Gene DRD4 e o uso de substâncias em adultos com TDAH

Background: Most individuals with attention-deficit/hyperactivity disorder (ADHD) present one or more psychiatric comorbidities and substance use disorder (SUD) is one of the most frequent in adults. The dopaminergic system is related to the pathogenesis of externalizing disorders, which includes both ADHD and SUD. Thus, the aim of this study was to evaluate the effects of the 120 bp tandem duplication of the DRD4 gene in the susceptibility to ADHD in adults and to crack/cocaine addiction, as well as to evaluate the associated comorbidities in these two independent samples. Methods: The sample is composed by 555 adults with ADHD, 296 crack/cocaine addicts and 635 blood donors as control group. Association analysis for primary outcomes and comorbidities were performed using binary logistic regression. Results: Regarding susceptibility to ADHD and crack/cocaine addiction, we did not observe a significant association between the 120 bp duplication polymorphism and the disorders (p = 0.669, OR = 0.95; p = 0.559, OR = 1.167; respectively). However, evaluating the presence of comorbid SUD within the ADHD sample, it was observed that short allele carriers are at higher risk of developing SUD than homozygotes for the long allele (p = 0.023; OR = 1.679) and this effect was stronger for non-alcohol substance use (p = 0.010; OR = 2.085). Conclusion: Our results suggest that the short allele of the 120 bp tandem duplication of DRD4 gene influences the susceptibility to SUD when in simultaneous presence of ADHD