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Should you act over teenager's cannabis use?

Mrs Cartwright is worried about her 17-year-old daughter Joanna who has become secretive and suspicious. She has found some cannabis hidden in her daughter’s room. Dr Melanie Wynne-Jones considers a tricky presentation

Mrs Cartwright is worried about her 17-year-old daughter Joanna who has become secretive and suspicious. She has found some cannabis hidden in her daughter's room. Dr Melanie Wynne-Jones considers a tricky presentation

Can you discuss Joanna with Mrs Cartwright?

Joanna is over 16 years old and has not consented for you to divulge any of her medical information (assuming she is registered with the practice).

You can tell Mrs Cartwright you are willing to hear her concerns. She may just need to offload and you can assess whether the situation is affecting her own mental health. You can also provide general factual information about the health risks of cannabis, and where Mrs Cartwright could obtain further support and advice.


Must you do anything about Joanna?

If Joanna is registered with the practice, you could have a duty of care if her mental capacity is diminished, so you'll need to make an indirect risk assessment based on what her mother tells you.

What exactly is Joanna doing, and what effect is this having at home, with her friends, or at college? Could this be a family/ interpersonal problem? Joanna's behaviour may be a response to perceived parental interference, or an exaggerated teenage desire for privacy. Does she spend long periods on her mobile or the internet? Who are her friends and what do they do together?

You may need to suggest seeing Joanna – which will be difficult to arrange if she is truly paranoid or simply refuses. If she won't attend, and you think she may be suffering from a severe mental illness, you should discuss the case with your trainer, the local mental health team and/or your medical defence body to see whether you should take action under the Mental Health Act.

How common is cannabis use?

Around two million people in the UK use cannabis: almost 9% of adults aged 16-59 and 10% of under-16s report using it in the past year. It was downgraded to a class C drug in 2004 and in practice the law tends to turn a blind eye to people who possess small amounts for personal use – this is currently under review.

Many people believe cannabis is an ‘entry level' drug that can lead users on to other substances.

Drugs use is more common in 11- to 16-year-olds who have emotional, conduct and hyperkinetic disorders: 20% of young people with emotional disorders reported taking drugs – not just cannabis – compared with 8% of those without. Many people of all ages use cannabis to ‘self-medicate' depression.

What are the adverse effects of cannabis?

Adverse effects are physical, psychosocial and psychiatric. Cannabis is usually smoked, so users are exposed to the hazards of smoking as well as the 400-plus chemicals found in cannabis. Three of the 60 or so compounds it contains bind to cannabinoid receptors in brain areas linked to pleasure, memory, thought and concentration.

This can affect users' work, education and driving skills, and may particularly harm the developing brain. THC (delta-9-tetrahydrocannibol) can depress frontal lobe inhibition of inappropriate thoughts and behaviour and is responsible for the ‘high'. Users may be less vigilant about avoiding hazards such as unprotected sex and risks to personal safety.

Cannabis today is much stronger than in the 1960s and can trigger depression, anxiety or psychotic disorders such as schizophrenia, especially where there is a family background of mental illness. Around one in 10 users may have unpleasant experiences including confusion, anxiety, hallucinations and paranoia.

A recent systematic review suggested users could have a 40% higher risk of developing a psychotic illness, and up to 800 schizophrenia cases a year in the UK could be linked to cannabis use.

What should you do if Joanna presents?

Find out why she came, as this will indicate what you can hope to achieve. Does she acknowledge using cannabis? Has she come because she is worried about her health, or wants help with her drug misuse, or is she here under duress?

Ask about her physical and mental health, and in particular whether she has any depressive or psychotic symptoms. Ask about use of other substances, including alcohol misuse, and discuss the associated health risks, including contraception. How does she perceive her home and family situation? Has she been in trouble with the police or at college?

Does she describe tolerance, cravings or withdrawal symptoms such as irritability and sleep disturbance that suggest dependence? Has she tried stopping it – does she want to, and what is her motivation?

Cannabis can be detected in the urine for up to 56 days after it has last been used, but urine testing is unlikely to be helpful here.

What other help is available?

Many PCTs provide special services for young people with drug and other problems – find out what is available locally. If Joanna is mentally ill you may need to refer her to the mental health services: otherwise the decision is hers, although you can offer support.

Dr Melanie Wynne-Jones is a GP trainer in Marple, Cheshire

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