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Visions Journal

A reminder that this article from our magazine Visions was published more than 1 year ago. It is here for reference only. Some information in it may no longer be current. It also represents the point of the view of the author only. See the author box at the bottom of the article for more about the contributor.

Cannabis: A mental challenge

Mark A. Ware, MBBS, MRCP, MSc

Reprinted from the "Cannabis" issue of Visions Journal, 2009, 5 (4), p. 13

How the effects of cannabis use on mental health has been reported—and the way people look at this information—has a long and colourful history. Cannabis use goes back thousands of years. But the current pattern of use—smoked cannabis and oral preparations like extracts, infusions and edibles, for both recreational and medicinal purposes—is relatively recent. Cannabis use as we know it today can be traced back to India in the 1800s and into Europe and North America in the 1900s.1

Cannabis through the last century

In the 1920s, reports from the United States of cannabis use turning healthy people into raving lunatics were cited by Emily Murphy in her book The Black Candle.2 (Murphy was a police magistrate and judge of the juvenile court in Edmonton.) Her work played a pivotal role in the eventual criminalization of cannabis in Canada in 1923.

In the mid 1950s, the 1930s film Reefer Madness created a new wave of concerns about the effects of cannabis use among young people. The movie, a cautionary tale, claimed that cannabis caused people to behave in morally dreadful ways, with tragic results—insanity, loss of sexual inhibitions and violence. (The film is now a cult classic comedy film because of the comedy of its exaggerated claims and style of presentation.)

In the 1970s, the term ‘cannabis psychosis’ emerged, following case reports where cannabis use was seen to cause psychotic behaviour.3 In the following decade, the concept of a cannabis-induced ‘amotivational syndrome’ was also introduced. This syndrome refers to users allegedly becoming lazy and dropping out from a conventional productive life.4

Within the past 10 years, high-quality studies have concluded that recreational cannabis use in young adults is associated with an increased risk of schizophrenia.5

As with so many controversies in public health, the cannabis story is not a simple one.

Looking for answers

Cannabis is widely used in Western society. It’s so widely used that cannabis experimentation may even be seen as part of normal adolescent behaviour. Over 47% of Canadians ages 18 to 19 used the drug in 2004.6 Cannabis known to be the most widely used recreational drug in the world.7

In contrast to the ‘alarm bells’ mentioned in the previous section, current research belies some of those statements and points to some benefits of cannabis use. It has been reported that cannabis use has no permanent effects on long-term cognitive function.8 Some reports show that cannabis-based medicines may be useful in easing symptoms of attention-deficit hyperactivity disorder (ADHD)9 and post-traumatic stress disorder.10 The synthetic cannabinoid drug nabilone was shown in the 1970s to be an effective treatment for anxiety.11 There has been no epidemic of schizophrenia over the past 40 years, even though cannabis use has increased.12

So, where is the truth to be found?

Opening our minds

It’s likely that the truth is buried somewhere in these pages. This issue of Visions explores the role of cannabis in a wide variety of mental health issues, from many different perspectives. It’s up to you, the reader, to reflect on these issues and decide where the arguments are made most rationally.

Some cautions are probably worth noting as you approach this issue, however. First, the cannabis debate is highly polarized. There are those who feel strongly that cannabis use should be legalized and taxed like alcohol and tobacco. And there are those who feel it should remain a criminal activity. Each side uses evidence to support their claims or either the safety or the dangers of cannabis. It is remarkable that for every study showing cannabis has harmful effects on mental health, there are others that show the opposite. Systematic reviews, which combine and judge all available scientific studies for quality before drawing conclusions, are expensive, time consuming and require specialized expertise. They are, therefore, extremely rare. So it is important to take note of who has written the piece you are reading and what their sources of information are. Don’t be afraid to do your own checks and your own homework.

A second thing to keep in mind is that cannabis is an illegal drug—with the exception, in Canada, of authorized medical users. Therefore, almost all research done on cannabis worldwide has been conducted on an illegal drug. It’s not clear what effect this has on the quality of the data generated. But it’s naïve to think that estimates of cannabis use and its effects are not biased. The social stigma or legal implications of admitting illegal drug use or of admitting the need for ‘treatment’ for cannabis use may influence a person’s response. The question is not whether such bias exists—it surely does—but how much this bias affects the validity of the data.

Third, all of us living in North America have likely had some exposure to cannabis use. This could be via friends or family members, and/or it could be our own experience of use. The media also plays a huge role in our awareness of cannabis issues. Our exposure may be positive, negative or even completely neutral.

The fact remains that we each approach the topic of cannabis use from our personal perspective. It’s worth reflecting on our own feelings about cannabis as we explore the work of others. I encourage you to ask yourself whether, in the face of good-quality evidence, you would actually change the way you currently think. Be open minded and reasonable—and the truth will likely reveal itself.

About the author
Dr. Ware is Assistant Professor in Anesthesia and in Family Medicine at McGill University. He is also Director of Clinical Research at the McGill Health Centre Pain Clinic. His primary research interest is the evaluation of patient-driven pain treatments, including cannabis and complementary therapies such as dietary supplements, meditation and yoga
  1. Russo, E.B. (2007). History of cannabis and its preparations in saga, science, and sobriquet. Chemistry and Biodiversity, 4(8), 1614-1648.

  2. Murphy, E.F. (1922).The Black Candle. Toronto: Thomas Allen.

  3. Milman, D.H. (1969). Marihuana psychosis. Journal of the American Medical Association, 210(13):2397-1298.

  4. Creason, C.R. & Goldman, M. (1981). Varying levels of marijuana use by adolescents and the amotivational syndrome. Psychological Reports, 48(2):447-454.

  5. Moore, T.H., Zammit, S., Lingford-Hughes, A. et al. (2007). Cannabis use and risk of psychotic or affective mental health outcomes: A systematic review. Lancet, 370(9584), 319-328.

  6. Health Canada. (2005). Canadian Addiction Survey: A national survey of Canadians’ use of alcohol and other drugs: Prevalence of use and related harms: Detailed report.

  7. United Nations Office on Drugs and Crime. (2009). Release of World Drug Report 2009 [media release].

  8. Grant, I., Gonzalez, R., Carey, C.L. et al. (2003). Non-acute (residual) neurocognitive effects of cannabis use: A meta-analytic study. Journal of the International Neuropsychological Society, 9(5), 679-689.

  9. Strohbeck-Kuehner, P., Skopp, G. & Mattern, R. (2008). Cannabis improves symptoms of ADHD. Cannabinoids 3(1), 1-3.

  10. Fraser, G.A. (2009). The use of a synthetic cannabinoid in the management of treatment-resistant nightmares in posttraumatic stress disorder (PTSD). CNS Neuroscience & Therapeutics,15(1), 84-88.

  11. Glass, R.M., Uhlenhuth, E.H. & Hartel, F.W. (1979). The effects of nabilone, a synthetic cannabinoid, on anxious human volunteers [proceedings]. Psychopharmacology Bulletin, 15(2), 88-90.

  12. Frisher, M., Crome, I., Martino, O. et al. (in press). Assessing the impact of cannabis use on trends in diagnosed schizophrenia in the United Kingdom from 1996 to 2005. Schizophrenia Research.


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