The health effects of marijuana

With the recent election of a new Liberal government, Canadians are becoming more exercised about the possibility of the legalization of recreational marijuana (cannabis) in Canada. In fact, it was one of the few campaign issues that clearly separated the three main parties, with the Liberals advocating full legalization, the NDP decriminalization, and the Conservatives the death penalty (sorry, the status quo). It is an issue with sharp dividing lines and strong opinions, from vehement opposition to unthinking acquiescence to an attitude of almost complete indifference (as in my case).
With that in mind a timely report has come out of the University of Queensland in Australia on the health effects of marijuana. The report, published this week in the respected journal Addiction, examines and summarizes the scientific evidence from 1993 to 2013, a twenty year period during which cannabis use burgeoned throughout the world, and in which the drug itself, and the industry in which it operates, underwent some substantial changes.
Among the findings are:

• People who drive under the influence of marijuana double their risk of being in a car crash.
• About one in 10 daily marijuana users becomes dependent on the drug.
• Adolescents who use cannabis regularly are about twice as likely as non-users to drop out of school.
• Adolescents who use cannabis regularly are also about twice as likely to experience cognitive impairment and psychotic disorders as adults, including disordered thinking, hallucinations, delusions, even full-blown schizophrenia (although some critics argue that it is possible that people with mental health problems may be more likely to use marijuana to begin with, so the link may not necessarily be causal).
• Regular cannabis use in adolescence is linked to some extent to the use of other illicit drugs (the "gateway" effect), although there is still some debate over this.
• Cannabis use in pregnant women may slightly reduce the birth weight of the baby, with all the various health implications that may have for the child.
• While the chances of dying from an overdose of marijuana are almost vanishingly small, there have been several case reports of deaths from heart problems in otherwise healthy marijuana smokers. Middle-aged people who smoke marijuana regularly appear to be at an increased risk of heart attacks.
• The effects of cannabis on respiratory function and respiratory cancer remain unclear, mainly because most cannabis smokers also tend to smoke tobacco (or at least used to).

The report also notes that the content of the main psychoactive ingredient in marijuana (delta-9-tetrahydrocannabinol, or THC) has increased dramatically from about 2% in 1980 to 8.5% or more today. So this is not the relatively innocent Mary Jane of the 1960s. There is also evidence that users generally have not adjusted their doses to account for the increased potency of the drug, thus increasing the risk of accidents and of developing dependency.
All in all, although marijuana is clearly not as dangerous a drug as cocaine, heroin or amphetamines (with which it is often classified in many countries), it does carry many of the same risks as alcohol use, including an increased risk of accidents, dependence and psychosis. It is not a pretty thing, but then neither are alcohol and tobacco, and these are still condoned, albeit less so than heretofore. It seems to me that marijuana belongs in the same category as these legal drugs, and not with cocaine and heroin. Legalize it, regulate it, tax it heavily, discourage it, and get over it.