Gene-environment interactions in attention-deficit/hyperactivity disorder

Abstract

Attention-deficit/hyperactivity disorder (ADHD) is a heterogeneous disorder characterized by inattention, impulsivity, and/or hyperactivity in children and adults. Putative environmental risk factors for ADHD include toxin and prenatal smoke exposure, low socioeconomic status, and parental marital instability and discord. Genetic associations with ADHD have been found in the dopaminergic, serotonergic, and noradrenergic neurotransmitter systems, but findings are inconsistent across studies. Herein, we review studies of gene-environment interactions for ADHD to better understand how genetic and environmental risk factors may contribute to the disorder in a nonindependent fashion, which may account in part for the inconsistent findings on genetic associations. Although evidence of interactions between prenatal substance exposure and the dopamine genes DAT1 and DRD4 was found, findings across studies have been mixed. We discuss these findings and the future directions and limitations of current gene-environment research.

How French media have portrayed ADHD to the lay public and to social workers

“…In contrast, five articles, in agreement with the present scientific consensus (Ficks & Waldman, 2009; Li et al, 2014; Sonuga-Barke, 2010), challenged this claim. For example we found in Le Figaro (19 February 2004): “It is obvious that hyperactive children suffering from attention deficit are increasingly numerous.…”

“…We tested whether and how they reported on three scientific questions about ADHD: (i) whether ADHD is mainly genetic in origin; (ii) whether methylphenidate treatment decreases the risk of academic underachievement; and (iii) whether brain imaging techniques are able to reveal ADHD in individual patients. Scientific studies demonstrated that genetic factors only mildly contribute to ADHD etiology whereas environmental factors play a central role (Ficks & Waldman, 2009; Sonuga-Barke, 2010). In a recent review of more than 300 molecular genetic studies (Li, Chang, Zhang, Gao, & Wang, 2014, p. 19), the authors concluded: “current findings from genetic studies of ADHD are still inconsistent and inconclusive.…”

Genetic Risks and ADHD Symptomatology: Exploring the Effects of Parental Antisocial Behaviors in an Adoption-Based Study

“…These treatment modalities have flowed, in part, from research examining the etiology of ADHD and ADHD symptomatologies. Most of the extant research has indicated that ADHD is a complex multifactorial phenotype that is influenced in large part by genetic factors and even gene-environment interactions [5,7,14,[32][33][34][35][36][37][38][39][40]. The current study added to the existing body of research by examining whether genetic liabilities for criminality and alcoholism affected ADHD symptoms in a sample of American adoptees.…”

“…As a result, it was not possible to separate the effects of having an alcoholic or criminal biological parent from the effects of having an ADHD biological parent. Third, there is some evidence that exposure to toxins either in utero or very early in life may be related to the development of ADHD [32,34,37,41]. Given that parents with ADHD and criminal parents are at risk for financial problems and living in disadvantaged environments [42][43][44][45], it is possible that the connection between genetic risk and ADHD is mediated through disadvantaged environments.…”

Why does ADHD Confer Risk for Cigarette Smoking? A Review of Psychosocial Mechanisms

“…For instance, it may be that the problems with the dopaminergic system that are related to ADHD and smoking are also linked to some of the cognitive deficits (e.g., cognitive coping) or social factors (e.g., parental smoking) which are associated with ADHD and smoking. Studies on gene-environment interactions and general ADHD symptomology suggest that there may be interactions between these dopaminergic genes and prenatal risk factors (e.g., maternal smoking during pregnancy) which increase a child's risk for ADHD (Ficks and Waldman 2009;Plomp et al 2009). While the literature on gene-environment interactions and ADHD is just emerging as an important area of research, similar studies could examine these interactions related to cigarette smoking and ADHD.…”