Young people who are genetically vulnerable to depression should be extra careful about smoking marijuana: A new study out of the Netherlands suggests cannabis use can lead to increased risk of developing depressive symptoms.
According to researcher Roy Otten at the Behavioural Science Institute of Radboud University Nijmegen, two-thirds of the population have the gene variant that makes one sensitive to depression.
Many young people use cannabis in the Netherlands, where adult residents can legally smoke cannabis in “coffee shops.” Nearly 30 percent of 16-year-olds indicate they have used cannabis on at least one occasion, and 12 percent that they have used it during the past month.
But besides hindering academic performance, recent studies have also found the use of cannabis increases the risk of developing schizophrenia and psychosis, particularly for those with a genetic predisposition to the disorders.
Smoking hashish and marijuana have been suspected to increase the risk of depression, but no conclusive evidence has been found. Otten said this is partly because earlier studies failed to consider individual genetic vulnerability to depression.
Over a five-year period, data were collected from 428 families and their two adolescent children. Each year the children answered questions on topics such as their behavior and depressive symptoms. The variant of the serotonin gene (5-HTT) responsible for increased vulnerability to developing depression was also determined. In young people with a special variant of the gene, cannabis use led to an increase of depressive symptoms.
“The effect is robust,” Otten said. “It still remains, even if you take into account a series of other variables that could cause the effect, such as smoking behavior, alcohol use, upbringing, personality and socioeconomic status.
“Some people might think that young people with a disposition for depression would start smoking cannabis as a form of self-medication, and that the presence of depressive symptoms is therefore the cause of cannabis use. However, in the longer term that is definitely not the case. Although the immediate effect of cannabis may be pleasant and cause a feeling of euphoria, in the longer term we observe that cannabis use leads to an increase in depressive symptoms in young people with this specific genotype.”
The study was published in the online version of the journal Addiction Biology.
Source: Radboud University Nijmegen