Professor David Nutt is a professor of neuropsychopharmacology, Imperial College London, chair of DrugScience.co.uk, and author of Drugs - Without the Hot Air. On Thursday 25 February he delivered the IPR Public lecture ‘Time to Put Science at the Heart of UK Drug and Alcohol Policy’ and here he blogs about the topic.

The Psychoactive Substances Act, given Royal Assent on 28 January 2016, has no intellectual basis and is arguably the worst piece of legislation in living memory. The ban on the sale of all substances that are "psychoactive" is supposedly designed to reduce the harms from so-called legal highs. Protagonists for this Bill, particularly the Centre for Social Justice, made the claim that deaths from legal highs increased rapidly to a peak of 97 in 2013. They have continued to disseminate this number despite knowing it to be false as demonstrated by King and Nutt in the Lancet in 2014. Most of the drugs in the 97 total are illegal, which raises the interesting question as to why anyone would think that banning more drugs would reduce use and harms? In fact this ban may do the opposite and increase harms as it will drive use underground to the black market.

The best estimates we have of deaths from legal highs in 2014 from UK experts such as John Ramsey is about five. Most deaths from recreational drug use (excluding alcohol that kills 22,000 per year) come from long-illegal substances such as heroin and other opiates (around 1,200) cocaine (around 200) and amphetamines (around 60). So why the hysteria around legal highs, particularly drugs such as nitrous oxide than in its 200 year history hasn't killed anyone? One reason for this seems to relate to the rise of the "head shop" in many town centres. These are viewed like sex shops as lowering the tone of localities and increasing public disorder (though never to the extent seen with premises selling alcohol). Another aspect is the opportunistic vilification of youth culture by the right-wing media who have labelled nitrous oxide as "hippy crack", even though everyone knows it is very much less harmful than crack cocaine and no self-respecting hippy would be seen using it!

I would argue that the rise of head shops has in fact contributed to this low number of deaths from legal highs. The head shop owners usually test out their products on themselves and only sell those that they know to be enjoyable and safe. Some legal highs such as methiopropamine (aka pink panther/bubbles/sparkle) have been sold for many years by head shops. Estimates suggest as many as one million doses a month are consumed in the UK with no known deaths directly attributable. Like all shopkeepers, head shop owners want customers to return rather than end up in the mortuary. Moreover if they are leading to public disorder then local authorities have already demonstrated these shops can be shut down under trading standards regulations.

This law was supposedly based on the Irish one which did close head shops but sadly led to an increase in deaths, as predicted when a market is driven underground or into the internet so all semblance of quality control is lost. Also dealers of illegal drugs have a strong incentive to sell highly addictive high profit ones such as heroin and cocaine rather than the safer and less-addictive legal high type of stimulants.

The Act is therefore unnecessary and the penalties disproportionate to the real harms of legal highs. It also impedes medical and neuroscience research. By banning safe legal highs it moves the law from one that reduces harm to one that tries to control moral behaviour. I would argue this is the worst assault on personal freedom since the 1559 Supremacy Act decreed that the practice of Catholic beliefs was illegal. It should not have been allowed to come into law.

Follow Professor David Nutt on Twitter: www.twitter.com/ProfDavidNutt

Listen to Professor Nutt's lecture as a Podcast: https://soundcloud.com/uniofbath/time-to-put-science-at-the-heart-of-uk-drug-and-alcohol-policy