Epidemiology of anxiolytic and hypnotic drug use in the general population in Norway

Background Drugs for mental disorders have been on the market for more than 50 years, but there is still a need for more knowledge about the use and impact of these drugs in real-life conditions. Appropriate use of anxiolytics or hypnotics may relieve or reduce severe problems, whereas inappropriate use may represent problems of personal or public health. Aims This thesis aims to study the epidemiology of anxiolytic and hypnotic drug use and, to a lesser extent, antidepressant drug use in the general population in Norway - in both cross-sectional and prospective cohort studies. Material and methods This thesis is based on data from 1) four health surveys done by the National Health Screening Service (now the Norwegian Institute of Public Health) in the counties of Østfold in 1985/1988 and Aust-Agder in 1986/1989, and in Oslo and Oppland/Hedmark in 2000-2001 and 2) the Norwegian Prescription Database (NorPD). Information on drug use was at first collected from health surveys, later from NorPD. Mental health status was measured by the screening tool “Hopkins symptom checklist” (HSCL-10) that was part of the health surveys. Information on deaths was obtained from the Norwegian Causes of Death Register. Results - Daily users of anxiolytics or hypnotics showed higher crude mortality than non-users. However, after adjustment the difference was markedly reduced. - The majority of incident users of hypnotics received prescriptions for z-hypnotics (benzodiazepine related drugs) rather than benzodiazepines, the choice of benzodiazepines predicted most strongly by previous use of anxiolytics and male gender. - The main factor associated with use of anxiolytics or hypnotics among people with mental distress was the use of analgesics. - The main factor associated with use of antidepressants among people with mental distress was not participating in the labour market. - Mental distress was a predictor of later use of anxiolytic drugs. - Women showed a higher proportion of use of psychotropic drugs than men, and there were also gender differences when studying mortality and incidence rates. Conclusion The health surveys offered selection bias and information bias that was eliminated when data were retrieved from NorPD. The health survey study populations were large enough to minimize random error, and from NorPD complete data were collected. The finding encourage general practitioners to be observant on mental distress as this is related to later anxiolytic drug use, that for selected populations is further associated with increased mortality. The gender differences observed for mortality, prevalence and incidence rates may lead us to question whether women suffer from more anxiety and depression than men, if they complain more, or if the truth is a combination of the two arguments