What is cannabis oil and how does it help treat epilepsy?

Cannabis oil is used by sufferers of epilepsy, multiple sclerosis and cancer and is widely credited with various medical benefits.

Debate over its use has ignited following the high-profile case of severely epileptic 12-year-old Billy Caldwell, who had his supply confiscated by the Home Office before it was returned.

1. What is cannabis oil?

It is produced by using steam distillation to extract active substances from cannabis plants and is typically consumed orally.

Its effects come from two cannabinoids found in the marijuana plant: Tetrahydrocannabinol (THC) and cannabidiol (CBD).

A low concentration version is available to buy over the counter in the UK - provided it contains less than 0.0.5% THC.

2. Is it legal?

The oil is illegal in Britain despite being available elsewhere - but the law on its use is currently being reviewed.

3. What makes it illegal?

THC is a psychoactive ingredient which produces the classic mind-altering effects of cannabis use, making users feel "high".

It is the compound associated with the "stoner" image and has been banned over fears it can raise the risk of psychotic illnesses and its potential for addiction.

The risk of harm from cannabis is higher if you use regularly from a young age, as your brain is growing and still forming connections, according to the NHS.

4. Are any cannabis products legal in the UK?

There are two prescription drugs which use cannabinoids available in the UK.

Sativex uses CBD and THC to relieve the pain of muscle spasms in multiple sclerosis.

While Nabilone is sometimes used to relieve sickness in people having chemotherapy for cancer.

5. Does cannabis have medicinal benefits?

The anecdotal evidence is widespread but it remains a heated topic of division among doctors, scientists, policy-makers and the public given the history surrounding its use and the legacy of the "war on drugs".

Cannabis can help with problems like appetite loss and relief of nausea during chemotherapy, for example.

It is also widely used as an anti-inflammatory to manage chronic pain, such as with arthritis and rheumatism, and is often preferred to conventional painkillers.

Trials of cannabis-based drugs are ongoing in the UK for a host of medical conditions.

The NHS states: "We won't know whether these treatments are effective until the trials have finished."

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