In safety assessments of new drugs for neuropsychiatric disorders, based on the clinical significance, the focus has been on factors such as the suicide risk and abuse potential. In recent years, it has been considered as important to evaluate drug effects on the ability to operate a motor vehicle. In the development of medicinal products for the treatment of insomnia, the recommended doses are determined on the basis of the results of clinical trials including driving studies. Evaluating the results of clinical trials (clinical pharmacology, exploratory, confirmatory, and long―term studies) is useful to clarify the safety profile of a new drug; however, it is necessary in order to conclude the magnitude of drug effects on the driving ability to perform driving studies, with the purpose of clarifying a dose that does not affect the driving ability. There has also been an accumulation of evidence to examine the impact of psychotropic drugs on driving ability. In this paper, methodological issues on evaluation of drug effects on the ability to operate a motor vehicle are discussed.
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