text: A bad trip (also known as challenging experiences, acute intoxication from hallucinogens, psychedelic crisis, or emergence phenomenon) is a term describing an acute adverse psychological reaction to effects produced under the influence of psychoactive substances, namely psychedelics. There is no clear definition of what constitutes a bad trip. Additionally, knowledge on the cause of bad trips and who may be vulnerable to such experiences are limited. Existing studies report that possible adverse reactions include, anxiety, panic, depersonalization, ego dissolution, paranoia, as well as physiological symptoms such as dizziness and heart palpitations. However, most studies indicate that the set and setting of substance use influence how people respond.
  With proper screening, preparation, and support in a regulated setting these are usually benign. A bad trip on psilocybin, for instance, often features intense anxiety, confusion, agitation, and psychosis. They manifest as a range of feelings, such as anxiety, paranoia, the unshakeable sense of one's inevitable and imminent personal demise or states of unrelieved terror that they believe will persist after the substance's effects have worn off. As of 2011, exact data on the frequency of bad trips are not available.