Cannabis increases the risk of depression in genetically vulnerable

Smoking cannabis increases the risk of developing depressive symptoms, according to research conducted by the Behavioural Science Institute, Radboud University Nijmegen in the Netherlands, and published 'on line' in 'Addiction Biology. Two-thirds of the population have genetic variants associated with depression.

Cannabis increases the risk of developing schizophrenia and psychosis. Furthermore, it believed it could increase the risk of developing depression, but there was no clear evidence on this relationship to date.

The researcher Roy Otten, the Behavioural Science Institute, Radboud University Nijmegen, suspected that this lack of evidence on cannabis use and depression was due in part to earlier research neglected to consider individual genetic vulnerability against depression.

To conduct their research, Otten collected over a period of five years, data from a total of 428 families and their teenage children. Each year, children answered a questionnaire on topics such as their behavior and depressive symptoms.

It was also found in this sample variant of the serotonin gene

(5-HTT) responsible for increased vulnerability to developing depression. In young people with a special variant of the gene, cannabis use led to an increase in depressive symptoms.

"The effect is strong. Remains, even taking into account other variables that could cause this effect, such as smoking, alcohol, education, personality or socioeconomic status," he says.

"Some people may think that young people with a predisposition to depression may start smoking cannabis as a form of self-medication and the presence of depressive symptoms is therefore the cause of cannabis use," he says.

However, according to the researcher, "the long term, definitely, this is not the case." "Although the immediate effect of cannabis can be enjoyable and cause a feeling of euphoria in the long run we have found that cannabis use leads to an increase in depressive symptoms in young people with a specific genotype," he concludes.