Understanding Drugs

What is a drug?

A drug is substance that when taken into the body modify a person’s mental or physical state. ‘Psychoactive drugs’ are substances that affect how the brain works, causing changes in mood, awareness, thoughts, feelings, or behavior. Drugs can make us feel many different things:

  • We can feel good when our life is bad or not feel pain when we are severely hurt, they can produce feelings of increased energy and confidence, or make us feel relaxed and sleepy. Drugs can take us into another reality and cause delusions and hallucinations. Drugs can make us feel happy, more sociably and increases loving and friendly feelings.
  • Drugs can also make us feel nauseous, paranoid and have a serious negative effect on our health, mental health. They can affect our relationships with family and friends. They can take over our lives and make them much worse. In some instances, they can cause us serious harm or may even kill us.

You may have taken drugs or may take them in the future. Even if you never take drugs, you will certainly come across people who have. It is therefore important to have some understanding of drugs.


How drugs work

Effects of psychoactive drugs on the brain

  • A drug gets into your body by swallowing or drinking it, inhaling it as smoke or vapours, by snorting it up your nose, absorbing it through your skin or injecting it into a muscle or vein.
  • Regardless of how a drug gets into your body it travels in the bloodstream to the heart, then passes through a barrier (called the blood brain barrier) into the brain.
  • Once inside the brain a drug temporarily attaches itself to specific areas, called receptor sites. Different drugs attach themselves to different receptor sites – for instance cannabis attaches itself to cannabinoid receptors, while opioid drugs like heroin attach to opioid receptors.
  • The temporary attachment of a drug to its receptor sites influences the brain’s messaging system. This is made up of billions of brain cells called neurons which release chemicals called neurotransmitters. There are over 100 different types of neurotransmitters. Each type (in combination with each other) has a different effect on your mood, feelings, thought process etc.
  • In normal life, the brain constantly adjusts this mix of neurotransmitters in response to events we experience and its own in built desire for survival – for instance flooding the brain with chemicals that make us fall in love to encourage us to reproduce.
  • The affects you feel from a drug occur because the drug has artificially altered this mix of neurotransmitters in your brain. Most drugs affect a neurotransmitter called dopamine, but different drugs affect a different combination of neurotransmitters. For instance, a stimulant drug like cocaine has a major effect on the neurotransmitter ‘noradrenaline’, while an opioid like heroin has a major effect on the neurotransmitter ‘endorphins’.


Effects of drugs on the body

Although psychoactive drugs are mainly taken for their effects on the mind, physical effects make up a large part of the experience. For instance:

  • Heroin can make the pupils of your eyes shrink while cocaine can make them bigger.
  • (MDMA) Ecstasy can cause the muscles of the face and body to tense up, while diazepam can cause them to be more relaxed.
  • An opioid like heroin can cause breathing and heart rate to slow down while a stimulant like cocaine can increase breathing and heart rate.
  • Amphetamine can cause your reflexes to become faster, while alcohol can slow them down.
  • Drugs can also have an effect on digestion include vomiting with a drug like alcohol and constipation with an opioid like heroin.


Types of drugs

There are a number of ways of categorising drugs. Below are six broad categories for the different types of psychoactive drugs:

  • Stimulants
  • Empathogens
  • Psychedelics
  • Dissociatives
  • Depressants
  • Opioids
  • Cannabinoids

(*Categories based on the Drugswheel)


Stimulants drugs speed up both physical functions, such as heart rate and breathing, and mental activity. This may lead to euphoria, increased confidence, energy, and sexual desire and a reduction in appetite. Risks from using stimulants include mood disorders, sudden cardiac arrest, compulsive use and psychosis. Examples of stimulant drugs are nicotine, caffeine, cocaine and amphetamines.


Empathogens (also known as entactogens) are drugs that often have stimulant effects but also produce distinctive emotional and social effects, connection and mutual understanding. The term empathogen, means “generating a state of empathy”. Risks from using empathogens include heat stroke, serotonin syndrome and depression. Examples of empathogenic drugs include MDMA (ecstasy) MDA, MDE, and a number of the synthetic cathinones such as 4-CMC.


Psychedelic drugs, usually have little effect on physical functions, as they work on those parts of the brain which control how the senses operate. They can alter the way in which the individual drug user perceives both their inner and outer worlds and may produce spiritual experiences, perceptual enhancement, euphoria, visual and/or auditory hallucinations. Risks from using psychedelics include, adverse psychological effects, delirium, accidental injury, serotonin syndrome, acute toxicity (poisoning). Examples of psychedelic drugs include LSD, psilocybin mushrooms and 2-CB.


The dissociative are a class of drug that mainly acts on NMDA activity in the brain. This causes people to feel separated or detached from their body or physical environment and can result in euphoria, relaxation, analgesia, visual and/or auditory hallucinations. Risks from using dissociative drugs include, unconsciousness, feelings of intense detachment, temporary paralysis. Examples of dissociative drugs include ketamine and nitrous oxide.


Depressant drugs slow down mental activity and physical functions, such as heart rate and breathing. They produce feelings of euphoria, increased confidence and sociability, disinhibited behaviour. Risks from using depressants include dependence, respiratory depression, reduced blood pressure and heart rate. Examples of depressant drugs include alcohol, GHB, pregabalin and benzodiazepines.


Opioids are drugs that act on opioid receptors in the brain. They relieve pain (analgesia) and cause sedation and produce feelings of invincibility and euphoria. Risks from using opioids include dependence, respiratory depression, reduced blood pressure and heart rate. Examples of opioid drugs include heroin, fentanyl, methadone and codeine.


Cannabinoids are drugs that act on cannabinoid receptors in the brain. They produce feelings of relaxation, euphoria, altered consciousness and sensual arousal. Risks from using cannabinoids may include agitation, seizures, increased heart rate and blood pressure, coma. Examples of cannabinoid drugs include cannabis (THC, CBD) and (‘Spice’) synthetic cannabinoids such as MDMB-4EN-PINACA.


Drug, Set and Setting

Both the effects and the risks involved in using drugs depend on what is known as ‘Drug, Set and Setting’.

Drug – which drug; its strength (purity); how much you take (the dose) and the method of use (smoking, injecting etc).

Set – you: your weight and sex (drugs have a more powerful effect on smaller people); your personality, your genes; your previous drug experience (what you expect to happen) and the mood you’re in.

Setting – where you are and who you are with when you take a drug. For instance using with friends in a safe private place, is less likely to lead to paranoia than taking it in a public place with strangers. Equally, taking drugs and then sitting in an armchair is safer (for everybody) than taking drugs then driving a car.


Dependence and addiction


When you do something you find pleasurable (take a drug, bet on the horses etc), the feeling comes from a boost of dopamine and other neurotransmitters in your brain. The intense desire to repeat this experience is known as ‘craving’.


The pleasurable effect you get when first using a drug, decreases the more of that drug you use. If you use a drug regularly you build up what is known as a tolerance. This means that you need an increasing higher dose to get the desired effect. Tolerance is a warning sign that you may be becoming dependent. With a drug like heroin, an increased tolerance can mean you are using a dose that would have killed you when you first started. If you stop using heroin (e.g. when in treatment or prison) your tolerance drops back down again. If you then go back to using at the same dose, you may overdose and die.

Psychological Dependence

Regular use can mean you start to rely on a drug in social or other situations – your drug use becomes a ‘habit’, which is known as psychological dependence. Any drug can cause psychological dependency.

Physical Dependence

Regular use of some drugs can cause ‘physically dependence’. This means that your brain has effectively ‘re-wired’ itself to expect a dose of a drug. If you stop using, you become physically ill (called a withdrawal). Not all drugs cause physical dependence. Most cigarette smokers and heroin users get unpleasant symptoms when they stop, while with GHB and some heavy alcohol use, sudden withdrawal can be life threatening.


Not everyone who uses drugs becomes addicted to them, in fact most people who use drugs wouldn’t describe themselves that way. Nearly every cigarette smoker becomes addicted, but it is fairly easy to live a ‘normal’ life as a cigarette ‘addict’. Most alcohol users don’t become addicted. Of those that do, some manage to live ‘normal’ lives, whereas for others alcohol takes over there whole life, becoming more important than health, friends, family, self-respect etc. This is what we generally mean when we use the word ‘addiction’.

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