Cannabis plants

Drug classification: should cannabis be legal?

Some laws around the world have been relaxed in recent years. Should using or dealing this drug remain illegal in the UK? By Emma Dixon

Cannabis has a long history of medical as well as recreational use in the UK. For example, Queen Victoria was prescribed it for pain relief in the 1890s.

It was first classified as a class B drug in the UK under the Misuse of Drugs Act in 1971, meaning that growing, producing, possessing or supplying it is illegal. It was reclassified as a class C drug in 2004, meaning you could no longer be arrested for possession, but returned to class B status in 2009 and remains illegal for both recreational and medical use.

What is cannabis?

Cannabis is a drug that comes from the plant Cannabis sativa. While it contains hundreds of chemicals, its main active chemical component is tetrahydrocannabinol (THC), which is responsible for most of the drug’s effects – including feeling chilled and happy, as well as the hallucinogenic properties.

It is taken in many forms: recreationally it is often smoked with tobacco, consumed in food, or inhaled using cannabis vaporisers. Aside from THC, cannabis also contains a compound called cannabidiol (CBD), thought to be responsible for the medicinal effects associated with the drug.

THC reaches the brain quickly, and binds to CB1 and CB2 receptors – part of the endocannabinoid system (see our article on the chemicals of the brain). THC is able to bind to these receptors because it mimics a natural neurotransmitter, anandamine – sometimes referred to as the ‘bliss’ molecule.

Anandamine is thought to be involved in pleasure and motivation, and can increase the production of dopamine in the brain. Unlike THC, anandamine is broken down quickly in the brain, so it can’t create the euphoric high associated with THC in cannabis. THC is more chemically robust, so lasts a lot longer in the brain, creating a prolonged high, as well as other effects.

These psychological effects depend on which areas of the brain are affected – if the nucleus accumbens is affected, the result is a high, but in other areas of the brain, THC may induce panic, impaired memory or increased appetite.

Medicinal uses

While cannabis’s medical potential has been noted for centuries, the biology behind it was only understood more recently. Unlike THC, CBD doesn’t appear to bind to CB1 and CB2 receptors, but may interact with ion channels in neurons and with enzymes. These interactions are thought to be responsible for the drug’s analgesic (pain-relieving) and anti-inflammatory effects, with some animal studies showing CBD to be hundreds of times more effective than aspirin.

Cannabis is legal for medical use in several European countries, Canada, and many states in the USA. It is used by patients for a wide range of conditions, including chronic pain, HIV/AIDS, cancer and epilepsy. Different strains of cannabis can be bred for high CBD levels (for best medicinal effects) and low THC (to minimise hallucinogenic effects).

In the UK, there is one cannabis-based medicine available. Sativex is an oral spray of THC and CBD extracts from cannabis plants, and is licensed for use by people with multiple sclerosis that hasn’t responded to other drugs. Legal restrictions mean that it can only be prescribed under guidance of a specialist, and passing the drug to someone else, or possessing it without prescription, is illegal.

One concern around legalising cannabis for medical use is that people might become dependent on it. However, research suggests only 9 per cent of users (of recreational and medicinal cannabis) will develop dependency – rising, however, to 17 per cent if use started at a younger age.

It has been suggested that cannabis-derived drugs may be a viable alternative to legal opiate-based medical drugs (such as morphine), which research suggests to be more addictive and carry a higher risk of death.

Recreational uses

Research into the medical benefits of cannabis may sound promising, but there are many dangers associated with the use of cannabis recreationally. Excessive use at high doses has been linked with a higher chance of developing psychoses (mental health disorders often causing distorted perception) and schizophrenic symptoms. This is likely in part caused by the increase in strength of ‘street’ strains in the last few decades.

Critics warn that promoting cannabis as a medical drug signals to young people that there are no adverse side-effects – and cannabis may be a particular danger for young people. People who use cannabis from a younger age are more likely to develop dependency (around half of cannabis addicts who seek rehabilitation are under the age of 24), and may be more vulnerable to cognitive impairment.

Researchers have looked at the effects of cannabis in rats. They have found structural changes in the rats’ brain linked to learning and memory deficits. These rats were also more likely to self-administer other drugs, including heroin, highlighting concerns that cannabis may act as a ‘gateway drug’.

Lead image:

M a n u e l/Flickr CC BY


Questions for discussion

  • Just because something is legal, does that make it safe? Can you think of two examples of legal things that you don't think are safe?
  • What are the arguments for keeping a substance like cannabis illegal in the UK?
  • What are the arguments for making a substance like cannabis legal, for medical or recreational use?
  • Who should decide whether a drug should be banned?

Further reading

About this resource

This resource was first published in ‘Addiction’ in September 2015.

Education levels:
16–19, Continuing professional development