For decades it was cast as a harmful gateway drug to a lifestyle of feckless criminality. But the last few months has brought a momentous shift in the official position on cannabis following pressure from families who have used it to treat conditions like epilepsy.

Home secretary Sajid Javid has announced a review of the drug’s medical benefits and said it will be available on prescription this autumn.

Javid’s about turn came following pressure from Charlotte Caldwell, whose 12-year-old son Billy has autism and a rare form of severe epilepsy that saw him endure up to 100 seizures a day.

Pressure was also brought to bear by Hannah Deacon, whose son Alfie Dingley, six, suffered 150 seizures a month.

Both parents were eventually given licences by the Home Office to use cannabis for their children’s seizures.

Autumn has now arrived, but the official Home Office position suggests it’s still too early for patients to go to their GPs pleading for cannabis.

The Home Office say they are continuing to work with the Advisory Council on the Misuse of Drugs (ACMD) on the legal changes designed to help patients with “an exceptional clinical need”.

But in the meantime an expert panel has been set up to review decisions made by doctors trying to prescribe cannabis for patients before the law changes.

Parents and adults struggling with autism say though the government’s rethink is welcome, the focus on “exceptional clinical need” is too narrow.

The expert panel insists that the doctor shows “there is no other lawful medicinal product (whether licensed or not) that would meet the specific need of the patient”.

Trials and tribulations

Sharon Jenkins, 48, from Pembrokeshire, in west Wales, whose son Kieran, 22, has severe autism, epilepsy and a learning disability, believes this means she would have to trial her son on a whole range of drugs before cannabis.

Full-time carer Jenkins looks after Kieran (pictured above) with graphics design technician husband Tony (pictured top, with Sharon), 52, and trainee teacher daughter Talia, 24.

She has already tried her son on a cannabis oil containing only cannabidiol (CBD), which is the non-psychoactive substance found in the plant.

CBD-only cannabis oils are classed as food supplements and can be bought in UK health food stores.

But Jenkins wants the right to try her son on either whole-plant cannabis, or a medication derived from the herb that also contains tetrahydrocannabinol (THC), which is the hallucinogenic compound in the drug.

The cannabis oils used by Caldwell and Deacon to treat their children’s seizures contains THC.

THC and autism

Autism is strongly linked to epilepsy. Experts estimate between 20 per cent and 40 per cent of people with epilepsy also have autism.

Jenkins believes THC forms an important part of the plant’s ability to improve autism’s symptoms. She says her son suffers with the occasional seizure and problems with aggression that are not responding to licenced medications.

Jenkins maintains children and adults like her son will be missed by the government’s legal changes focused only on the most extreme cases.

Jenkins said: “As we know with Billy Caldwell and those children they’re having loads of seizures.

“For the children who are only having one, also what about then for the children or adults with challenging behaviour? What do you have to prove you’ve gone through for those?”

Internationally, there is a growing acceptance of cannabis as medicine.

In Israel and parts of the US families already treat autism with cannabis. Thirty-one US states have comprehensive medical cannabis programmes.

Also, recently approved efforts in a further 15 states allow use of "low THC, high CBD"  products for medical reasons in limited situations or as a legal defence.

Justin Clarke, 29, from Telford, in Shropshire, self-medicates using around £30 worth of street cannabis a month to treat his autism, depression, attention deficit hyperactivity disorder (ADHD), anxiety and irritable bowel syndrome (IBS).

Clarke, who spoke in Parliament on the benefits of cannabis, says it helps him regulate difficulties with sensory overload and manage anxiety.

Software tester Clarke, who was diagnosed with autism aged 23, also believes the government’s approach to cannabis is too restrictive.

Clarke, who is editor of the Facebook group Cannabis for Autism, said: “If you compare some of the side-effects of some of the medications they try before they try cannabis they are a lot more severe and there’s a lot more potential for them to go wrong.”

Clarke says he is aware of studies linking cannabis to mental health problems.

The Royal College of Psychiatrists (RCP) say there is “growing evidence” that people with serious mental illnesses, like depression and psychosis, are more likely to use cannabis.

In addition they say using the drug regularly appears to double the risk of developing a psychotic episode or long-term schizophrenia.

The RCP also maintains that there is a “clear link” to cannabis use and later mental health issues where someone has a genetic vulnerability.

Clarke says he carefully monitors his reaction to the drug and is happy with his response since he started using it in August 2017.

“I do keep logs of any negative things that I experience that I attribute to cannabis, but I haven’t really experienced anything that’s caused me any concern.”

As well as cannabis oils pharmaceutical cannabis products Sativex and Epidolex, both made in the UK, may be the first to be prescribed by GPs under the new licensing system.

Professor Mike Barnes, an expert in medicinal cannabis who secured Alfie’s license, said it’s still unclear how the government will define “exceptional need” or determine the conditions eligible for treatment.

Barnes suspects autism will not be included as the “evidence for efficacy is a bit sparse so far”.

Neurologist Barnes says this is a Catch-22 situation as if it is “not allowed how will we ever learn whether it is useful”.

The medic is hoping prescriptions will be allowed on a doctor’s discretion and says the picture should be clearer by the end of October or early November.

A Home Office spokesperson said Javid is carefully considering advice from the ACMD on “these important changes to the law”.

"He (Javid) will meet with Dr Owen Bowden-Jones, chair of the ACMD, to discuss this further and announce his decision in due course," added the spokesperson.