Cannabis use disorder: effects, dependence, withdrawal and getting help in the UK

Cannabis is a plant-based drug that can be smoked, eaten or vaped. FRANK lists weed, skunk, hash, cannabis oil and highly concentrated forms such as dab or shatter. Cannabis contains many compounds, mainly THC, the main psychoactive compound responsible for the hallucinogenic effects, and CBD, which it says is thought to balance out some of the effects of THC and make users less likely to feel anxious and paranoid. Strong cannabis such as skunk has high THC and little or no CBD.

Cannabis use disorder is the clinical term for use that has become a problem: strong cravings, using more than intended, difficulty stopping and continuing despite harm. It exists on a spectrum and many people recognise features in themselves long before they would call it addiction.

FRANK explains that cannabis affects people very differently. Some feel chilled out, happy or giggly; others feel lethargic, unmotivated, paranoid, confused and anxious. How it feels depends on the person, their mood, the setting, the THC and CBD content, how much is used and how often. It can affect judgement and concentration, and FRANK says studies suggest it affects the part of the brain used for learning and remembering, with regular use by young people linked to poor exam results.

Physically, smoking cannabis can make you wheeze, cough and feel out of breath, and can make asthma worse. FRANK says it is likely to carry many of the long-term risks of smoking tobacco, including lung cancer, and that it can increase heart rate and affect blood pressure, which makes it particularly harmful for people with heart disease. It adds that smoking cannabis while pregnant can increase the risk of a baby being born smaller than expected.

FRANK says using cannabis can affect motivation, impair memory, cause mood swings, disturb sleep and make you depressed, anxious, panicky or even aggressive, and can make you see or hear things that are not there. Hours or days of anxiety, paranoia and hallucinations can follow, which only settle down if the person stops and sometimes do not settle at all.

It also warns that cannabis can cause a serious relapse for people with psychotic illnesses like schizophrenia, and can increase the chances of developing illnesses like schizophrenia, especially if you have a family background of mental illness and start smoking as a teenager. Anyone with distressing paranoia, hallucinations or a drop in mood after cannabis should see a GP promptly, and call 999 or go to A&E if there is a risk to life.

FRANK says that yes, you can get addicted: heavy cannabis users often get cravings and find it hard not to take the drug even when they know it is causing problems. When heavy users try to stop they can feel moody and irritable, feel sick, find it hard to sleep, find it hard to eat, sweat and shake and get diarrhoea. It adds that people who roll cannabis with tobacco also risk becoming addicted, or staying addicted, to nicotine.

Withdrawal can be unpleasant enough to drive relapse. Planning for sleep difficulties, irritability and low appetite, having support from friends or a service, and avoiding triggers can help. If low mood or anxiety is severe or you have thoughts of harming yourself, seek help urgently.

The NHS says that if you need help for a drug problem you are entitled to treatment in the same way as anyone else with a health problem. A GP may be a good place to start and will usually refer you to your local drug service; you can also approach a local drug treatment service yourself, and FRANK helps you find support near you.

At your first appointment staff will ask about your drug use, work, family and housing situation, may ask for a urine or saliva sample, talk through treatment options and agree a plan with you. You will be given a keyworker. The NHS lists talking therapies such as CBT, self-help programmes such as Narcotics Anonymous or SMART Recovery, and measures to reduce harm.

FRANK says driving when stoned or high can double your chances of a serious, or even fatal, car crash. It notes that cannabis is a Class B drug in the UK, with the exception of medical cannabis products legally prescribed by specialist doctors for specific health problems. This page does not cover medical cannabis, which is a separate prescribing pathway.

The NHS says charities and the NHS provide most drug treatment, with private drug and alcohol treatment organisations also available for those who are willing to pay. Local NHS-commissioned services are free at the point of use. Whichever route you choose, keeping your GP informed helps them monitor mental health, which is often the most important part of recovery from heavy cannabis use.