Some variations in the gene LPHN3, which is associated with attention-deficit/ hyperactivity disorder (ADHD) in adults and children, are linked to addictive alcohol or substance abuse. The study published in Translational Psychiatry shows how genetic variation could favor the likelihood of smoking, consuming alcohol, cannabis and other addictive substances.
The findings are based on the study of around 2,700 patients -children, adolescents and adults- from the United States, Colombia and Spain, and it will contribute to provide new genetic tools to improve prevention of addictive behaviors in people with ADHD.
ADHD: a complex disorder affecting children, adolescents and adults
The connection between LPHN3 and ADHD is one of the most studied regarding the etiology of the disorder. This gene, in addition, has an impact on the patients' response to the medication, the degree of severity of the disease and disruptive behavior. However, so far, the depth of the relation between the gene LPHN3 and substance addiction had not been explored.
In the new study, the experts applied an innovative statistical method (Recursive-partitioning Frameworks) which integrates clinical, demographic and genetic information on a specific disorder -in this case, ADHD- to predict another co-morbid disorder (which appears concurringly), such as addiction to tobacco, alcohol, cocaine, cannabis and marijuana, among others.
Conclusions note that, within the group of Spanish patients with ADHD, a specific variation of the LPHN3 gene increases by 40 % the risk of nicotine dependence. According to the experts, results are similar in the cases for alcohol and illegal drugs, which have been studied together in the research.
Why some patients use addictive substances and others do not?
Not all those affected by ADHD show behaviors with an addictive profile over their lives. "We now know genetics play an important role in these behaviors. This helps us to prevent future risks in kids and adults with ADHD and to improve prevention strategies. However, ADHD genetics are diverse, there are many involved genes and these vary among the patients with the disorder", notes Cormand.
75 % of ADHD has a genetic base and the remaining 25 % is related to environmental factors which can vary, according to the experts. Therefore, external factors can be relevant in the appearance of addictive behaviors in people with ADHD. For example, certain lifestyles or social interactions can play an important role.
"Also, cocaine and other addictive substances -warns Cormand- have a psychostimulant action similar to the one in the main pharmacological treatment for ADHD. This would explain why, in some cases, these are used by the affected people as self-medication for its apparently 'beneficial' effects".
Addictive behaviors: clinical studies to improve prevention measures
Psychological and pharmacological treatment and psychopedagogical intervention are the combined strategies that are most efficient in ADHD treatment. In the future, we will need new clinical studies to analyze the importance of genetics in ADHD susceptibility and addictive behaviors which can affect the patient's health.
"It is difficult to access patients with an ADHD diagnosis and records of drug use who authorize participation in these research studies. Also, in genetic studies, population samples have to be homogeneous. Other added problems are the difficulty to get data from all individuals, or even from those who can lie about their use of addictive substances", concludes the researcher Nočlia Fernāndez, from the Department of Genetics, Microbiology and Statistics of the UB, and member of IBUB, CIBERER and IRSJD.