Health risks vary depending on the duration of use, age at the time of use, the nature of the substances, their composition, the method of use, the amount consumed, and the context in which they are used.

In the short term, the risks mainly include acute intoxication, accidents, violence, and unprotected or unwanted sexual intercourse. In the longer term, regular use can lead to the development of dependence. It may be associated with social and economic difficulties and contribute to the development of psychiatric disorders.

Several tools can be used to assess the level of dependence or substance use disorder, such as the CAST questionnaire for cannabis, the 11 criteria of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) created by the American Psychiatric Association, or the 6 criteria of the International Statistical Classification of Diseases and Related Health Problems (ICD-10) created by the World Health Organization.

Drug use: risks related to the nature and composition of products

Each class of substance poses specific risks. Depressants cause respiratory depression, while stimulants present cardiac risks. When multiple substances are used, the risks increase. NPS (new psychoactive substances) lead to overdoses because the dose that produces the desired effect is often close to the dangerous dose. Furthermore, the medium- and long-term risks are often still poorly understood.

In addition to the toxic effects of the substance itself—whose active ingredient content can vary widely—the cutting agents frequently added to these substances can cause unexpected effects and poisoning.

Drug Use: Risks Associated with Methods of Administration

Injecting, smoking, snorting, inhaling, or ingesting are all ways of using drugs. Each of these methods of use presents specific risks: risks of overdose, risks of infection, transmission of viruses (HIV, hepatitis C), injuries or cuts, respiratory diseases…

Drug Use: Risks Related to the Amount Consumed

A potentially fatal overdose occurs when the substance contains a concentration of the active ingredient higher than what the user can tolerate. Deaths from overdose are primarily caused by heroin and other opioid substances.

Drug use: risks related to the context of use

The user’s psychological or physical vulnerability may expose them to risks of discomfort or a bad trip. Certain situations (swimming, driving, etc.) can increase these risks (drowning, accidents, etc.).

Drug use: risks related to poly-substance use

Combined use: A substance user may sometimes consume several legal substances (alcohol, misused medications, nitrous oxide, etc.) or illegal substances simultaneously. When combined, the effects of these substances can be amplified and lead to more serious health risks.

Drug use: risks during adolescence

During adolescence, substance use can impair brain development, potentially leading to mental health disorders. Cannabis can also affect memory, concentration, and motivation.

Drug use: risks during pregnancy

The use of illicit drugs during pregnancy poses specific risks to the baby’s development and health. For some substances, these risks are well identified and documented; but for others, data are lacking. It is difficult to assess the effects because studies often involve small sample sizes, poly-substance use is common, and data are generally self-reported, creating a desirability bias that can be particularly strong on this sensitive topic.

Studies have not identified teratogenic effects—that is, effects likely to cause birth defects—among illicit drugs. The birth defects observed are more likely due to poly-substance use involving alcohol.

Opioid use, through the alternating cycles of use and withdrawal, causes fetal distress that can lead to miscarriage, intrauterine growth restriction, and preterm birth. Close monitoring of the pregnancy and the use of opioid substitution therapy (OST, methadone, or buprenorphine) are recommended for pregnant women who use opioids.

Stimulants used during pregnancy pose the same risks, plus the risk of retroplacental hematoma for cocaine and crack, and preeclampsia for MDMA and amphetamines. At birth, children of women who use drugs may suffer from neonatal abstinence syndrome, which will be properly managed by healthcare teams.

• Learn more: I just found out I’m pregnant

Drug Use and Sexual Activity

“Chemsex” refers to the use of drugs during sexual intercourse. It is distinct from “slam,” which refers to the injection of psychostimulants in a sexual context. It is practiced by men who have sex with men (MSM), but also in heterosexual libertine circles. It most often involves group “hookups,” also known as “chem hookups,” “slam hookups,” “high hookups,” or “slam parties.” "Chemsex users" seek to increase desire, pleasure, and sensations. They hope to feel more sexually capable by taking drugs.
The practice of "chemsex" exposes users to numerous risks to their health and personal well-being: increased risks of addiction and overdose, abscesses, HIV or HCV infection, etc.