Are sleeping pills really lethal?

Millions of worried people who use sleeping pills for insomnia have a new anxiety to keep them awake at night. Their pills may kill them. In fact, they may be as dangerous as cigarettes. The headlines in yesterday's newspapers make ghastly reading for people who take sleeping pills and tranquillisers - particularly if, like many consumers of these anti-anxiety drugs, they are already hypochondriacs.

A study published in the British Medical Journal Open found that anyone taking sleeping pills twice a month is four times more likely to die in the next two and a half years than someone taking none at all. People taking high doses of temazepam, one of the benzodiazepine family of drugs, were six times more likely to die. Given that temazepam was dispensed 2.8 million times in England in 2010, that's scary. But it gets worse. Overall, people taking more then 132 pills a year suffered a 35 per cent increase in cancer. Also, heavy users of zolpidem, one of the drugs in a newer (and supposedly less addictive) category of sleeping pills and tranquillisers, were nearly six times more likely to die in the near future.

Zolpidem is one of the "Z-drugs" handed out in enormous quantities by GPs. Zopiclone, the best known, was prescribed 5.3 million times in England in 2010. We don't have separate mortality figures for it, but given that it's chemically so similar to zolpidem, the news is unlikely to be good. There are the makings of a health panic on both sides of the Atlantic. Although the study was published by the BMJ, it was carried out by American scientists and based on mortality rates in Pennsylvania. Its concluding section opens with the chilling sentence: "Rough order-of-magnitude estimates at the end of the supplemental files suggest that in 2010, hypnotics may have been associated with 320,000 to 507,000 excess deaths in the US alone."

Half a million deaths? The implication - if you only skim the news stories - is that there are unidentified killers lurking in bathroom cabinets all over Britain and America.

And the study's authors don't exactly reassure people taking sleeping pills when they suggest that a randomised test of these drugs - that is, putting people on them deliberately to see what effect they have - would be about as ethical as hooking them on cigarettes or throwing them out of planes without a parachute. At which point, patients on these drugs need to take a deep breath and relax (preferably without reaching for the pill bottle).

Let's start with an obvious question. If sleeping pills and tranquillisers were causing the deaths of between a third and half a million Americans every year, don't you think we would have noticed? As Malcolm Lader, professor of clinical psychopharmacology at King's College London, said yesterday: "I agree that these drugs do have problems but I find some of these results quite difficult to accept. The main one is that with 18 doses a year you have three times the mortality - that's quite incredible because you would have people dropping like flies."

It's a puzzle, this study. The scale is impressive: 10,529 patients on sleeping pills matched to 23,676 people not taking them. Data were adjusted for age, gender, smoking, body mass index, ethnicity, marital status, alcohol use and prior cancer. So that means we can't dismiss the findings by saying that the pill-poppers were disproportionately old, smokers, drinkers, divorced, etc.

But there's also no proof - none at all - that these drugs caused the heart disease, cancer or whatever illness from which their consumers died at an unusual rate. There's no biological trail. Perhaps some of the dead people killed themselves because the pills made them depressed, or had car accidents because they were spaced out - but that hardly explains the dramatic increase in mortality.

The consensus among health professionals yesterday was that there is something about people who take sleeping pills that makes them likely to die earlier - but it's almost certainly a complex combination of factors. If they need pills to sleep, that might indicate an underlying anxiety caused by physical ill health. Alternatively, the anxiety itself could be eroding the body's defences, causing any number of symptoms that can shorten your lifespan in subtle ways. But that's guesswork.

What isn't speculation is the fact that doctors in Britain and America still prescribe truckloads of these drugs to people who then become hooked on them. And, however you interpret the new study, it is further evidence that they are associated with bad health. I have been researching the use and abuse of prescription drugs for my forthcoming book about addiction, The Fix. One thing quickly became clear. Our national weakness for benzos and Z-drugs has taken many people way beyond the occasional short-term use envisaged by GPs.

Let's clear up one area of confusion. "Sleeping pill" and "tranquilliser" are words that describe how a drug is used; they're not radically different substances. A benzodiazepine such as diazepam - Valium - can be used for either purpose. Like all the benzos, it suppresses the central nervous system. "I take Valium either just before I go to bed or just before I step into the studio," says one broadcaster. "And no, it doesn't make me drowsy on air. It just banishes the butterflies."

Other benzos act faster than diazepam and do induce greater drowsiness; they're more likely to be used only at night. But in the course of my research I don't think I came across one sleeping pill that wasn't also being used recreationally.

"Valium and zopiclone are very popular at rock festivals," says Alice, 23, who works in publishing. "People want to come down and chill out after taking uppers. It's absolutely normal." And where do the pills come from? "Oh, somebody's GP. Or through the internet from Thailand."

The rise of internet pharmacies has helped to popularise tranquillisers among young drug-takers from all social classes. On the streets of the north-east of England, Z-drug pills circulate in strengths that are unavailable in the UK - evidence that they have been ordered online.

Meanwhile, GPs have to make sensitive judgments about drugs that patients are notoriously reluctant to come off, even though they're only really effective in the short term. "Doctors come under a lot of patient pressure to prescribe benzodiazepines," says Dr Robert Weeks, a GP in Market Rasen, Lincs, who has worked on a pilot scheme to reduce dependence on sleeping pills. "These things do work in the short term, but once people start using them as long-term social crutches, they do no good at all. Our best decision was to take everyone off repeat prescriptions for them, so they had to be renewed fortnightly. That gave us the chance to explain to patients that there are lots of practical steps they can take to improve the quality of their sleep without medication."

For dedicated pill-poppers, however, natural ways of chilling out are a poor substitute for the chemical buzz of a benzo - even if they have to keep raising the dose in order to get to sleep and enjoy "the floaty feeling before you drift off", as one enthusiast puts it. They will shrug off this week's headlines, just as they ignore the health warnings attached to any other substance that gives them a lift.

More worrying is the possibility that some people who have been innocently using benzodiazepine sleeping pills for years will be panicked into suddenly stopping. Which brings us to perhaps the single most important thing that potential users should know about these drugs - a medical fact infinitely better established than their association with dying early.

Coming off a high dose suddenly can make heroin cold turkey seem like a mild case of the sniffles. A bad case of benzodiazepine withdrawal produces months, if not years, of night-time panics and general anxiety. And the worst thing is: when it's going on, you won't have a clue whether you're experiencing "rebound anxiety" (a reaction to coming off the pills) or you've reverted to the anxious state that made you sweaty and sleepless in the first place.

So, all things considered, don't panic at the report in the BMJ Open - it doesn't say that sleeping pills will give you cancer or heart disease. But if the whole thing makes you uneasy enough to want to come off this insidiously addictive medication, then for God's sake make sure you consult a doctor first.

Damian Thompson's book 'The Fix: How Addiction is Invading our Lives and Taking Over Your World' is published by Collins in May.