A definitive review of the addictive propensity of marijuana was undertaken by Eliot L. Gardner under the auspices of the US National Institute on Drug Abuse, National Institutes of Health, and the Department of Health and Human Services.The author stated that “Cannabinoids are euphorigenic (psychoactive) in humans and have addictive liability, but were long considered to be devoid of pharmacological action on these brain reward processes or on drug-seeking and drug-taking behaviours. Work with cannabinoids over the last 15 years, however, makes it clear that they interact with these brain processes and influence drug-seeking and drug-taking behaviours in a manner strikingly similar to that of other addictive drugs.” Further, the author states that “cannabinoid withdrawal appears to activate the same brain withdrawal processes as activated by withdrawal from other addictive drugs.”

Gardner reviewed 224 scientific papers addressing various aspects of addiction, withdrawal, and cannabis use and withdrawal. Of these studies 75 were published in the 1970’s and 80’s and the remaining 149 were published after 1989. The conclusion after examining this plethora of data was that “cannabinoids act on the brain reward processes and reward-related behaviours in strikingly similar fashion to other addictive drugs.