When comparing the abuse potential of a substance in terms of a) potential health damages, b) addictive potential and c) associated social damages, surprisingly you will not find that high risk substances are illegal and low risk substances are legal. The abuse potential of cannabis is far lower than that of illegal narcotics, such as heroin or cocaine, but also lower than the one of several prescription drugs as well as legally available luxury goods such as alcohol or tobacco.
One of the major concerns with the prescription of medical cannabis is its abuse potential as an addictive drug. After all, the medicinal plant was falsely classified as narcotic drug without any medical benefit for decades. There are three major factors6 that determine the abuse potential of a substance: possible acute health hazards for the consumer; the tendency of the drug to be addictive; and the social effects of drug consumption (on family, community and society).
The health hazard6 for the consumer can further be distinguished into
- a) acute physical damages – meaning direct risks (i.e. respiratory depression with opioids, acute myocardial infarction with cocaine and fatal poisoning),
- b) chronic physical damages – meaning effects on health caused by long-term usage (i.e. psychosis with stimulants/sleep deprivation, lung disease with tobacco) and
- c) specific problems in connection with intravenous application (virus infections etc.).
Cannabis virtually cannot be fatally overdosed in the human body (according to experts an intake of several hundred grams of cannabis flowers would be necessary within a few minutes; even strong consumers do not use more than 5 grams per day)1. Occasional and little cumulative consumption (here: smoking) apparently does not even harm lung function as shown in a long-term study; there are even indications pointing to an anti-cancerogenic effect of cannabis in some tumors of the lung.2,3
The addictive potential6 of a substance is determined by the extent of the pleasant effect the drug has (dopaminergic reward system of the brain) on the one hand, and in what way it leads to addictive behavior on the other hand. The more rapid a psychotropic substance flushes the brain, the more intense the intoxication / the “kick“. Hence, street drugs are preferably applied intravenously or via the nasal mucosa or the lungs in order to reach the blood stream directly. Oral intake of the same substances causes a slower uptake by the body and a decreased intoxication (or less influence on the dopaminergic reward systems, respectively), although the effects usually last longer after oral intake. Physical dependence or addiction is mostly a result of an increased physical tolerance (e.g. by adaptive desensitization or numerical down-regulation of the involved receptors); higher drug doses are required for the same effects. It manifests as an intense desire for the drug (craving) when the consumption is interrupted, as well as physical withdrawal symptoms like pain, tremor, diarrhea, sweating or insomnia. Headache, irritability and nausea e.g. during caffeine “withdrawal” are also signs of physical depencence. Psychological addiction is a result of habitually repeated use of a substance that is rather based on an urge than on the attempt to interrupt physical withdrawal symptoms.
Social damages6 are the result of e.g. different secondary effects of the intoxication (i.e. accidents and violence with alcohol), of harmful impact on family and social life (e.g. neglect, lack of interest) and of arising costs for health care system, social care and police force. Drugs that lead to heavy intoxication are associated with high costs in terms of collateral damages for the consumer, their fellow humans and property (e.g. also drug-related crime).
As it is generally known, drug-related crimes (prostitution, robbery, theft) play a negligible role for cannabis consumers, if you do not count in the mere acquisition of the illegal plant. Furthermore, three years post-legalization of cannabis in several US states there was no proof for a difference in traffic accident fatalities in comparison to states without legalization.5
Based on these factors (individual health hazard, addiction potential and social damages), Nutt et al. calculated and compared the abuse potential of several substances in a study6 published in Lancet in 2007. It was surprising that the rational-objective assessment by no means showed that high-risk substances are illegal and low-risk substances are legal (see Fig. 1).
According to this study the abuse potential of cannabis based on the rational criteria presented here, is far lower than could be assumed by its reputation: It ranks far below other illegal narcotics such as heroin or cocaine, and is also lower than the abuse potential of many prescription drugs such as buprenorphines, benzodiapines and barbiturate, as well as of legally available luxury goods such as alcohol and tobacco.
 Pletcher MJ, Vittinghoff E, Kalhan R, et al. Association Between Marijuana Exposure and Pulmonary Function Over 20 Years. JAMA. 2012;307(2):173. doi:10.1001/jama.2011.1961
 Velasco G, Hernández-Tiedra S, Dávila D, Lorente M. The use of cannabinoids as anticancer agents. Prog Neuro-Psychopharmacology Biol Psychiatry. 2016. doi:10.1016/j.pnpbp.2015.05.010
 In the Realm of Hungry Ghosts: Close Encounters with Addiction; Gabor Mate M.D., Peter A. Levine Ph.D.; ISBN: 8580001069746
 Aydelotte JD, Brown LH, Luftman KM, et al. Crash Fatality Rates After Recreational Marijuana Legalization in Washington and Colorado. Am J Public Health. 2017;107(8):1329-1331. doi:10.2105/AJPH.2017.303848
 Nutt D, King LA, Saulsbury W, Blakemore C. Development of a rational scale to assess the harm of drugs of potential misuse. Lancet (London, England). 2007;369(9566):1047-1053. doi:10.1016/S0140-6736(07)60464-4