 95% CI = 0.99–5.32]. After adjustment for age and sex, that association was no longer significant (P>0.1). As can be seen in Table 2, genotypes of the two
