A mystical experience questionnaire is a survey about someone's experience with psychedelic drugs, usually completed by the individual immediately after the experience is over. The original version had 43 items, but the revised version was shortened to 30 items. The questionnaire is frequently used in research studies where psychedelic drugs are involved. The questionnaire has been in use since the 1960s, and the shortened version is still used to this day. Numerous questions focus on someone's overall emotional state, seeking to figure out how it changed before, during, and after the experience. Some people take the questionnaire regularly to chart changes in how they feel over time.