A bad trip is an acute adverse psychological reaction to classic hallucinogens. It occurs when the trip a psychedelic drug causes is negative. During a bad trip, users may experience extreme psychological distress, such as anxiety, paranoia, and the unshakeable sense of ones inevitable and imminent personal demise or states of unrelieved terror that they believe will persist after the substances effects have worn off. Bad trips can lead to excessive fear, agitation, or emotionally disturbing situations. They can be exacerbated by the inexperience or irresponsibility of the user or the lack of proper preparation and environment for the trip, and are often reflective of unresolved psychological tensions triggered during the course of the experience.

There are several things that can increase the probability of a bad trip, but anyone who is using psychedelic substances is at risk of having a bad trip. Some of the things that can increase the risk of having a bad trip include being in a low mood, using the drug in a high-stimulation space, and mixing drugs with other substances, including alcohol.

Stopping a bad trip may not be possible, but there are things that can be done to help someone who is having a bad trip. If someone is having a bad trip, they should be moved away from noise and stimulation, as this can make a bad trip worse. A bad trip guide can also help. This involves having someone who is sober stay with the person having the bad trip and talk them through the trip. Some medications may help to stop a bad trip, but these can only be given in a hospital.

It is worth noting that bad trip experiences are common among users of psychedelics, and such experiences are often transformed into valuable experiences through storytelling. Bad trip narratives may be a potent coping mechanism for users of psychedelics in non-controlled environments, enabling them to make sense of frightening experiences and integrate these into their life stories.