What are drugs and what effects can they have?

Psychoactive substances under international control due to the risk that their use can pose to health, are being referred to as drugs here (1,2). Some of these drugs have a valid medical purpose when used under medical supervision and with a medical indication, for example, morphine for the treatment of severe pain. The non-medical use of drugs can pose a severe risk to health and in some cases can be life-threatening. Drugs affect the brain, especially certain neurotransmitter balances and as such can affect the way the brain works, for example, decision making or motivation.


Drugs under international control include substances such as cannabis, stimulants (e.g. cocaine, amphetamines) or opioids (e.g. heroin) however, cannabis remains the worldwide most used drug. (3).


Substances such as alcohol or tobacco are not under international control and they are legally available in many countries, however rules and regulations differ. These substances also pose a severe risk to public health and therefore countries have agreed on frameworks to prevent and reduce death and disability associated with their use (4,5)


Different drugs have different short-term and long-term effects on the person using them. For a more detailed overview, you can have a look at the UNODC brochure “Get the facts about drugs” that is available here https://www.unodc.org/documents/drugs/printmaterials2014/WDC14_Getthefacts_EN_LORES.pdf (6).


Through the continued exposure to drugs, people can develop drug use disorders and subsequently addiction (7). The onset of drug use and the development of drug use disorders is associated with a complex pattern of vulnerabilities and risk factors. For example, there is a genetic risk to develop a drug use disorder, if many other people in the family have suffered from drug use disorders. Negative experiences in childhood can increase the risk for the development of drug use disorders in later life moreover, the availability of drugs in the neighbourhood might be a risk factor. For a more detailed overview of risk and also protective factors, see the table below:

Adapted from Word Drug Report 2020 (8).


Drug use may cloud the judgement of users. This means that people who use drugs often take more risks, such for example having unsafe sex or driving a car while under the influence of drugs. All these are in turn associated with the risk of sexually transmitted diseases or accidents.


Drug use disorders are associated with several additional negative health and social consequences, depending on the drug used and the mode of using drugs.  Injecting drug use, for example, increases the risk of acquiring infectious diseases such as HIV or Hepatitis and an opioid overdose can lead to death. People with drug use disorders, due to the changes in the brain described above and the compulsory nature of drug use disorders, tend to also have additional social problems, they might lose their jobs or their houses and require support.


People who use drugs and people who develop drug use disorders come from all kinds of backgrounds. They are male and female, young and old, rich and poor, working and unemployed, from the city and the countryside. Drug use and drug use disorders can affect anyone, they are health disorders like others and people with drug use disorders need our help and support.


If you are concerned about your own substance use or that of a family member or a friend, you can visit https://www.huruapp.org/services/ to see treatment centres and contacts that you can reach for additional help, guidance as well as medical and social support.



1.     Centre VI. List of Narcotic Drugs. Drugs. 2004;08469(March 1968):1–23.

2.     Drugs N. The International Drug Control Conventions. Int Drug Control Conv. 2013;

3.  Naciones Unidas. Global Overview: Drug Demand Drug Supply [Internet]. World Drug Report 2021. 2021. 1–113 p. Available from: www.unodc.org/unodc/en/data-and-analysis/wdr2021.html

4.     WHO framework convention on tobacco control. Rev Esp Salud Publica. 2003;77(4):475–96.

5.   WHO. WHO launches SAFER alcohol control initiative to prevent and reduce alcohol-related death and disability [Internet]. [cited 2021 Aug 11]. Available from: https://www.who.int/news/item/28-09-2018-who-launches-safer-alcohol-control-initiative-to-prevent-and-reduce-alcohol-related-death-and-disability

6.     Downey L. Get the Facts. In: Mission Control. 2020. p. 33–60.

7.     Torrence A. Module 2: Understanding Substance Use Disorders, Treatment, and Recovery.

8.   United Nations Office on Drugs and Labour. World Drug Report 2020 (United Nations publication, Sales No. E.20.XI.6). [Internet]. 2020. 56 p. Available from: www.unodc.org/wdr2020