What is cannabis? | Methods of use | Dose and Price | Effects/Risks | Therapeutic use | Legal status | Legalisation | Prevalence | A gateway drug?

What is cannabis?

Bhang, black, blast, blow, blunts, Bob Hope, bush, dope, bud, draw, ganja, grass, hash, hashish, hemp, herb, marijuana, mary jane, pot, puff, Northern Lights, resin, sensi, sensemilla, skunk, smoke, spliff, wacky backy, weed, zero etc.

Cannabis is a drug derived from a bushy plant found wild in most parts of the world and easily cultivated in Britain. There are three varieties of the plant, Cannabis sativaCannabis indica and Cannabis ruderalis. In Western countries it is generally used as a relaxant and mild intoxicant.

cannabisThe most important psychoactive ingredients in cannabis are the tetrahydrocannabinols (THC).

Types of cannabis

Cannabis comes in different forms:

Herbal/grass/weed/marijuana – This is the most common way to find cannabis.  It is composed of the dried leaves and flowering parts of the female cannabis plant and resembles compressed dried herbs. 

Skunk – Skunk is a strong form of herbal cannabis that consists just of the buds. Much of the cannabis in use in the UK is homegrown either under grow lights or in greenhouse conditions using ‘hydroponic’ techniques (ie, growing plants in nutrient-rich liquids rather than in soil). This produces a stronger, more potent form of the drug which is sometimes referred to as Skunk.  In fact skunk is only one of 100 or so varieties of cannabis plant which have high levels of tetrahydrocannabinol (THC).

Hash or cannabis resin – A black or brown lump. Not seen in the UK very much anymore.

Cannabis oil – Rarely seen, cannabis oil is a sticky, thick yellowy/brown liquid.

Shatter – Highly concentrated form made by stripping the THC out of the cannabis plant with Butane gas, the result is a glass-like extract. It is broken up to be smoked and can be used in e-liquids in vape pens.

Methods of use

Smoking – Probably the most common way to use herbal cannabis is to roll it up in a cigarette (joint or spliff) and smoke it. Sometimes tobacco is included in the spliff.

Inhaling – Sometimes cannabis may be inhaled via a pipe or bong. There have recently been reports of e-cigarettes being used to smoke cannabis – either by using specialised cannabis ‘vapers’ or by turning the cannabis into a liquid which can be used with a normal e-cigarette.

Eating/drinking – Cannabis may be baked into cookies or brownies, mixed with alcohol or brewed into a tea.

When eaten the effects take longer to start but often last longer too. Eating cannabis may result in a large dose being taken in one go, making it difficult to avoid unpleasant reactions.

Dose and price

Regular users might consume one-eighth of an ounce per week. Heavy and regular cannabis users might use that amount in a day. Roughly one-sixteenth of an ounce of cannabis resin would be sufficient to produce four strong joints.

For one ounce, hash costs £80-£150 and herbal cannabis costs £160-£180. 1g of resin could cost between £70 and £100. The cost for cannabis varies between areas of the UK and, out of 7 cities surveyed in Seedo’s 2018 cannabis price index, London came out the most expensive for cannabis in the UK.


Using cannabis causes a number of physical effects including increased pulse rate, decreased blood pressure, bloodshot eyes, increased appetite, tiredness and occasionally, dizziness.

These effects can start within a few minutes and may last several hours depending on how much is taken.

While the effects of use rely on dose and the expectations and mood of the user, cannabis can often lead to a state of relaxation, talkativeness and the giggles. There is also a greater appreciation of sensory experiences such as music and hallucinations may occur with higher doses. It can be taken to enhance or detract from the effects of other drugs such as ecstasy or cocaine, particularly after long dance sessions.

While intoxicated, cannabis can affect the short-term memory, concentration, and intellectual or manual dexterity, including driving. Higher doses can lead to perceptual distortion, forgetfulness and confusion of thought processes. Temporary psychological distress and confusion can occur, particularly among inexperienced users or if the user is feeling anxious or depressed.

The physical effects of inhaling and smoking cannabis can impact on the respiratory system, leading to oral, throat, and lung cancer.

Psychologically, use of cannabis has been reported to cause anxiety and paranoia in some users and studies have suggested that it can be a trigger for underlying mental health problems.

While cannabis does not produce physical dependence, mild withdrawal symptoms have been observed in experiments.

Skunk’s strength and speed can sometimes catch out inexperienced users. Many report that the ‘stoned’ effect can come on rapidly and be disabling. The results can be quite dramatic, including anxiety attacks. Some of the more common effects include:

  • elation
  • profound relaxation
  • alteration of time and perception
  • transient hallucinations, rarely in the same league as LSD, uncontrollable laughing, increased sociability and talkativeness
  • nervousness, anxiety and mild paranoia
  • the ‘munchies’ – a strong desire to eat and continue eating.

Therapeutic use

Cannabis-based products for medicinal use in humans are in Schedule 2 of the Misuse of Drugs Act.

There is growing evidence that cannabis may be effective in providing symptomatic relief for diseases of the muscular-skeletal system like multiple sclerosis. It has also been reported as useful as an anti-nausea drug in chemotherapy, and to relieve intra-ocular pressure in glaucoma patients. Research is looking at a cannabis based mouth spray (Sativex) and if it can help treat glioblastoma after promising results in a phase 1 trial. And further clinical trials are underway exploring if cannabis based drugs can aid appetite loss in people with HIV or AIDS, and epilepsy in children. 

Following the high profile case of 12 year old, Billy Caldwell, who suffers from severe epilepsy that has been relieved by the use of cannabis oil, the Government announced in June 2018the granting of licenses for medical use and a review of the scheduling of cannabis. And on 11th October 2018 the Government announced that medicinal cannabis is now legal. Specialist doctors in the UK have been able to prescribe medical cannabis since 1 November 2018. Since the change in regulations there has been an increase in the prescribing of CBD products, but no increase in NHS prescriptions of THC-containing products (Barriers to accessing cannabis-based products for medicinal use on NHS prescription, 2019). In the two years following legalisation, the number of patients who have received NHS prescriptions for licensed cannabis medicines is estimated to be in the low hundreds. Conversely, medical cannabis prescriptions being issued privately in the UK are currently estimated at around 2500 and rising according to the 2021 Prescriber article “An update on medical cannabis prescribing in the UK”.

In recent years certain parts of the United States, including California, have issued licenses for the medical consumption of the drug.

A government report published in July 2019 reveals that parent’s expectations of the availability of therapeutic cannabis are being unfairly raised and that more research needs to be done to determine which patients could benefit – See: Drugs policy: medicinal cannabis, 2019.

See also:

Barriers to accessing cannabis-based products for medicinal use on NHS prescription Findings and Recommendations, 2019, (PDF)
This review was aimed at addressing the following question: Where they exist, what are the barriers to patients accessing cannabis-based products for medicinal use within the NHS where they are clinically appropriate for the patient, and how might these barriers be overcome? | NHS England and NHS Improvement, UK

Cannabis-based medicinal products, 2019
This guideline covers prescribing of cannabis-based medicinal products for people with intractable nausea and vomiting, chronic pain, spasticity and severe treatment-resistant epilepsy | NICE, UK

Cannabis is controlled as a class B drug under the Misuse of Drugs Act.

This means it is illegal to cultivate, produce, supply or possess the drug, except in accordance with a Home Office licence issued for research or other special purposes.

The maximum sentence for possession is 5 years and a fine or both. For possession with intent to supply the maximum sentence is 14 years or a fine or both. This is also the maximum sentence for production and cultivation.

It is also an offence to allow premises to be used for producing, supplying or smoking cannabis. This last type of offence – allowing the use of a drug – applies only to permitting the smoking of cannabis or opium.

Skunk, like most forms of cannabis, is a Class B drug under the Misuse of Drugs Act. Indoor growing systems may be detectable by police helicopters using thermal imaging equipment, while high intensity lights cause unusually large electricity bills. Anyone using a hydroponic system, or growing more than a handful of plants, is likely to be charged with intent to supply, as well as production and possession. If convicted, even small-scale growers commonly face one to two years’ imprisonment, while commercial growers may face longer sentences.

It is rare for maximum sentences to be given and guidelines put out by ACPO (Association of Chief Police Officers) advise police to take an escalating approach to those over 17 possessing cannabis for personal use, with a warning given the first time a person is caught and an on-the-spot fine for a second offence. If an individual is caught three times in possession of cannabis they may be arrested.

Cannabis warnings could be issued to adults from 2004, while khat warnings could be issued to adults from June 2014. The number of cannabis and khat warnings issued each year is in decline, according to the Ministry of Justice 2020 statistics, in a 12 month period the warnings issued went from 35,000 in 2016 to 17,800 in 2020, and in 2021 there was a further 4.1% decrease with 17,000 warnings issued. 

However on 11th October 2018 the Government announced that medicinal cannabis is legal and that patients can be prescribed medicinal cannabis by specialist doctors from 1 November 2018.

For more information on cannabis and the law please see the Release website


There are many calls to legalise cannabis in the UK including from Nick Clegg, formerDeputy Prime Minister who wanted to see a shift from punishment to treatment.

A 2018 YouGov survey revealed the general public is divided with 43% of respondents in support legalisation and 41% opposing it. The remaining 15% don’t know.

While the UK government has no plans to legalise recreational use of the drug, some countries have decriminalised it, allowing the personal possession of small amounts for personal use.

Many countries have legalised cannabis now including Canada, Mexico, South Africa and Uruguay. US federal reform is also imminent. For the legal status of cannabis in countries world-wide see the legality of cannabis Wikipedia page.


According to a report from the Office of National Statistics, Drug misuse in England and Wales: year ending June 2022, cannabis has consistently been the most used drug in England and Wales since estimates began in the year ending December 1995. In the latest year, 7.4% and 16.2% of adults aged 16 to 59 years and 16 to 24 years, respectively, reported having used the drug in the last year; a similar level to the year ending March 2020 and the year ending March 2012; however, levels are much lower compared with the year ending December 1995.

Cannabis is the most used drug in the world, the UNODC World Drug Report 2023 found that in 2021 there were an estimated 219 million users (4.3% of the global adult population) worldwide and that 1 in every 17 people aged 15–64 in the world had used a drug in the past 12 months.

Cannabis is also the most used drug in Europe, with the European Drug Report 2023 estimating 22.6 million people aged 15 to 64 (around 8% of European adults) have used cannabis in the last year. 

A gateway drug?

It is often suggested the taking of one drug, particularly cannabis, may lead to the use of other drugs. While it is true that most people who use heroin will have previously used cannabis, they are also likely to have smoked tobacco and consumed alcohol. Only a small proportion of those who try cannabis go on to use heroin. Importantly, though, cannabis use involves people in the buying of illegal drugs, making it more likely that they will meet with an offer of other drugs. In this example, it would be the illegality of cannabis use rather than cannabis use itself that leads most directly to contact with heroin.

Updated July 2023

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