Risks & Contraindications

According to the WHO cannabis is a “relatively safe drug“ that has never led to overdose-related deaths. Acute side effects primarily affect the mind and psychomotoric functions as well as the heart and circulatory system. These effects usually vanish after a short period of time. Due to its psychotropic effects cannabis medication is contraindicated for patients suffering from severe personality disorders and who have a higher risk for psychoses. The active substances of cannabis, THC and CBD, are metabolized – like many other pharmaceutical substances – via the hepatic cytochrome P450 system (CYP450), which may result in interferences with other drugs. The abuse risk of cannabis is very low compared to other substances. Nevertheless, the long-term, heavy use of cannabis, especially during adolescence, can lead to psychological and behavioral disorders and should therefore be therapeutically clarified and monitored.

Is cannabis a dangerous drug?

In 2018 the World Health Organization (WHO) re-rated the risk of using cannabis (here: recreational use): According to this, cannabis is a ”relatively safe drug“ which – other than heroin, cocaine or even legal substances like alcohol, nicotine and various pharmaceuticals – has never led to overdose-related deaths. At most, potential side effects such as an impaired short-term memory, motor coordination and potential risks for the cognitive development of adolescents need to be considered.1 In contrast, the use of synthetic cannabinoids, so called ”legal highs“ (Spice, Bath Salts), recently led to the death of several teens.

What side effects does cannabis have?

Each substance that has an effect will also bring unwanted side effects – this is of course also the case with cannabis. Cannabis extracts, flowers or other cannabinoid agonists (i.e. Dronabinol, Nabilon) that are rich in THC show a comparable range of side effects mainly mediated by CB1 receptor activation: acute side effects primarily effect the mind and psychomotoric function, as well as the heart and circulation (tachycardia, drop in blood pressure, dizziness, syncope). These effects usually vanish after a short acclimatization phase. Above an individual dosage threshold, psychotropic effects are common. These are usually perceived as pleasant and relaxing and can therefore be used therapeutically. However, for some, these effects can also turn into dysphoria, anxiety and panic.2,*

Further known side effects are dryness of the mouth, increased appetite, decreased formation of tears and reddening of the eyes, altered perception of time and senses, disruptions in orientation and balance, and muscle relaxation.

Due to its psychotropic effect cannabis medication is contraindicated for specific patient groups (patients suffering from severe personality disorders and who have a higher risk for psychoses).

For further details please ask your physician.

* This may indicate a so-called ”challenging psychedelic experience“ (due to its effect on the serotonergic system cannabis might act as a weak psychedelic), that is characterized by anxiety, feeling of loneliness and captivity, disorientation in terms of time and space, confusion and the fear of losing control. Psychedelic states can potentially bring up trauma and fear from the subconscious to the waking consciousness. It is possible to utilize even challenging experiences therapeutically with support of an appropriately-trained professional.4 Self-governed harm-reduction organizations like the Zendo Project and Eclipse e.V., as well as scientific organizations like MIND European Foundation for Psychedelic Science offer trainings and information material for physicians, therapists and private persons.

Do interactions between cannabis and other pharmaceuticals exist?

Both, THC and CBD are metabolized – like many other pharmaceutical substances – via the hepatic cytochrome P450 system (CYP450). THC primarily via CYP3A4 and CBD via CYP2C19 and CYP2D6. When used simultaneously with other pharmaceuticals that are metabolized by the same enzymes, the concentration levels of the respective drugs may mutually interfere.3

The simultaneous intake of hypnotics, sedatives or other sedating substances (also alcohol) can lead to an additional effect in sedation and muscle relaxation.4

For further details please ask your physician.

Abuse potential

A study published in 2007 by Nutt et al. in Lancet shows that the abuse potential of cannabis is far lower than that of illegal narcotic drugs like heroin or cocaine, but also of many prescription drugs like buprenorphines, benzodiazepines and barbiturates and legally available luxury goods like alcohol or tobacco.5

Figure 1: Mean harm scores for 20 substances
Classification under the Misuse of Drugs Act, where appropriate, is shown by the colour of each bar.

Developing a psychological addiction in a therapeutic context is very unlikely, especially with moderate doses. However, the permanent medication with THC-containing pharmaceuticals usually leads to the development of tolerance (strictly speaking, to a mild physical ”addiction“). Primarily, this adaptation leads to the vanishing of unwanted side effects like fatigue, dizziness, cardiovascular and psychological effects after some time. A sudden termination of the medication can temporarily lead to mild withdrawal symptoms (like insomnia, irritability, increased sweating.2

Despite of the relatively low abuse potential, permanent and heavy use of cannabis (especially during adolescence) can lead to psychological and behavioral disorders (e.g. psychological addiction, psychotic episodes). According to the international statistical classification of diseases and related health problems these disorders are characterized with the code ICD-10 F12. It has not finally been clarified whether cannabis consumption causes these diseases or whether the use of cannabis merely correlates with psychological problems; in the latter case, using cannabis could be seen as attempted self-medication.6,7

Psychological disorders, crises and addiction are usually accompanied by a tendency towards social isolation. Since cannabis consumption is illegal in many countries, affected people often do not seek help out of fear or shame, even if they suspect harmful cannabis use in themselves or relatives, which probably further aggravates the situation. In case you suspect problematic cannabis use for yourself, talk about it with your physician, family or friends. Furthermore, you can find information and consolatory services on the internet that is designed especially for cannabis users looking for professional help.

[1] http://www.who.int/medicines/access/controlled-substances/Section3.CannabitPlant.Toxicology.pdf

[2] Cannabis: Verordnungshilfe für Ärzte von Franjo Grotenhermen; Klaus Häußermann – ISBN 10: 3804737595 – ISBN 13: 9783804737594

[3] Whiting PF et al. (2015): Cannabinoids for Medical Use ‐ A Systematic Review and Meta‐analysis. In: JAMA 2015;313(24):2456‐2473. doi:10.1001/jama.2015.6358

[4] Jungaberle H, Thal S, Zeuch A, et al. Positive psychology in the investigation of psychedelics and entactogens: A critical review. Neuropharmacology. June 2018. doi:10.1016/j.neuropharm.2018.06.034

[5] 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

[6] Bolhuis K, Kushner SA, Yalniz S, et al. Maternal and paternal cannabis use during pregnancy and the risk of psychotic-like experiences in the offspring. Schizophr Res. July 2018. doi:10.1016/j.schres.2018.06.067

[7] Sami MB, Bhattacharyya S. Are cannabis-using and non-using patients different groups? Towards understanding the neurobiology of cannabis use in psychotic disorders. J Psychopharmacol. 2018;32(8):825-849. doi:10.1177/0269881118760662