Smoking cannabis increases the risk of developing depressive symptoms in young people who are genetically vulnerable to depression, according to scientists at the Behavioural Science Institute of Radboud University Nijmegen.

The results of the study, which involved the collection of data from 428 families, each with two adolescent children, over a five year period, show that apart from an immediate euphoric feeling, the use of cannabis can lead to an "increase of depressive symptoms in the longer term."

Note that two-thirds of the population have the gene variant (5-HTT) that makes one sensitive to depression.

"The effect is robust. It still remains, even if you take into account a series of other variables that could cause the effect, such as smoking behaviour, alcohol use, upbringing, personality and socio-economic 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," says main researcher Roy Otten.

Source: Radboud University Nijmegen