Cannabis and mental health: for young people

This webpage gives you some basic facts about cannabis and also how it might affect your mental health.


This is information, not advice. Please read our disclaimer.

Lots of young people want to know about drugs.

Often, people around you are taking them, and you may wonder how it will make you feel. You may even feel under pressure to use drugs in order to fit in, or be ‘cool’.

You may have heard that cannabis is no worse than cigarettes, or that it is harmless. 

The cannabis plant is a member of the nettle family that has grown wild throughout the world for centuries. People have used it for lots of reasons, other than the popular relaxing effect.

It comes in two main forms:

  • resin, which is a brown black lump also known as bhang, ganja or hashish

  • herbal cannabis, which is made up of the dried leaves and flowering tops, and is known as grass, marijuana, spliff, weed, etc.

Skunk cannabis is made from a cannabis plant that has more active chemicals in it (THC), and the effect on your brain is stronger. Because ‘street’ cannabis varies so much in strength, you will not be able to tell exactly how it will make you feel at any particular time.

At present, cannabis is classified under the Misuse of Drugs Act 1971 as a Class B drug. The Advisory Council on the Misuse of Drugs has recommended it be reclassified as Class C, meaning that possession of cannabis would no longer be treated as an offence. However, at present, it is still illegal to possess cannabis.

There are moves afoot to legalise use of cannabis for medicinal purposes and the first emergency licence for cannabis oil was granted on 18 June 2018 for a child with very severe epilepsy.

When you smoke cannabis, the active compounds reach your brain quickly through your bloodstream. It then binds/sticks to a special receptor in your brain. This causes your nerve cells to release different chemicals, and causes the effects that you feel. These effects can be enjoyable or unpleasant.

Often the bad effects take longer to appear than the pleasant ones.

  • Good/pleasant effects: You may feel relaxed and talkative, and colours or music may seem more intense.
  • Unpleasant effects: Feeling sick/panicky, feeling paranoid or hearing voices, feeling depressed and unmotivated.

Unfortunately, some people can find cannabis addictive and so have trouble stopping use even when they are not enjoying it.

Using cannabis triggers mental health problems in people who seemed to be well before, or it can worsen any mental health problems you already have.

Research has shown that people who are already at risk of developing mental health problems are more likely to start showing symptoms of mental illness if they use cannabis regularly. For example if someone in your family has depression or schizophrenia, you are at higher risk of getting these illness when you use cannabis.

The younger you are when you start using it, the more you may be at risk. This is because your brain is still developing and can be more easily damaged by the active chemicals in cannabis.

If you stop using cannabis once you have started to show symptoms of mental illness, such as depression, paranoia or hearing voices, these symptoms may go away. However, not everyone will get better just by stopping smoking.

If you go on using cannabis, the symptoms can get worse. It can also make any treatment that your doctor might prescribe for you, work less well. Your illness may come back more quickly, and more often if you continue to use cannabis once you get well again.

Some people with mental health problems find that using cannabis makes them feel a bit better for a while. Unfortunately this does not last, and it does nothing to treat the illness. In fact, it may delay you from getting help you need and the illness may get worse in the longer term.

If you are at all worried about the effect that cannabis might be having on your mental health, talk to somebody about it. This could be friends, family, or any professional such as:

  • doctor or nurse
  • teacher or school/college counsellor
  • youth counsellor
  • social worker.

There are lots of people who can help you decide whether you do have a problem, and what you can do about it. However, if you don’t talk about it, you are unlikely to get help.

Mental health problems generally do get better if you treat them quickly.

Things that you can do in the meantime to help yourself include:

  • having a day without cannabis
  • avoiding bulk buying
  • avoiding people, places and activities that you associate with cannabis use
  • not using it if you are feeling sad or depressed
  • STOPPING if you get hallucinations
  • seeking help.

"When I was 16, I had my first joint. It was to help me revising for my exams. My friend told me that it would help me relax, and I could revise better.

At first it worked, I felt calmer and more relaxed. But then I started forgetting things I'd revised and stressing myself out more.

I started smoking more and more, and eventually I was relying on weed to cope.

I started smoking more and more every day, and it ended up being the only way that I could enjoy myself and have fun.

My mum noticed that my eyes were always red, but just thought that I was ill. She took me to the doctors who tested my blood, and found out about my drug use. They got me help, and showed me other ways of getting rid of my stress.

I ended up slowly cutting down on my cannabis use, and I have now stopped smoking completely.

When I look back, I realise how silly I was to start smoking so close to my exams. I had to retake a year of sixth form, and really regret developing such a strong addiction to cannabis.

Although it seemed to help at the beginning, it did not help me in the long run. I now know that in order to do well in life, drugs are not the answer."

Below are some websites if you want to know more about the effects of cannabis and other drugs on your mental health and what you can do.

City of London Substance Misuse Partnership - Has produced some useful leaflets to provide information and harm minimisation advice regarding drugs and drug use.

Know cannabis - A website that can help you assess your cannabis use, its impact on your life and how to make changes if you want to.

Talk to Frank - Free confidential drugs information and advice line. Tel. 0800 77 66 00.

YoungMinds - Charity committed to improving the mental health of all children and young people.

Further reading

Rutter’s Child and Adolescent Psychiatry, Fifth Edition (2008). Publisher: Wiley-Blackwell.


  • Fergusson, D. M., Poulton, R., Smith, P. F. et al (2006): Cannabis and psychosis, British medical Journal332:172-175.
  • Patton, G.C., Coffey, C., Carlin, J.B., et al. (2002). Cannabis use and mental health in young people: cohort study, British Medical Journal325, 1195-1198.
  • Maddock, C and Babbs,M (2006). Interventions for cannabis misuse. Advances in Psychiatric Treatment,12:432-439.
  • Di Forti, M. et al (2009): High-potency cannabis and the risk of psychosis. British Journal of Psychiatry,195:488-49.


Revised by the Royal College of Psychiatrists’ Child and Family Public Engagement Editorial Board (CAFPEB).

With grateful thanks to Dr Adam Winstock, Dr Virginia Davies, Dr Vasu Balaguru, and Thomas Kennedy.

This resource reflects the best possible evidence at the time of writing.

About this information

This information reflects the best available evidence at the time of writing. This mental health information for young people was written in 2015.


© 2015 Royal College of Psychiatrists