People with attention deficit hyperactivity disorder (ADHD) have a genetic predisposition to the use -and abuse- of cannabis. This was confirmed by an international study led by the Vall d'Hebron hospital in Barcelona after analyzing the genome of more than 85,000 people. The researchers concluded that people with this neurodevelopmental condition multiply by eight the risk of consuming cannabis throughout life. The study found four shared genetic regions between ADHD and consumption of this substance.
The experience in the consultation already indicated where the shots were going, but a rigorous scientific study was lacking that verified what the psychiatrists had been visiting for a long time. "We saw that patients with ADHD consumed more cannabis than the general population, 40% were addicted to cannabis, and in the general population about 13%, what we did not know was what factors involved this high risk", explains Dr. Josep Antoni Ramos Quiroga, Head of Psychiatry Vall d'Hebron. ADHD affects 5% of the population in childhood and remains in half of adult patients. It is characterized by lack of attention, disorganization, impulsivity and hyperactivity, and implies low academic performance, difficulty in social relationships and drug abuse, among other behavioral problems.
Based on the premise - validated by other scientific studies - that 75% of ADHD and about 40% of cannabis use have a genetic explanation, researchers analyzed the genome of some 85,000 people to find shared genetic variants and causality , from mathematical and statistical studies, between the mental disorder and the consumption of this substance. "There is a certain genetic overlap, around 30%, between ADHD and cannabis use, they are genetic variants, simple nucleotide changes, which confer a higher risk, a predisposition," explains Dr. Marta Ribasés, principal investigator of the group. of Psychiatry, Mental Health and Addictions of the Vall d'Hebron Institute of Research (VHIR).
The changes found occur in genes that are related to the formation of neurons. "We are talking about many genetic variables in different areas that participate in the formation of the brain, modulate the brain and make them more vulnerable," explains Ramos Quiroga. The psychiatrist does not know, however, the depth of these changes. "We have to see if these genetic differences involve changes in brain structure," he admits.
In any case, this study, which has been published in the scientific journal Molecular Psychiatry, opens the door to modify clinical practice to reinforce prevention in drug addiction. "Patients with ADHD have more prevalence of consumption and start earlier, at age 12. We can not do prevention at 14 or 15. It does not make sense, you have to start at nine," says Ramos Quiroga. In addition, the researchers insist, this study will also serve to improve early detection and help families understand why their children with ADHD use cannabis.
Cannabis and schizophrenia
This is not the first time that the genetic links between a mental disorder and the predisposition to cannabis use have been confirmed. Precisely, Vall d'Hebron participated in another international study with 184,765 patients that revealed that the 24% of the genetic base that predisposes to consuming cannabis is shared with the genetic basis of schizophrenia.
Likewise, the genetic bonds also cross each other between the mental disorders themselves. In the framework of an international consortium, hundreds of scientists from around the world analyzed the genetic basis of 25 brain disorders (psychiatric and neurological) from the study of the genome of 215,683 patients and 657,164 control individuals. The result was, among other conclusions, that schizophrenia, bipolar disorder, major depression and ADHD, share between them around 40% of common genetic base.
"There is that article from the international consortium and now we are trying to relate to addictions, we try to validate our hypotheses, what functions these genes have beyond those that are described, in genetic predictions to personalize the treatments ...", says Ramos Quiroga . The hospital is also immersed in a study with 3,000 patients at the center to explore the genetic relationship between ADHD and other drugs, such as cocaine.