Ensuring that people who have problems with drug misuse receive the help they need should be our priority, not catching them out by crudely applied drug testing, says Ian Hamilton

Linking cocaine use to violent crime is not a novel idea, but what is new is the suggestion that drug testing employees for cocaine use would lead to a reduction in knife crime. Shaun Bailey, the prospective mayoral candidate for London, grabbed headlines for making this policy announcement last month, also saying that he will publish a list of companies who return positive tests.

The justification for this invasion of privacy is the popular but unevidenced idea that middle class people using cocaine are funding criminal markets and are therefore responsible for an escalation in violent crime.The problem is that the underlying assumption is erroneous—there is no evidence to support a link between middle class cocaine use and knife crime in the UK. Shaun Bailey is not the first high profile person to make this assertion: Priti Patel, the home secretary, and Cressida Dick, the Metropolitan police commissioner, have done this too. Given the brief of Patel and Bailey, it is likely that they know this and their attempts to prod the consciousness of those using cocaine isn’t about facts, but a cynical attempt to appeal to voters.

The other aspect to this announcement that lacks evidence is the idea of workplace drug testing—at best, the evidence for it is lukewarm and could have unintended consequences. Given the rise and scale of cocaine use in the UK, some companies inevitably will have employees who have a problem with the drug. Not everyone who tries cocaine develops problems like dependency, but some will. Ensuring that they can receive the help and support they need must be the priority and not some crude attempt to catch them out by mandatory drug testing. 

However, unless these employees have access to private healthcare, accessing support will prove challenging as publicly funded specialist drug treatment is on its knees after years of budget cuts and outsourcing to the third sector. This situation seems unlikely to be reversed looking ahead at the inevitable further squeeze on public funding.

In terms of accuracy, mandatory drug testing also has its limits. While some employees may well be using drugs on a daily basis, others are likely to be using less frequently. Cocaine is one of the fastest metabolising illicit drugs, so the detection window is short. False negatives are likely to occur—particularly when an employee only uses cocaine outside of work but is only tested in work. Likewise, anyone using cannabis even occasionally runs the risk of returning a positive test due to the length of time metabolites can be detected, so occasional weekend use of cannabis could show up in a mid-week drug test. It is unlikely that employers will use the same standards of testing that athletes or footballers are subject to. This involves a chain of custody that ensures sportspeople (or their representatives) keep part of a sample that can be tested should they wish to contest the original test result. They will also use higher quality assays and collect samples in a timely way.

Yet apart from these technicalities, humans have proven to be ingenious in tampering or adulterating drug tests, particularly when sample collection is only partially supervised. After all, who wants the job of standing over a colleague while they urinate into a sample pot?

The more often senior figures repeat the misleading assertion that cocaine use is fuelling knife crime, the greater the risk that many members of the public will think it is true. Not only do these policies risk harming those who have problems with drugs, they do nothing to contribute to efforts to reduce knife crime. Both issues are serious and deserving of time, effort, and resources to tackle them. 

Yet shaming and stigmatising people has never been a successful way of resolving complex social issues like problem drug use or knife crime. Politicians know this yet are willing to use often vulnerable people to advance their own careers. If testing is to be introduced, then this should include breathalysing members of parliament before they vote—after all, firsthand experience is a useful way of enhancing empathy.

Ian Hamilton is an academic at the University of York with an interest in addiction and mental health. He previously worked as a mental health nurse with people who had combined mental health and substance use problems. Twitter: @ian_hamilton_

Competing interests: I am affiliated with Alcohol Research UK.