Largest Epidemiological Study not Mentioned

Risks Associated With the Non-Medicinal Use of Cannabis by Dr. rer. nat. Eva Hoch, Prof. Dr. med. Udo Bonnet, Prof. Dr. med. Rainer Thomasius, Dr. med. Florian Ganzer, Prof. Dr. med. Ursula Havemann-Reinecke and Prof. Dr. med. Ulrich W. Preuss in issue 16/2015

Unfortunately, the authors did not wholly succeed in explaining the risks of cannabis in a differentiated manner (1). With regard to the selection of studies of possible tumor disorders subsequent to cannabis consumption, it is of note that the largest and most elaborate epidemiological study was not mentioned (2). As in other studies that were not included, this study did not find any risk increase owing to cannabis smoking for any of the cancers under investigation—including cancers of the respiratory tract. Tetrahydrocannabinol (THC) itself inhibits cancer.

With regard to the association between early cannabis consumption and premature dropping out of school, studies that investigate the causality are lacking. One study of 3337 adult twins found that the relation between cannabis consumption at a young age and dropping out of school early is based on common environmental risk factors that affect the risk for cannabis consumption at a young age as well as dropping out of school prematurely (3).

The authors concede that studies of suicidality have yielded heterogeneous results, but they documented only studies reporting increased risks for suicidal ideation. Other studies that, for example, investigated the association between legislation concerning the medicinal use of cannabis in the US and suicide rates did not find any significant association with completed suicides (4).

Increasingly, there are indications that some cannabis effects, such as an anti-inflammatory effect and neuroprotection, may have beneficial effects in the long term. A 2015 meta-analysis of eight studies from the US, on the basis of the National Health and Nutrition Examination Surveys and the National Surveys on Drug Use and Health, confirmed that cannabis consumption might have a protective effect against the development of diabetes. Cannabis consumption was associated with a 30% reduction in the risk of diabetes (odds ratio 0.7; 95% confidence interval 0.6 to 0.8).

DOI: 10.3238/arztebl.2016.0009b

Dr. med. Franjo Grotenhermen

Nova-Institut

Hürth

Conflict of interest statement

The author is the chair of the working group Cannabis as Medicine reg. assoc. (Arbeitsgemeinschaft Cannabis als Medizin e V [ACM]), chair of the Medical Cannabis Declaration reg assoc (MCD), and managing director of the International Association for Cannabinoid Medicines reg assoc (IACM).

References

1. Hoch E, Bonnet U, Thomasius R, Ganzer F, Havemann-Reinecke U, Preuss UW: Risks associated with the non-medicinal use of cannabis. Dtsch Arztebl Int 2015; 112: 271–8.

2. Hashibe M, Morgenstern H, Cui Y, et al.: Marijuana use and the risk of lung and upper aerodigestive tract cancers: results of a population-based case-control study. Cancer Epidemiol Biomarkers Prev 2006; 15: 1829–34.

3. Verweij KJ, Huizink AC, Agrawal A, Martin NG, Lynskey MT: Is the relationship between early-onset cannabis use and educational attainment causal or due to common liability? Drug Alcohol Depend 2013; 133: 580–6.

4. Grucza RA, Hur M, Agrawal A, et al.: A reexamination of medical marijuana policies in relation to suicide risk. Drug Alcohol Depend 2015, 152: 68–72.