Cannabis Facts – For Parents

CANNABIS – THE FACTS (& information for parents) – 2020

Five years ago, 95 per cent of psychiatrists would have said that cannabis doesn’t cause psychosis. Now I would estimate that 95 per cent of them would say it does’. Professor Robin Murray, Institute of Psychiatry, London.

As the Chief Constable of Merseyside said recently:

‘An elephant has walked into the room and nobody’s noticed; that elephant is skunk cannabis.’


  • It is not the same stuff as you may have smoked at college in the 60s, 70s, and 80s and can have devastating effects on the young.
  • THC (the chemical that gives the high) has increased in the new super-strength cousin of cannabis – sinsemilla (called ‘skunk’ because of its pungent smell). Average THC in skunk is 16%, sometimes more. This is much higher than the herb (1-3%) and the resin (4-6%)    Another chemical present in cannabis is cannabidiol (CBD), occurring in negligible amounts in the stronger strains. CBD is thought to contain antipsychotic properties, counteracting the effects of THC. Smaller amounts in skunk may account for the commonly reported psychotic reactions.
  • Interestingly, CBD appears to have been virtually bred out of skunk, which may account for the devastating effects we are seeing, especially among the young.
  • Some statistics: in 2007 ‘The Lancet’ reported that cannabis users are 40 per cent more likely to develop psychotic symptoms than non-users. Within the past 2 years the Royal College of Psychiatrists has reported that more than 80 per cent of those being treated for their first psychotic episode had used skunk.
  • Police findings: about 80% of the cannabis seized in Britain today, and mostly grown here in “factories”, is the stronger skunk type. These factories are often set up in suburban houses, with a ‘gardener’ (often a child, so linking this crime with people-trafficking too), and run by criminal gangs. Hydroponic techniques are highly sophisticated and produce masses of the new skunk varieties.
  • Cannabis is fat-soluble, unlike most other commonly-used drugs (which are water-soluble). As a result brain functioning can be affected for a long time, cannabis is not excreted by the body for 5 – 12 weeks.
  • Impact on mental health: all the neurotransmitters of the brain are affected due to THC sitting in cells. This has serious consequences for developing brains – remember that the brain does not finish its development until the 20’s.
  • Professor Robin Murray and his team at the Institute of Psychiatry have been conducting research whereby healthy volunteers with no history of mental illness are given THC. All have had psychotic symptoms, proving we now know that THC causes psychosis – it is just a matter of the amount given.  ’Findings confirm that THC can induce a transient, acute psychotic reaction in psychiatrically well individuals’, PD Morrison et al, Psychological Medicine, 2009. Dr Marta di Forti from Professor Murray’s team has also recently (December 2009) published new research showing that skunk users are 18 times more likely to suffer psychosis.
  • Immediate effects that have been noted: paranoia is common as are panic attacks, and loss of contact with reality (psychosis).
  • Cannabis affects the body not just the mind:  lungs, cardiac, digestive, immune and reproductive systems are all affected.
  • Driving (and piloting) ability can be severely impaired even 24 hours after a joint, studies have found.
  • Government findings: Latest figures (2009, from ‘Smoking Drinking and Drug Use’, Home Office) show that the age of first use is falling – the average age of beginning is 13. Cannabis is the drug of choice for 14-15 year olds. Only 1 per cent of parents think their child may be using drugs. Youth magistrates report seeing children as young as 9 or 10 becoming involved in crime to support a cannabis habit.
  • Treatment: September 2008, Mike Trace (CEO of RAPT) spoke of the urgent need for residential centres for young addicts (under 18s). Only 20 per cent of residential rehab beds in the UK are for adolescents with little provision for emergency intake.
  • Rehab referrals from GPs rarely occurs.
  • Earlier this year the National Treatment Agency published the figure of 25,000 young people under the age of 18 getting treatment for drug and alcohol problems – up 8,000 on figures produced 18 months before. (NTA, ‘Getting to Grips with substance misuse amongst young people’ 2008).
  • Long-term Effects: cannabis is psychologically and physically addictive.
  • Physical dependence happens when cannabis takes the place of the natural neurotransmitter anadamide in the brain. Because the cannabis is substituting this naturally occurring chemical, production of the natural chemical is greatly reduced. Latest research (Nov 2009, Morgan et al) shows that humans can develop physical dependence on cannabis, especially if they have become tolerant to it.
  • When the drug is stopped receptor sites are left empty. They have to be filled otherwise withdrawal set in, which can produce irritability, tiredness, restlessness, sleeplessness, anxiety, depression and sometimes violence (especially with ‘come down’ or withdrawal).
  • Psychological dependence: ingrained belief that normal life would be impossible without the drug.
  • More youngsters are being treated in the USA for marijuana addiction than for alcohol. Anxiety, depression, apathy, decline in academic performance, negative impact on cognition, and opting out are all common among young cannabis users.
  • A permanent presence of the drug can be detected in cannabis users with just one joint a week, or even a month – the THC does not have chance to leave the body and brain.
  • Chance of developing psychosis: 1 in 4 four of us carries a faulty gene for dopamine transmission (the neurotransmitter in the brain – the amount is increased). Cannabis use in adolescence: if a young person has one copy of this gene the chances of a psychotic illness is raised by 5 to 6 times, if copies have been inherited from both parents, the risk is ten-fold.  (Caspi et al 2005)
  • Schizophrenia is usually a chronic (long-lasting) or often lifetime condition. There is evidence that cannabis users increase their chances of developing this condition by two or three times. In scans of the brain, similar damage has been seen in the brains of daily adolescent cannabis users compared with adolescent schizophrenics who have never used cannabis.
  • Suicide and violent death: a Swedish study found more suicides among cannabis users than those who used other ‘harder’ drugs, and often more violent deaths eg jumping from high buildings/bridges.
  • A ‘cannabis personality’ can develop: fixed opinions on things, with fixed answers to questions.  Struggling to express themselves, inability to take criticism, deflection and transference of blame for their own mistakes, planning for the immediate and long-term future becomes very difficult. They can become precociously independent (attempting ‘adult’ ventures when still immature).
  • Often young users put themselves in dangerous situations and at risk, this is because cannabis can adversely affect the area of the brain that keeps you safe, which develops after the area that can cause recklessness.
  • Violent mood swings, depression, stunted emotional maturity and loneliness are all common especially with young users.

If you are a parent or carer how do you know if your child or teen is using cannabis?’

It isn’t easy sometimes to live with teenagers under ‘normal circumstances’  The situation becomes even worse if they start to use drugs.

Lack of communication, arguments, secrecy and self-centredness can all be normal manifestations of moving into adulthood, so it isn’t always easy to tell if drugs are involved.

Think prevention: cannabis is the drug most young people begin with, and we know that its use can lead onto harder drugs, there is evidence it primes the brain for harder drugs, so preventing use is vital.

Follow your instincts. If you have a feeling that things are not as they should be, talk to your child and to the school. If your child is using cannabis (and the age of initiation is falling in the UK to around 10 – 13), your child is almost certainly getting supplies from another child at school.

Ask the school what their policy is on possession and dealing of the drug.

Be confident – the school is in ‘loco parentis’ and most children begin their addiction at school. You may be able to nip things in the bud. Ask to see the Headteacher, ask if they have noticed a problem and ask for support.

Get together with other parents – parent power works, remember you are the clients. Find out as much as you can about drugs to empower you (see our choice of web-sites and downloadable documents below).

Remember that cannabis is not the same as it was in the ‘hippy’ era; it is 2-3 times more powerful and potentially very dangerous to the mental health of the young. As one addict said to us

‘’Skunk’ may be Class C but it has a Class A effect.  I’ve tried just about everything but it was that stuff that I couldn’t handle, it completely messed with my head, it was awful!’ So there you have it – from the horse’s mouth.

Often users have little sense of consequences of their actions, and their behaviour begins to be very destructive to themselves and to those around them. This is a common, chilling hall-mark of cannabis use among the young.

Be aware that colluding with your young person over drugs is only going to help them slip into addiction more easily – be strong as early as you can.

SO WHAT TO LOOK OUT FOR? (all drugs)

  • A combination of changes in behaviour, physical appearance, emotional outbursts, money going missing, school grades dropping and new friends being substituted for old ones, (especially older ones) should all start to ring alarm bells.
  • Physically – complexion changes, lack of colour – a grey/green hue, dark eye bags, blank expression.
  • Dilated pupils are a physical sign that is pretty fool-proof for parents, and evidence of Optrex in bags and pockets is one to look out for. (Unlike heroin where pupils go smaller, cannabis causes pupils to grow bigger).
  • Sensitive eyes, runny nose, sores and burns on flesh, clothes, sheets.
  • Blood on sheets.
  • Burns around the mouth, rash around the mouth.
  • Continuous coughs and chest infections, sniffing.
  • Keeping arms covered.
  • Blackouts.
  • Cravings for sweet things.
  • Weight/appetite loss.
  • Tiredness.
  • Chain smoking.
  • Paranoia.
  • Radical changes in behaviour and personality,.
  • Unusual smell, odours on breath ad clothes.
  • Lying, treating the rest of the family with disrespect, continually challenging and even becoming verbally or physically violent.
  • Staying out for long periods with no explanation, secrecy as to where.
  • Stealing money, shoplifting or making secretive phone calls.
  • Lack of interest in the future, lacking in ambition, couldn’t care less attitude in a once conscientious child/teen.
  • ‘Baggies’ in pockets, (small plastic bags) with pungent, strange smelling residue or substance (usually green), large or small Rizla papers, bus-tickets/card torn in shape of a ‘roach’ (used to make a filter).
  • Items connected to drug taking include; matches, burn marks on clothes or furniture, plant seeds/stems, small cardboard tubes, silver foil, candles, blackened spoons, clothes with an unfamiliar or smoky smell, pipes, bongs.
  • Unpredictable eating and sleeping patterns, unkempt appearance and neglect of hygiene, speech slurred, infections, stomach upsets and cramps, indigestion.
  • School grades slipping, classes skipped, playing truant, teachers disobeyed and held in disrespect.
  • Never having money and being very antagonistic to any type of authority.
  • Mood swings are common, as are insensitivity and emotional outbursts. They find it difficult to concentrate and pay attention, so memory difficulties are common. Time is meaningless, inability to plan.


  • Do not be afraid of using ‘Tough Love’ techniques. Teenagers need to know who is in control, and need firm boundaries (even if it is to kick against!) but stay calm.
  • Present a united front – children can divide and rule.
  • Confrontation will almost certainly elicit denial, instead act in a calm, measured way. Psychologists advise naming what you believe is going on without being judgmental (remember that peer pressure is strong).
  • Try and time speaking to your child with when they are not stoned.
  • Confront with evidence if possible, but don’t blame: listen to what your child has to say – try and get them to talk about their feelings and what may be going on in their lives.
  • Talk to them about the fact that cannabis is illegal, what it may mean if they get a conviction (eg unlikely that a visa for the USA would be issued).
  • If you suspect that your teenager is smoking skunk, which has an overpoweringly pungent sweet/sour smell, the first step is to impose consistent boundaries.
  • Set house rules straight away – ensure everyone knows you live in a   a drug-free zone, preferably smoke-free, including the garden to avoid confusion.
  • Try to get a land-line number and address of where your child is staying overnight if they go on sleep-overs (no number, no sleep-over).
  • Check what your child’s friends’ families’ attitude to drugs is – discourage visits to homes where smoking is allowed or a blind eye is turned.  This can become increasingly important.
  • Talk to their friends’ families about your concerns, they may not be as up to speed, ignorance about skunk is common.
  • If your child doesn’t come home – go and get them. Be strong.
  • Impose sanctions – AHC – Actions have Consequences – grounding, removing privileges (internet, lap-tops, phones, guests to stay, allowances etc).
  • Seek help from your GP who may be able to refer you to a therapist, be firm.  (NB Family counsellors have usually not had drugs training) Get help from other agencies (see our Self Help and Support section of the site), such as DrugFam (0845 388 3853) or Families Anonymous (0845 120 660)
  • Get support for yourself and your partner (DrugFam or FamAnon can help with this) or sign up for our TAC local network and get talking/emailing with others in your area.
  • Find a good counsellor for yourself/your partner and get support that way – this is often a life-line and will help give you strength.
  • Don’t neglect other siblings/partners by giving the skunk user/addict too much attention.
  • A good tip is to ration the amount of time taken up by them – make an allotted time (say 15 minutes) where the problem is discussed or dealt with, then  move on.  This is highly recommended as addicts can become all-consuming to a household.
  • Prevention is better than cure – educate yourselves and the child about the effect of cannabis on the brain and biochemistry, teach younger children before they become tempted to experiment.
  • If all else fails and you feel you have to exclude your drug using off-spring, helping them to find alternative accommodation and being supportive financially at first, by paying for the first 3 months rent for example, until they find their feet, can help both parties with the transition. (Parents need to sleep at night!)
  • In severe cases, exclusion is sometimes the only way to protect other siblings, and to create a peaceful household where everyone can thrive (including parents).


The following sites have excellent information:

NIDA: (has a wealth of info on cannabis (marijuana) including Facts for Teens).

NDPA – lots of info on cannabis and the legalisation debate (your teen will have heard a lot about this issue and may challenge your values, you can arm yourself).

rad: – facts about cannabis, latest research from around the world, plus – (download ‘Cannabis – A cause for concern’ by Mary Brett)

Rethink:  – facts about cannabis.

Acknowledgements: with many thanks to Mrs M.D. Brett, Drug Education Adviser of TAC from 2007 – 2009, whose work has provided much of the scientific evidence for these pages, see  ‘Cannabis –a Cause for Concern’ (Eurad)

With thanks also to Kathy Gyngell for her blog ‘No need to be sanguine about Teenage Drug Abuse’ which supplied the figures on treatment.

References: Morgan et al (2009). Harms associated with psychoactive substances: findings of the UK National Drug Survey. Pharmacology.

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