Analysing psychiatric side‐effects of beta‐blockers using large computerized data bases

Abstract Objective — To use a large computerized data base to evaluate the relationship between beta‐blockers and psychiatric side‐effects. Design — The hybrid design included retrospective cohort and case‐control studies. Setting — A Swedish municipality of around 20,000 inhabitants during 1980–1982. Participants — All new users of beta‐blockers ( N = 542) were identified. Unexposed individuals without previous use of cardiovascular drugs were assigned from the data base through category matching by age and sex. Main outcome measure — Prescriptions of sedatives, hypnotics, and antidepressants filled in the 365 days preceding or following the index date. Results — The case‐control analysis showed that previous use of sedatives, hypnotics or antidepressants was common among new users of beta‐blockers, demonstrating a history of psychiatric problems. The cohort analysis showed that new users started using sedatives, hypnotics, or antidepressant drugs to a greater extent than those who were not exposed to beta‐blockers, after controlling for three confounding variables: previous use of sedatives, hypnotics, or antidepressants; heavy use of physician visits; and heavy use of prescription drugs. There were no statistically significant differences in psychotropic use between users of propranolol and users of other beta‐blockers. Conclusions — In spite of the positive finding, we did not establish a causal relationship between beta‐blockers and psychiatric side‐effects. Our data base lacked information to control for confounders like personality, stress, life events, or working environment. Neither could we control for confounding by indication, which must be important, considering the strong relationship between prior use of psychotropics and new use of beta‐blockers. The methodological problems in this study illustrate some of the difficulties of using large computerized data bases for analysing adverse drug effects.