Exactly How Evil Is That Weed?

It is difficult to have a discussion about marijuana without ideology, politics and rhetoric getting in the way. Marijuana has been a substance largely associated with the counterculture in North America since at least the 1950s. It has been subject to prohibition and criminal sanctions despite numerous commissions in various countries recommending decriminalization or legalization. Recently, even mainstream Canadian political entities such as the Liberal Party of Canada and former BC Attorney-Generals have advocated for the legalization of marijuana. These calls for an end to prohibition have been based on growing evidence that marijuana is less damaging and costly than many other commonly used legal substances such as tobacco and alcohol and further that prohibition has failed to reduce usage rates and has created a criminal subculture that is harmful to the population.

Because of the political nature of marijuana, there is no shortage of misinformation available about its dangers. So, it's always important to trace claims back to their original research. The main focus of concern from a mental health point of view comes from the established relationship between marijuana use in youth and increased incidence of early onset psychosis. Some advocates conclude from this research that marijuana can cause psychosis or schizophrenia. Most scientific reviewers actually conclude that this is a correlational finding and cause and effect cannot be established. Since the incidence of marijuana smoking is very high and the incidence of psychosis very low, it is more likely that either marijuana acts as a potentiator in those who already have a predisposition to psychosis or that those who are suffering from a pre-existing mental illness are more likely to try to medicate themselves with a substance. It is even more difficult to sort out the effects of chronic marijuana use and early psychosis as some of the early ("prodromal") symptoms of psychosis are common in chronic marijuana users who are not developing psychosis (e.g. withdrawal, lowered concentration, poor sleep, changes in mood, skipping school).

The age of smoking onset and the frequency of use play an important role in assessing the level of concern. Research suggests that chronic smoking before the age of 16 may be associated with more long lasting negative effects such as reduced educational attainment and reduced "grey substance" volume in the brain. The endocannabiniod system on which marijuana acts is most active around the age of 16-17 and is crucial in mediating neural development. The research suggests that there could be a risk for that process to be adversely affected by chronic ingestion of external cannabinoids (marijuana). Most research in this area is of course correlational, and is therefore subject to confounds such as third variables which may cause both marijuana use and long term symptoms (e.g. mental illness, deprivation, family conflict and so on).

A grave concern to parents promoted by anti-drug advocates and denied by cannabis advocates is that marijuana acts as a "gateway" drug making addiction to other drugs more likely. Again, the research is mixed on this subject. While marijuana users are more likely to try other recreational drugs, the vast majority of those who use marijuana, don't go on to use other drugs. It may be that third variables such as pre-existing mental health issues, family problems, peer relationships, or identification with a subculture may determine both marijuana use and other drug experimentation. Early use of alcohol and tobacco may be more potent predictors of later drug use.

What do we do with all this information out there as parents, responsible adults and therapists? First, a little common sense is a good idea. If your teen has occasionally used marijuana in a social situation, that is not in itself a reason to be alarmed (at least 25% of Canadians aged 15-24 have used marijuana in the past year), particularly if all else is going well. However, if you notice changes in behaviour such as withdrawal from normal activities, drop in school performance, mood changes or lethargy it may be good to start a discussion with your teen about these changes. It may be that they are trying to cope with depression, anxiety, sleep problems, peer or family problems by getting high. They may have gotten into a rut where daily use has become a habit which then contributes to making these problems worse. Treatment approaches that target not only the drug use, but also co-occurring problems are the most effective.

Whether you are an adult or a teen, chronic use of a substance such as marijuana or alcohol is best viewed as an indication that there is a problem to be solved. Chronic use may be a way of coping with the normal challenges of life. If you canít get through the day without getting high, or spend all your spare time getting wasted and watching reruns of Family Guy, you likely have some sort of problem coping with life and may possibly have a mental health problem.

There is lots of help out there for substance use and mental health issues. For more information see the links below.

Dr. Jim Browning