Effects of long-term benzodiazepine medication. A prospective cohort study: methodological and clinical aspects.

Benzodiazepine (BDZ) drug impact on mental functions was explored in a cohort study of 30 psychiatric outpatients on long-term BDZ medication. A new questionnaire, the Drug Impact on Mental Processes (DIMP) was used and evaluated. The patients were rated three times: on inclusion in the study, after about 18 months and, finally, only a few days later. Test-retest reliability was evaluated for the two last ratings and was found acceptable for 19/23 items. The DIMP scores indicated negative effects on crisis reaction, intensified defence mechanisms and reduced cognitive, emotional and conative functions. Long-term BDZ treatment intensified passive coping. The drug impact on mental functions ranged between a mild and a moderate degree. The clinical outcomes of the patients' psychiatric disorders were evaluated at a 1-year follow-up after continued or discontinued BDZ treatment. In the subgroup that had discontinued the BDZ treatment at follow-up, significantly more patients reported reduced severity of their psychiatric disorders and significantly more patients had paid jobs. The overall clinical improvement after discontinued BDZ treatment may be explained by recovery from an addiction syndrome. It may also be related to a shift from passive to active coping.