The most commonly used psychedelics are currently illegal to supply and possess in the UK.

Supposedly, psychoactive substances are classified on the basis of harm, but the government's chief drug adviser was sacked when he pointed out that classical psychedelics are far less dangerous than alcohol. In reality, substances are banned on the basis of unsubstantiated health risks and tabloid hysteria as part of a peculiar moral crusade.

A 2005 report by the House of Commons Science and Technology Committee described the way substances are classified under the law as "arbitrary", "unscientific" and "based on historical assumptions, not scientific assessment". The report was especially critical of the classification of psilocybin mushrooms amongst the most dangerous and harmful substances.

Let's examine some key arguments for why psychedelics should be legal to supply and possess.

The benefit argument

Psychedelics bring about profound and meaningful experiences. In a 2011 study by the Johns Hopkins School of Medicine, 18 healthy adults participated in five eight-hour sessions with either psilocybin (the active ingredient in magic mushrooms) or a placebo. One month after sessions, 80% of those who received the substance said the experiment was one of the top five most meaningful experiences of their lives; 50% said it was the single most meaningful experience.

80% of the volunteers in that study, after having one or two high doses of psilocybin, reported that the experience was among the 5 most personally meaningful and spiritually significant experiences of their lives. In fact, about 50% said it was the single most personally and spiritually significant experience of their life, comparing it to the birth of a first-born child or death of a parent. These are stunning and remarkable findings.

Prof. Roland Griffiths, Johns Hopkins University School of Medicine

Many of the participants said they were left with the sense that they understood themselves and others better and therefore had greater compassion and patience. The participants themselves were not the only ones who saw the benefit from the insights they gained: their friends, family member and colleagues also reported that the psilocybin experience had made the participants calmer, happier and kinder.

This is not a new discovery. Psychedelics have been used by humans in spiritual and religious settings for tens of thousands of years (psychedelics are often called entheogens in this context). The profound shifts in worldview that psychedelics can bring about mean that they are now being investigated as a treatment for various conditions including depression, anxiety, addiction and PTSD.

People in the psychedelic trip often experience being at one with the world or even with the universe. It’s as if they’ve gone out to another place. They exist beyond their body. That experience can give them a sense of perpetuity, of permanence, of being part of the cycle of life, which of course we all are.

David Nutt, Professor of Neuropsychopharmacology, Imperial College London

There is strong anecdotal evidence that psychedelics improve creativity and problem-solving abilities. John Lennon attributed the Beatles' best-selling album Revolver to the group's use of LSD, whilst Apple's Steve Jobs said taking LSD was "one of the most important things [I did] in my life". By maintaining the ban on them, we're missing out on potential advances in healthcare, science, technology and philosophy.

Psychedelics, used responsibly and with proper caution, would be for psychiatry what the microscope is for biology or the telescope is for astronomy.

Stanislav Grof

The liberty argument

A 2010 study rated LSD and magic mushrooms as among the safest of 19 commonly used drugs, significantly safer than alcohol and tobacco.

Surely any psychoactive substance less risky than alcohol should be legally available in some way? Anything else is pure discrimination against sections of the population that happen to prefer other substances.

What possible justification is there for saying "OK, you can legally go out binge drinking every Friday and Saturday night, but if you go out picking for magic mushrooms once a year then we'll lock you up"?

The substitution argument

The use of psychoactive substances is a near universal practice of human cultures across history. Whatever the laws, people will still use psychoactive substances.

Were psychedelics and other low risk substances legalised, we would likely see a net health benefit to society as (at least some of the time) people chose to consume psychedelics instead of alcohol and other riskier substances. Prof David Nutt estimates that a regulated market in cannabis could cut alcohol consumption by up to 25%.