A photo of HM Prison Wormwood Scrubs taken from outside

Outlawing drugs once known as ‘legal highs’ led to waves of violence, self-harm and suicide in prisons, according to a study released by the University of Sussex.  

Despite being made illegal in 2016 New Psychoactive Substances (NPS) remain widely available behind bars, including Spice, a highly potent synthetic drug linked to unpredictable behaviour, stimulants such as mephedrone and the ketamine-like psychedelic methoxetamine. Today’s analysis of Ministry of Justice (MoJ) records from all prisons in England and Wales reveals major unintended consequences to the ban. The study found that while it reduced NPS availability, with an average fall of 32 per cent, outlawing the drugs also led to a surge in violence. There was a 38% rise in serious assaults, with 164 additional incidents in the four months immediately following the law change. The analysis found no reduction in the volume or severity of violence over the long term. 

Prison records also show a 15 per cent increase in self-directed violence in the weeks following the legislation, amounting to around 945 additional incidents of self-harm and ten suicides. Researchers believe higher prices made NPS drug habits unsustainable for some people with severe addiction, leading inmates to hurt themselves and clash with others.

Report author Dr Rocco d’Este, Associate Professor at the University of Sussex said: “Reducing the supply of any popular drug tends to inflate prices, and New Psychoactive Substances are no exception. With more money to be made from dealing and fewer inmates able to feed their habit, power struggles can break out among dealers and increasingly desperate addicts. This has inflamed an already heated environment in overcrowded prisons where mental health problems are highly concentrated.” 

Speaking to The Guardian back in 2016 the Chief Inspector of Prisons Peter Clarke warned of the worst drug-related problems ever seen in prisons, with “debt, bullying and violence… making it difficult for normal prison life to continue”. The Psychoactive Substances Act outlawed these drugs that same year, but until now little has been known about whether the ban succeeded. 

The report calls for policymakers to consider the links between withdrawal symptoms and violence when drawing up new drugs policies which will affect prisoners. Dr d’Este said: “Addicts withdrawing from synthetic cannabis can experience acute psychosis, hallucinations and paranoid delusions. Cutting drug supply in prisons where NPS addiction is rife without offering effective treatment adds another element of danger to understaffed institutions. We need to start addressing demand as well as supply by delivering proper medical treatment and improving living conditions for inmates.” 

Huge profits are being made from NPS sales behind bars. The report cites previous research by Manchester Metropolitan University showing that before the 2016 ban an ounce of synthetic cannabis could be bought online for as little as £84, or £3 per gram. This was resold in prisons for around £100 per gram, with inmates using contraband phones and mobile banking to transfer drug money. Various studies, including the Home Office’s own 2018 policy impact report, estimate that the ban increased NPS prices by somewhere between 80 and 300 per cent, as sources moved from legal head shops to the black market.  

Today’s paper uses MoJ records to compare incidences of violence and self-harm before and after the 2016 policy, covering 96 prisons over forty months. The researchers ruled out other explanations for changes in violent behaviour by creating a control group of prisons with a less serious NPS problem. The immediate rise in violence which was found in prisons with high rates of NPS use when the ban came in was not seen in the control group.

The University of Sussex’s report warns of future costs to society if authorities fail to act, citing 2022 research which found that violent prison conditions increase reoffending rates. Dr d’Este says: “Continuing to ignore the addiction and violence endemic to our prisons will lead to more crime on our streets, and more taxpayer money going on prison sentences in future. We need effective prisoner rehabilitation programmes that will also protect citizens and stop pretending we can just lock people up and release them back into society in a worse state than they went in.”