Pharmacoepidemiology of benzodiazepine and sedative-hypnotic use in a Canadian general population cohort during 12 years of follow-up.

Objective: benzodiazepines (BDZs) and similar sedative-hypnotics (SSHs) can have both beneficial and adverse effects. Clinical practice guidelines indicate that the course of treatment should usually be brief (a few weeks), but patients often take these medications for longer periods of time. We hypothesized that treatment with antidepressants (ADs) would be associated with a shorter duration of SSHs use as mood and anxiety disorders may underlie the symptoms usually targeted by BDZ treatment.

Methods: our study used data from a Canadian longitudinal general health study, the National Population Health Survey, which has collected data since 1994. Data are currently available to 2006. At each interview, all medications taken in the preceding 2 days are recorded. In our study, we used proportional hazard models to describe patterns of initiation and discontinuation of these medications in the general population.

Results: at each interview, the frequency of BDZ-SSH use was 2% to 3%. About 1% of the population initiated use in each 2-year follow-up period. Contrary to expectation, taking ADs predicted initiation of BDZ-SSHs, but not discontinuation.

Conclusions: unexpectedly, respondents taking ADs had a higher frequency of new BDZ-SSH use. AD use may be a marker for depression severity or comorbidity, such that the observed results may be an artifact of confounding by these factors. Irrespective of etiology, initiation of AD treatment does not appear to negate the risk of long-term BDZ-SSH use.