The medical use of cannabis – or marijuana – has been increasingly permitted for the relief of a variety of conditions. It has been prescribed for people with conditions such as multiple sclerosis, spinal injury, arthritis, epilepsy, cancer, insomnia and muscle spasms. The legalisation of cannabis for recreational use is also spreading in an increasing number of countries, and the permissive cannabis regime in the US state of Colorado (and more recently, California) has encouraged many investors to see cannabis as a promising “growth market” for future expansion. It would seem that the wind is set fair to open up a new era of permissive legislation towards the “pot” that many of us saw, back in the 1960s, as a harmless hippy recreation. There have been petitions to “legalise pot” ever since that decade, and it looks as though its legalisation is now steadily succeeding in the Western world. But in America, a new book called Tell Your Children: The Truth About Marijuana, Mental Illness and Violence, by Alex Berenson, puts a different complexion on this so-called harmless recreation. Berenson, a writer married to a psychiatrist specialising in the treatment of mentally ill criminals, began to notice that many of the disturbed, and sometimes violent, individuals that his wife treated had smoked pot all their lives. When he investigated further he found that it was an accepted norm in the psychiatric profession that many people with serious mental illnesses smoked a lot of cannabis. According to Dr Erik Messamore, a psychiatrist who specialises in neuropharmacology, the rise of marijuana use in the US (according to the New Yorker, it’s doubled in the past 20 years), has produced a concomitant rise in a brain disease similar to schizophrenia, producing delusions, paranoia and psychotic episodes. It has been well documented that cannabis – especially with high levels of the chemical known as THC – can trigger schizophrenia in people who may be vulnerable to the condition. (The most compelling account of this is Patrick and Henry Cockburn’s book, Henry’s Demons, describing how Henry developed schizophrenia triggered by smoking cannabis.) The writer Peter Hitchens has been subjected to fierce criticism over the years – even from those in authority, such as police chiefs – for noting the connection between recreational cannabis, violent crime and mental illness. Now it seems that Alex Berenson’s manifesto will bring more attention to the social and personal dangers of this opiate. Medical application under supervision is very different from the liberalisation of this opiate for recreational use, which would hardly be in the common good.