You’re effectively using the essential ingredients of cannabis right now. You and everyone else. That’s because our brains, and other parts of the body, have a natural endocannabinoid system that is now known to assist with how we deal with pain, the control of movement, the protection of the brain after damage and a host of other functions. Our increasing knowledge of this natural endocannabinoid system now gives a solid scientific rationale for why cannabis has so many positive medicinal effects. And as well as this recently understood scientific rationale, there is a substantial body of clinical evidence that medical cannabis works. My review of that evidence is published today by the UK all-party parliamentary group on drug reform as part of their inquiry into medical cannabis.

My challenge to the government is to have the political courage to accept the scientific rationale, accept the evidence and move to legalise access to medical cannabis under prescription here in the UK as a matter of urgency.

Cannabis has been a useful medicine for centuries, with known use dating back to 4000BC in ancient China

Currently, the government has cannabis classified as a Schedule 1 drug, a classification for substances judged to have no medicinal value. This is irrational and incoherent. The evidence is plain to see and has been compelling enough for a large number of countries to legalise access to medical cannabis including the Netherlands, Germany, Spain and 25 US states.

My report shows that there is strong evidence that medical cannabis helps with chronic pain; spasticity (common, disabling and painful after stroke or brain injury and common in those suffering from multiple sclerosis, as examples); for nausea and vomiting, especially during chemotherapy; and for the management of anxiety. There is also evidence of usefulness in sleep disorders, for appetite stimulation (in HIV, for example), fibromyalgia, post-traumatic stress disorder, severe childhood epilepsies, bladder problems and even for control of some cancers. The list goes on.

And this issue matters to a lot of people. Estimates by the campaign group End Our Pain put the number of people in the UK taking cannabis primarily for medical reasons at one million. Many have found that “regular” prescription medicines just don’t work for them, or have debilitating side-effects. As access to cannabis in the UK is illegal, all these people are at risk of prosecution. These people would be regarded as patients in those countries with a more enlightened approach, but here they risk being treated as criminals.

The usefulness of medical cannabis is unquestionable; but is it safe? Certainly there are some potential short-term effects such as dizziness, drowsiness, dry mouth, balance problems and sometimes confusion. These effects, however, are largely induced by the psychoactive component – tetrahydrocannabinol (THC). This is the chemical that causes the “high” sought by recreational users. The other main chemical is cannabidiol (CBD), which is neither illegal nor psychoactive and indeed counters the effects of THC. That’s why medical cannabis will be produced in controlled conditions to ensure the right balance between CBD and THC.

Much more powerful and potentially dangerous prescription medicines are prescribed routinely by doctors. Every drug prescribed has positive and negative effects and the doctor’s job is to weigh those risks and benefits, explain that balance to the patient and allow an informed choice. It would be no different in the case of medical cannabis.

What about the threat of long-term problems, such as triggering schizophrenia? The evidence is conflicting but nevertheless some cannabis products (mainly those high in THC) can induce transient symptoms similar to the symptoms of schizophrenia and exacerbate symptoms in individuals already suffering from psychosis. I would expect a doctor not to prescribe medical cannabis in such cases.

Cannabis has been a useful medicine for centuries, with known use dating back to 4000BC in ancient China. It was also widely used in ancient Indian, Greek and Roman cultures. Medicinal use was first properly documented by Dioscorides in the first century AD. It has certainly gone through periods of being in and out of fashion. A particular period of enthusiasm was during the 19th century when, for example, Sir John Russell Reynolds recommended it for period pain suffered by Queen Victoria.

The government now has the scientific rationale and the evidence. And through the campaigning efforts of End Our Pain and others, we have the powerful personal testimonies of those that are suffering. Let’s act. Let’s legalise access to medical cannabis now.