Depressants – overview of effects
| Substance |
How it works |
Tolerance |
Withdrawal |
Effects of prolonged use |
| Ethanol (alcohol) |
Alters the effects of the neurotransmitters glutamate and GABA.
Probably increases activity in the dopamine system involved in motivation and learning. |
Develops due to increased processing in the liver and changes to receptors in the brain. |
Withdrawal from long-term use can include shaking, sweating, weakness, agitation, headache, nausea, vomiting, seizures, and delirium tremens. |
Changed brain function and structure, reduced mental capacity, decreased brain volume. |
| Hypnotics and sedatives |
Enhances the effects of some neurotransmitters (e.g. GABA). |
Develops quickly due to changes in brain receptors. |
Anxiety, alertness, restlessness, insomnia, excitability, seizures. |
Memory problems. |
| Inhalants (volatile solvents) |
Like other sedatives and hypnotics, probably affect specific transmitters.
Increases activity in the dopamine system involved in motivation and learning. |
Some tolerance develops, but is difficult to estimate. |
Increased susceptibility to seizures during withdrawal |
Changes in how dopamine works in the body, problems in the nervous system, reduced mental capacity; psychiatric problems. |
Stimulants - overview of effects
| Substance |
How it works |
Toleranc |
Withdrawal |
Effects of prolonged use |
| Nicotine |
Activates specific receptors. Increases the production and release of dopamine. |
Develops through metabolic factors, as well as receptor changes. |
Irritability, hostility, anxiety, unease, discomfort, depressed mood, decreased heart rate, increased appetite. |
It is difficult to separate the health effects due to nicotine from the effects due to other components of tobacco. |
| Cocaine |
Prolongs the effects of transmitters such as dopamine. |
Perhaps short-term tolerance. |
There is not much evidence of withdrawal.
Depression is common among dependent people who stop using the drug |
Abnormalities in specific regions of the brain, loss of some mental capacity, problems with movement, decreased reaction times. |
| Amphetamines |
Increase the release and prolong the effects of dopamine and related transmitters. |
Develops quickly |
Fatigue, depression, anxiety and intense craving for the drug. |
Sleep disturbances, anxiety, decreased appetite; changes in dopamine brain receptors, changes in metabolism in some parts of the body, reduction of mental capacity and deterioration of movement. |
| Ecstasy |
Increases the release and prolongs the effects of the neurotransmitter serotonin. |
May develop in some individuals. |
Depression and insomnia |
Damages some brain systems, leads to physical changes and to changes in behaviour.
Long-term psychiatric and physical problems such as loss of memory, problems with decision-making and self-control, paranoia, depression and panic attacks. |
Opioids – overview of effects
| Substance |
How it works |
Tolerance |
Withdrawal |
Effects of prolonged use |
| Opioids |
Activate specific receptors that are abundant in an area of the brain that is involved in motivation and learning. |
Due to short-term and long-term receptor changes, and to changes in the way some cells communicate. |
Can be severe.
Watering eyes, runny nose, yawning, sweating, restlessness, chills, cramps, muscle aches. |
Long-term changes in certain receptors.
Changes in learning and in the response to stress. |
Hallucinogens – overview of effects
| Substance |
How it works |
Tolerance |
Withdrawal |
Effects of prolonged use |
| Cannabis |
Activates specific receptors.
Affects the dopamine system involved in motivation and learning. |
Develops quickly. |
Withdrawal is rare perhaps because cannabis remains in the body for a long time. |
Long-term exposure may produce long-lasting reduction of mental capacity.
May make mental illness worse. |
| Hallucinogens (such as LSD and PCP) |
Different substances in this class act on different brain receptors. |
Develops quickly. |
There is no evidence of withdrawal. |
Short or long term disturbed mental state in which a person experiences hallucinations, delusions, personality changes and loss of contact with reality.
Flashbacks or re-experiencing of drug effects, long after drug use. |
Source: WHO: GreenFacts based on Table 4
 Neuroscience of Psychoactive Substance Use and Dependence, Summary (2004),
Global use of psychoactive substances and burden to health, p 18-19
Related publication: Other Figures & Tables on this publication: Table 1. Prevalence of smoking among adults and youths in selected countries Table 3. Percentage of total global mortality and DALYs attributable to tobacco, alcohol and illicit substances Depressants – overview of effects Table 5. Pharmacological treatments for substance dependence Table 2. Annual prevalence estimates of global illicit substance use, 2000-2001Table 2. Annual prevalence estimates of global illicit substance use, 2000-2001 Figure 3. A terminal button and synapse Figure 4. Two types of chemical synapses Table 4. Summary of psychoactive substance effectsTable 4. Summary of psychoactive substance effects Figure 5. Mesolimbic dopamine pathway Box 3. Risk and protective factors for substance use Figure 1. Adult (15+) Per Capita Alcohol Consumption by Development Status Figure 2. Mechanisms relating psychoactive substance use to health and social problems Box 4: Types of psychotherapies and behavioural interventions Box 1: Injecting substance use and HIV/AIDS Box 2: Criteria for substance use dependence in ICD-10 |
