A "bad trip" is a highly unpleasant psychedelic experience. A bad trip on psilocybin, for instance, often features intense anxiety, confusion, and agitation, or even psychotic episodes. Bad trips can be connected to the anxious ego-dissolution (AED) dimension of the APZ questionnaire used in research on psychedelic experiences. As of 2011, exact data on the frequency of bad trips are not available. In clinical research settings, precautions including the screening and preparation of participants, the training of the session monitors who will be present during the experience, and the selection of appropriate physical setting can minimize the likelihood of psychological distress. In most cases in which anxiety arises during a supervised psychedelic experience, reassurance from the session monitor is adequate to resolve it; however, if distress becomes intense it can be treated pharmacologically, for example with the benzodiazepine diazepam.