The health effects of chronic cannabis use

Posted on Mon, 17 Aug 09

During the late 1960s a relatively unheard of drug emerged to become the most popular illicit drug on earth. In contrast to the popular notion that marijuana (Cannabis) is harmless it is problematic for a number of people, especially adolescents, and may have serious health consequences.

A growing concern

Cannabis is the most heavily used illicit drug, approximately 4% of the global population, and the number of people seeking help for addiction is increasing, even in the Netherlands where Cannabis has been decriminalised.  Cannabis dependence is estimated to affect 2% of the general population and is second only to alcohol and tobacco dependence [1].

Health up in smoke

In a recent review on the Chronic Toxicology of Cannabis some 5,000 scientific publications were screened. In this comprehensive review it was found that there is evidence that chronic cannabis use affects mental, cardiovascular, lung, dental and bone health.  Cannabis has been implicated in the development of many major long-term mental health problems including depression, anxiety, psychosis, bipolar disorder, and a low motivational state. Respiratory conditions linked with cannabis include destruction of lung tissue, lung cysts, and chronic bronchitis. Cannabis has been linked to cardiovascular disease and, in a dose-dependent manner, with elevated rates of heart attack. It is also associated with cancer of the lung, head and neck, larynx, prostate, cervix, testes and brain [2].

Cutting back the weed

In frequent users (greater than 3 times a week) cannabis withdrawal commonly results in symptoms such as weakness, increased sleep or insomnia, anxiety, restlessness and depression.  Withdrawal from cannabis results in significant distress and may increase drug use to avoid symptoms. Withdrawal symptoms are typically worse for heavy users [3].

For people seeking treatment for Cannabis dependence structured psychological interventions such as Cognitive Behavioural Therapy have been shown to be effective, and family based interventions may improve treatment in adolescents [4].

Compared to legal recreational drugs such as tobacco and alcohol, high quality evidence clearly defining the health effects of cannabis is lacking. While there may be valid medical applications for Cannabis [5], and while proponents claim it is safer than alcohol [6] the available evidence suggests reason for concern in chronic users.  

References

1. Hall W. The adverse health effects of cannabis use: what are they, and what are their implications for policy? Int J Drug Policy 2009. epub ahead of print April 14, 2009.

2. Reece AS. Chronic toxicology of cannabis. Clin Toxicol (Phila). 2009 Jul;47(6):517-24.

3. Hasin DS, Keyes KM, Alderson D, Wang S, Aharonovich E, Grant BF. Cannabis withdrawal in the United States: results from NESARC. J Clin Psychiatry. 2008 Sep;69(9):1354-6

4. Copeland J, Swift W. Cannabis use disorder: epidemiology and management. Int Rev Psychiatry. 2009 Apr;21(2):96-103.

5. Aggarwal SK, Carter GT, Sullivan MD, ZumBrunnen C, Morrill R, Mayer JD. Medicinal use of cannabis in the United States: historical perspectives, current trends, and future directions. J Opioid Manag. 2009 May-Jun;5(3):153-686.

6. Fox S, et al. Marijuana Is Safer: So Why Are We Driving People to Drink? Chelsea Green Publishing Company, 2009.