Also known as

Marijuana, Grass, Pot, Dope, Weed, Skunk, Hash, Joints, Spliffs, Smoke, Hydro, Green.


  • Cannabis is a naturally occurring substance, and is the most widely used illegal drug in the UK.
  • It contains a number of different chemical compounds (cannabinoids) – tetrahydrocannabinol (THC) and cannabidiol (CBD) are the most widely known. The effect of the drug will vary depending on the levels of these chemicals. “Skunk” tends to refer to a much stronger strain of cannabis which contains high levels of THC.
  • The desired effects of cannabis use include relaxation, euphoria, altered consciousness/distorted perceptions of time and space, increased awareness of sensation, increased libido, and increased appetite. Some people have found that cannabis can help reduce feelings of pain and/or nausea, which has led to its use as a medical treatment in some countries.
  • Unwanted effects include memory impairment, dry mouth, impaired motor skills, reddening of the eyes, anxiety/panic, paranoia, poor concentration, and loss of motivation.


  • Cannabis is a plant-based substance which can vary in appearance depending on which part of the plant is used, and how it has been prepared.
  • It is most commonly sold as a mixture of dried flowers and/or leaves, or small blocks of dried and pressed resin (a secreted gum) of the cannabis plant.
  • It can also be found as an oil, though this is less common in the UK.

Method of use

  • Cannabis tends to be smoked, most commonly mixed with tobacco in a hand-rolled cigarette (or “spliff”).
  • It can also be smoked in a pipe. Pipes containing water are often referred to as “bongs”, and they tend to intensify the effects of cannabis.
  • Cannabis can be mixed with food/drinks – for example, cakes, brownies, or tea. This can make it difficult to judge how much is being consumed as it takes a while for the effects to hit.
  • In recent years, “vaping” has increased in popularity and some cannabis users have learned to prepare it to be used in an e-cigarette.


  • Regular cannabis use can affect concentration and motivation. This can have a negative impact on performance at work or school/college, and can be detrimental to social relationships.
  • Cannabis can cause feelings of anxiety, suspicion, panic and paranoia.
  • In some cases, it has been linked to psychotic illness (including schizophrenia and similar conditions). Although the relationship between cannabis and psychosis is complex, in some people it does appear to increase the risk of becoming unwell and/or relapsing after a period of recovery.
  • Cannabis can have an impact on sleep quality. Although many users find it helps them to get to sleep, it impairs Rapid Eye Movement (REM) sleep, which leaves people feeling less rested than they would if they fell asleep naturally.
  • Smoking cannabis is associated with the same risks as smoking tobacco, ranging from sore throats and coughs to lung cancer and emphysema.
  • It can cause increased heart rate and blood pressure.
  • Frequent use of cannabis may affect fertility. It can cut a man’s sperm count and can suppress ovulation in women.
  • Cannabis impairs concentration, reaction times, and co-ordination. This is particularly noticeable when it is used with alcohol. People who are under the influence of cannabis are at greater risk of having an accident and hurting themselves. Driving after smoking is particularly dangerous.

Keeping safe

  • If you choose to use cannabis, then use them in a safe environment and in the company of someone you trust. Ideally, this person will not have used the substance themselves and will be in a position to get help if things go wrong.
  • The effects of cannabis can vary a lot depending on what strain you are using. Take a small amount first to test effects and strength, start low and go slow.
  • If you choose to eat or drink something containing cannabis, wait for a while before taking more. It can take a couple of hours to kick in, and you could end up taking a lot more than you intended.
  • It is safer to avoid mixing cannabis with alcohol as this can increase the effects of both substances.
  • It is illegal and very unsafe to drive if you are under the influence of cannabis. It can slow your reaction times and greatly increase the risk of an accident.
  • Try to avoid using cannabis every day, and aim to have at least a few drug-free days each week. Although cannabis may not be as physically addictive as drugs like heroin or alcohol, it is easy to build up a psychological dependence and regular users can notice withdrawal effects (e.g. insomnia, agitation. etc.) when they try to stop using. Regular cannabis use can also have an impact on motivation, which can cause difficulties with performance in work or school/college.
  • Cannabis can have a range of effects on mental health, including anxiety, paranoia, and even psychosis. Some people are more vulnerable than others to these effects – if you notice any troubling symptoms, stop using cannabis and consult your doctor if they don’t improve. If you have suffered from a psychotic illness, please use extra caution when deciding whether or not to use cannabis.

Legal status

  • Cannabis is a Class B drug – it’s illegal to have for yourself, give away or sell.
  • The penalty for possession of cannabis is up to five years imprisonment.
  • Supplying cannabis can result in a fourteen year prison sentence and an unlimited fine.
  • Like drinking and driving, driving when high is illegal – and you can still be unfit to drive the day after smoking cannabis. If you are caught driving under the influence, you could be fined, disqualified from driving, or receive a prison sentence.