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Research findings
2008 research finding

Sleeping pills can increase risk of traffic accidents

In 2008, researchers at the Norwegian Institute of Public Health (NIPH) found an increased risk of being involved in a road traffic accident after a patient has been prescribed this type of hypnotic (Imovane®, Stilnoct®). The risk can be compared with other hypnotics such as Apodorm® and Mogadon®.

Earlier research has shown an increased risk for traffic accidents when benzodiazepines have been prescribed. This group contains hypnotics, anxiolytics and sedatives. In recent years there has nevertheless been a great increase in the use of drugs in the z-hypnotic category (containing the active ingredient zopiclone (Imovane®), zolpidem (Stilnoct®) og zaleplon (Sonata®)). These substances have a shorter effect and are eliminated from the body faster than benzodiazepines. It is generally believed that these drugs have a lesser negative effect on driving “the morning after” than benzodiazepines.

In 2006, zopiclone-containing z- hypnotics were prescribed to 6 percent of the population between 18-69 years in Norway. Despite increasing use of these sleeping tablets throughout the world, there has been little study about any increased risk for road traffic accidents.

Researchers from the NIPH have published findings about the risks of being involved in a road traffic accident after being prescribed different hypnotics. The study was carried out based on data from three different registers and covered various hypnotics; zopiclone (Imovane®), zolpidem (Stilnoct®), nitrazepam (Apodorm®, Mogadon®) and flunitrazepam(Flunipam®, Rohypnol®). All inhabitants in Norway were included in the study via the Central Population Registry. Information on prescriptions and involvement in traffic accidents with injury was collected from the Norwegian Prescription Database and the Road Accident Registry respectively. The occurrence of accidents in the period after a hypnotic drug was dispensed (exposed period) was compared with the occurrence of accidents in the non-exposed period.

Increased risk

The study showed a clearly increased risk for traffic accidents the first week after prescriptions of the fore-mentioned hypnotics were dispensed. The risks after dispensing zopiclone, zolpidem and nitrazepam were comparable and increased over twice as much compared with non-exposed periods. For flunitrazepam the incidence risk was raised by 4-fold. These new results are alarming because zopiclone and zolpidem are considered to not affect driving ability when taken correctly in therapeutic doses before bedtime. The study therefore indicates that driving should be reduced in periods where people are exposed to these drugs.


Gustavsen I, Bramness JG, Skurtveit S, Engeland A, Neutel I, Morland J. Road traffic accident risk related to prescriptions of the hypnotics zopiclone, zolpidem, flunitrazepam and nitrazepam. Sleep Med. 2008