Relationship Between Attention Deficit Hyperactivity Disorder and Alcohol Dependence: A Genetic View

Abstract

Implication for health policy/practice/research/medical education: ADHD is highly comorbid with alcohol dependence. It is essential to understand the pathogenesis of these comorbity psychiatric disorders. This article emphasizes on the biological mechanism of the relationship between ADHD and alcohol and drug dependence. This study has implication for researchers and psychiatric educators. Attention deficit hyperactivity disorder (ADHD), is a common, highly heritable childhood-onset psychiatric disorder affecting 2%-6% of children worldwide. The recent paper examines the effects of child and adult ADHD symptoms in adults among male students on adult addiction acknowledgment and alcoholism potential (1). This article is an original study which provides that adult ADHD and child ADHD predict addiction acknowledgment while child ADHD and impulsivity predict alcohol potential. These findings add new evidence about prediction of adolescent and adult drug abuse and use by early ADHD. However, the biological mechanism of the relationship between ADHD and substance problems is still unclear. One of the important mechanisms is genetic correlation due to shared genetic loci. First, it has been shown that both ADHD and alcohol dependence have strong genetics components. Twin and adoption studies have indicated that ADHD has high heritability in the range of 75%-91% (2), while family, twin, and adoption studies have revealed that genetic and environmental factors and their interactions contribute to the development of alcohol dependence, with a heritability of more than 50% (3). Second, ADHD has been found to be highly comorbid with nicotine dependence and alcohol dependence. Segregation analysis has provided multi-generational evidence of cosegregation among ADHD, nicotine dependence, and alcohol dependence, while linkage analysis has suggested several regions on human chromosomes with pleiotropic effects on ADHD and alcohol dependence (4). For example, significant linkages at 4q13.1-13.2 and 5q31-33 for ADHD has been implicated in alcohol dependence and nicotine dependence (4). Third, genetic association studies have suggested several genes which are responsible for both ADHD and alcohol dependence. For example, it has been reported associations between the dopamine transporter (DAT) gene polymor-phisms and human disorders including ADHD and alcohol dependence (5). The variants of the dopamine D2 re