A group of researchers from Canada and the United Kingdom report they have found strong evidence to support that consuming cannabis in adolescence will be more likely to develop depression later in life.
The researchers examined 11 studies from the mid-1990s and onward. They looked at people under the age of 18 who used cannabis for non-medical purposes that were then followed into adulthood to see how had developed clinical depression, anxiety or suicidal behavior. None of the studies looked at all three.
Factors including age, previous mental health issues and socioeconomic status were taken into account. The results of the research did find that there was a strong link between cannabis use and developing these mental health issues later in life. Suicide attempts were found to be 3.5 times higher than those who did not use cannabis before they turned 18. The authors did acknowledge however that the number is imprecise.
“The number of people who are exposed to cannabis, especially in this vulnerable age, is very high and I think this should be a priority for public health and the medical sector as well,” said Dr. Andrea Cipriani, co-author of the research from the University of Oxford.
There is a lot of previous research that points to the idea that because brains are still developing in adolescence that marijuana may have a negative impact on development.
“Now we know that, especially for teenagers, there may be an effect which is biological, with some consequences which can be devastating,” said Cipriani.
The researchers acknowledge that the numbers linking cannabis use in adolescence to depression are modest but that they should not be ignored. They say that more research is required along with education for parents and for teen that deters them from using cannabis during their formative years.
“We know that exposure to higher quantities of THC is associated with an increased risk of harmful effects, whereas another cannabis constituent (cannabidiol) may be protective and potentially beneficial for mental health.”
However, this research does not definitively prove that cannabis use under the age of 18 will result in depression later in life. The researchers could only say that there is a strong link between the two.
King’s College psychiatrist Professor Sir Robin Murray told sources that while it’s likely the findings are correct, the research can’t be considered conclusive. He said that the chance of developing depression as a result of using cannabis during adolescence is less than what has been discovered about schizophrenia-like psychosis. He also said that the strength of the cannabis consumed would need to be a factor but the researchers did not have that information.
“We know from studies of psychosis that the risk is much greater with daily use of modern high-potency cannabis than old-fashioned low-THC varieties,” said Murray.