So why do drugs affect people differently?

The effects of drugs on young people can be unpredictable and inconsistent. It can vary between people or for the same person on a different occasions. There are three main things that influence the effect of a drug – the environment, the drug and the person.


  • With who and where does the young person use drugs?
  • How safe is it?
  • What is the social setting of their use?

Drug Patterns of their use:

  • How much are they going to use?
  • How often do they use?
  • When do they use – time of day, day of the week?
  • How are they going to use the drug – smoke, eat, inject?
  • Do they use more than one drug at the same time to get a desired effect e.g. using alcohol and cannabis together? (Because alcohol is legal, many people don’t consider it when they then use other drugs and this can be quite dangerous particularly when using other depressants)
  • Do they use other drugs to help manage withdrawal symptoms? e.g. using benzodiazepines to help come down from Ice or to help if they are feeling anxious after using Ice.

Route of Administration:

  • How soon are the drugs felt? (Onset)
  • How strong are the effects? (Intensity)
  • How long do the effects last? (Duration)

Poly Drug Use:

  • Mixing two or more drugs that are capable of interaction is often really unpredictable.


  • The age, gender, weight and general health of the young person and how this might interact with the type of substance being used.
  • The young person’s tolerance and previous experience of the substance including intoxication, after effects and withdrawal.
  • The young person’s past experience with the drug, their expectation and beliefs about it.
  • The young person’s current mood and psychological health and how the substance might impact on this.

Harm Reduction

It is good to consider the above variables before a young person uses a drug and can be a good way to start a conversation about harm reduction with a young person if you know they are going to use something. By asking them these questions you are able to get their own story and position them as the ‘expert of their own use’. Asking a young person some of these questions will help them think a bit more about their use and offer the start to exploring some harm reduction strategies.

Have the conversation:

  • So where are you going to use?
  • Is anyone else going to be with you?
  • Have you used that before?
  • If so, how much did you have?
  • Did you smoke it?
  • How long before the effects wore off?
  • Had you been drinking as well?

Some harm reduction messages from this may be:

  • It is usually a good idea to have someone sober around to keep an eye on things, especially if you’re trying something new or you have a new dealer.
  • Be careful using more than one substance, it can be really unpredictable or increase the risk of overdose.
  • Your mood can really influence the experience you might have on that drug, how has it been for you before when you have been upset?
Further Resources