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The War on Drugs: History, Policy, and Therapeutics

Potentially Negative Side Effects of Psychedelics

Potential Classic Hallucinogen Negative Short-Term Effects

Along with hallucinations, other short-term general effects include:

  • increased heart rate
  • nausea
  • increased blood pressure, breathing rate, or body temperature
  • loss of appetite
  • dry mouth
  • sleep problems
  • uncoordinated movements
  • excessive sweating
  • panic
  • paranoia—extreme and unreasonable distrust of others
  • psychosis—disordered thinking detached from reality
  • bizarre behaviors

Potential Long-Term Effects

Hallucinogens can cause severe visual disturbances.

Two long-term effects have been associated with use of classic hallucinogens, although these effects are rare.

  • Persistent Psychosis—a series of continuing mental problems, including:
    • visual disturbances
    • disorganized thinking
    • paranoia
    • mood changes
  • Hallucinogen Persisting Perception Disorder (HPPD)—recurrences of certain drug experiences, such as hallucinations or other visual disturbances. These flashbacks often happen without warning and may occur within a few days or more than a year after drug use. These symptoms are sometimes mistaken for other disorders, such as stroke or a brain tumor.

National Institute on Drug Abuse. (2021, June 30). Hallucinogens DrugFacts. National Institute on Drug Abuse. Retrieved from

What Is a “Bad Trip”?

When someone has a prolonged negative experience while using hallucinogens, it is commonly referred to as a “bad trip.”

Bad trips can be extremely unpleasant and frightening experiences, and their occurrence is often quite unpredictable—it is not possible to guarantee a good trip on any hallucinogen. However, avoiding very high doses and remaining in a safe and secure environment can help to mitigate the risk. 

If you’re with someone having a bad trip, you might try to help by getting them away from others and from too much stimulation such as loud noises. Continually reassure them that they are safe and that the high will wear off in time.

Regan, J. (2020, November 5). Hallucinogens: What are they and what are their effects? Oxford Treatment Center. Retrieved from

Hartney, E. (2020, May 18). How to cope with a bad acid trip. Verywell Mind. Retrieved from

Potentially Positive Effects of Psychedelics

Potential Classic Hallucinogen Positive Side-Effects

Potential Classic Hallucinogens Short-Term Effects

From "Sustained, Multifaceted Improvements in Mental Well-Being Following Psychedelic Experiences in a Prospective Opportunity Sample" 

Mans, K., Kettner, H., Erritzoe, D., Haijen, E. C., Kaelen, M., & Carhart-Harris, R. L. (2021). Sustained, multifaceted improvements in mental well-being following psychedelic experiences in a prospective opportunity sample. Frontiers in Psychiatry, 12.

"Results supported our main prior hypothesis that psychedelic experiences lead to broad increases in well-being in those that have a prior intention to use a psychedelic compound, and well-being scores remained elevated 2 years after the experience.

Scores on both identified factors Being Well and Staying Well were significantly increased post-psychedelic use. These factors can be seen as reflecting:

(1) a current state of being well, e.g., higher trait optimism, positive affect, and self-esteem; and

(2) a more prospective staying well factor, which covers attributes such as resilience, psychological flexibility, and mindfulness—three constructs that are found to be inter-related and contribute to positive mental health...

In line with this, the current study found these phenomena changing together after a psychedelic experience.

These findings lend support to the view that psychedelics have a general positive effect on well-being; promoting psychological wellness and resilience in the medium to long-term. Considering the current magnitude of the burden of mental illness, its increasing prevalence, and the growing costs of healthcare associated with mental illness, promotion and longer-term protection of well-being (“staying well”) is considered a priority area and could yield personal, social, and economical benefits..."