Drugs – street drugs

About street drugs

These pages are for anyone who takes street drugs and for those who are concerned about them. It gives a brief summary of what is known about the mental health effects of taking the most commonly used street drugs.

They also give information about what help you may expect if you use street drugs and also have mental health problems and therefore have ‘dual diagnosis’.

What are street drugs?

Street drugs are substances people take to give themselves a pleasurable experience, to help them feel better if they are having a bad time or simply because their friends are using them. They include heroin, cocaine, cannabis, alcohol and some prescribed medicines.

All street drugs have effects on mental health – that is why people use them. They are all likely to affect the way you see things, your mood and your behaviour. Unfortunately, while they may give a short-lived burst of pleasure or an exciting experience, many of them have longer-lasting harmful effects and, for some people, they may cause long-term mental health problems.

While a few substances discussed in this booklet are legal, the majority are illegal to possess and to supply to other people. Many drugs, which are now illegal, were originally introduced as medicines. Some of the drugs discussed are used in medicine but are ‘controlled drugs’ – this means that it is illegal to possess them without a prescription written for you and to give or sell them to anyone else; for example, this applies to most benzodiazepine tranquillisers (see below).

The legal status of these drugs is more significantly influenced by the media than by scientific research and does not necessarily reflect the degree of risk they pose to your mental health.

Many street drugs may be mixed with other substances, some of which may be poisonous and increase the risk of harmful effects.

What effect can drugs have on mental health?

The effects that drugs may have on you depend on:

  1. the type of drug
  2. the amount you take
  3. how often you take it
  4. your previous experience of it
  5. what you want and expect to happen
  6. the environment or social situation in which you take it
  7. your mental state

You may react differently to the same drug at different times or in different situations. If you are used to taking a drug in the same place and in the same way, a dose which is safe in that situation may become extremely dangerous if you take it somewhere else, unexpectedly, with no preparation.

Drugs may cause symptoms that are similar to those that lead to a psychiatric diagnosis. In the worst cases drug use may trigger serious conditions such as schizophrenia or long-term depression.

Tolerance and withdrawal

You may become tolerant of some drugs, which means your body gets used to having them, so that you need higher doses to get the same effect.

Withdrawal effects are the body’s reaction when it doesn’t get a drug it has adapted to. They can be stopped, either by taking more of the drug, or by stopping using it completely. This may make you very unwell in the short term and it may take a week or so – or sometimes much longer – to recover.

Dual diagnosis

Some people who have a diagnosed mental health problem may take street drugs to help them cope with their symptoms or with the side effects of prescribed medication (although this is likely to make your problems worse).

Others who previously have had no mental health problems may develop symptoms as a direct result of the drugs they have used.

If you have both mental health problems and problems with street drugs or alcohol use, you may be described as having ‘dual diagnosis’.

What are the different types of street drugs?

There are four main groups of street drugs, divided according to their major effects (or the reason people take them), plus a few substances that do not easily fit into any category.

There are four main groups of street drugs, divided according to their major effects (or the reason people take them), plus a few substances that do not easily fit into any category.

Group Drugs Main effects /reasons for taking them How they work
Stimulants Caffeine, tobacco, amphetamines (amfetamines), ecstasy, cocaine, crack, mephedrone To feel alert, less tired; lift mood They increase brain activity by changing levels of various brain chemicals, including dopamine and serotonin.
Khat To relax and feel elated Interact with the brain chemicals serotonin and noradrenaline
Anabolic steroids To increase stamina. But they also produce mood disturbances Mimic the effects of testosterone
Depressants Alcohol, benzodiazepine tranquillisers To relieve tension and anxiety; help relaxation. They also reduce concentration and self control They increase the action of GABA, a brain chemical that dampens down brain activity
Opium-related pain killers (opiates) Heroin, opium, methadone, pethidine, morphine, codeine, buprenorphine To reduce anxiety; produce feelings of warmth and contentment Opiates reduce sensitivity to physical and emotional pain
Hallucinogens LSD, magic mushrooms (psilocybin), ketamine, phencyclidine (PCP) To heighten senses; have hallucinations; gain feelings of insight. They also make you feel disconnected from your surroundings They interact with several major brain chemicals including serotonin and glutamate
Others Cannabis To relax and feel good; feel spaced out; have hallucinations Interacts with several brain chemicals
Solvents and glues To feel excited; have hallucinations Varies, depending on exact substance


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