People who use sleeping pills and/or anti-anxiety drugs may have an increased risk of death, a new study suggests.

UK scientists followed the progress of almost 35,000 people for seven-and-a-half years. All of the participants were prescribed either an anxiolytic (anti-anxiety) drug or a hypnotic (sleeping) drug at the start of the study.

Benzodiazepines were the most commonly prescribed class of drug. Also known as sedatives or tranquillisers, these are a group of medications that help to regulate sleep, ease agitation and reduce anxiety. They include diazepam (Valium).

Most of the participants received more than one type of drug over the course of the study.

The scientists found that many of these drugs doubled the risk of mortality.

"The key message here is that we really do have to use these drugs more carefully. This builds on a growing body of evidence suggesting that their side-effects are significant and dangerous. We have to do everything possible to minimise over reliance on anxiolytics and sleeping pills," commented Prof Scott Welch of the University of Warwick.

However, he emphasised that the findings do not suggest that these drugs are not effective.

"But particularly due to their addictive potential, we need to make sure that we help patients to spend as little time on them as possible and that we consider other options, such as cognitive behavioural therapy, to help them to overcome anxiety or sleep problems," he said.

Details of these findings are published in the British Medical Journal.