Genetic analysis supports ADHD as a causal risk factor for substance use disorders | Research

The takeaway

GWAS analysis confirmed shared genetic architecture between ADHD and substance use disorders, with evidence that genetic liability to ADHD causally increases SUD risk, while lifetime cannabis use genetically influenced ADHD risk.

Psychiatrists, addiction specialists, ADHD researchers, and genetic epidemiologists.

Genetic liability to ADHD causally increases substance use disorder risk

What the researchers found

The study confirmed a common genetic background between ADHD and SUD using both clinical (n=989) and population GWAS data. Mendelian randomization supported a causal effect of ADHD liability on SUD risk, and found a novel bidirectional effect where genetic liability for lifetime cannabis use influenced ADHD risk.

Why it matters

Understanding the genetic basis of ADHD-SUD comorbidity can improve screening and treatment approaches, particularly the novel finding that cannabis use liability may itself influence ADHD.

The numbers in context

Clinical sample: 989 subjects. Five SUD phenotypes tested: lifetime cannabis use, alcohol dependence, smoking initiation, cigarettes per day, and drinks per week. Shared genetic background confirmed for cannabis use, alcohol dependence, and smoking initiation.

How the study worked

Combined in-house clinical sample (989 ADHD subjects) with pre-existing GWAS datasets for five SUD-related phenotypes. Used polygenic risk score analysis, genetic correlation, and Mendelian randomization to assess shared genetics and causal relationships.

What this study cannot tell us

Cross-sectional genetic analysis cannot capture environmental interactions. Clinical sample was modest in size. Mendelian randomization assumptions may not fully hold.

How to read the evidence

Combines clinical and population genetic data with Mendelian randomization, though limited by sample size and cross-sectional design.

When this study was published

Published in 2021.

The bigger picture

Nearly one in four people with substance use disorders also has ADHD. These genetic findings support screening for ADHD in all SUD patients and monitoring substance use in ADHD patients.

Questions still open

How does the bidirectional genetic relationship between cannabis use and ADHD manifest clinically? Could early ADHD treatment reduce the genetic risk pathway to substance use disorders?

Common questions

Is the link between ADHD and substance use genetic?

Partially. This study found shared genetic variants between ADHD and multiple substance use phenotypes, including cannabis use, alcohol dependence, and smoking initiation.

Does cannabis use genetically influence ADHD?

The study found novel evidence that genetic liability for lifetime cannabis use was associated with ADHD risk, suggesting a bidirectional genetic relationship.

Read the original research

Genetic overlap and causality between substance use disorder and attention-deficit and hyperactivity disorder.

American journal of medical genetics. Part B, Neuropsychiatric genetics : the official publication of the International Society of Psychiatric Genetics, 186(3), 140-150

View on PubMed ↗Publisher’s paper ↗

Citation

Vilar-Ribó, Laura; Sánchez-Mora, Cristina; Rovira, Paula; Richarte, Vanesa; Corrales, Montserrat; Fadeuilhe, Christian; Arribas, Lorena; Casas, Miquel; Ramos-Quiroga, Josep Antoni; Ribasés, Marta; Soler Artigas, María. (2021). Genetic overlap and causality between substance use disorder and attention-deficit and hyperactivity disorder.. American journal of medical genetics. Part B, Neuropsychiatric genetics : the official publication of the International Society of Psychiatric Genetics, 186(3), 140-150. https://doi.org/10.1002/ajmg.b.32827