Medical Contraindications to “Classic” Psychedelic Use

Gowri Aragam
March 22, 2022
Abstract Acrylic Painting
Photo by Pawel Czerwinski on Unsplash

What is a classic psychedelic?

“Classic Psychedelics” include Psilocybin (Magic Mushrooms), LSD (Acid), DMT (Ayahuasca), and Mescaline (Peyote). These substances are grouped together as “classic” because they all impact the same Serotonin receptors in the brain, specifically 5HT-2A [1]. In the past couple decades, there has been growing evidence for the use of classic psychedelics to treat psychiatric disorders including depression, anxiety, PTSD, OCD, Substance Use Disorders, especially when standard treatments have not been successful [1]. These psychedelics are typically used in the setting of psychedelic assisted therapy, where a person is monitored by a clinician and guided through therapeutic questions over the course of many hours in a controlled setting.

The doses of classic psychedelics used to treat these conditions have been found to be relatively safe overall [2]. However, this does not mean that they are safe for everyone. Very importantly, the side effects that do occur can be very dangerous for people with certain medical and psychiatric issues, to the extent that psychedelic use is contraindicated in these groups of people.

What is a contraindication?

A contraindication is a reason a person should not receive a particular treatment due to the risk of significant medical or psychological harm. A relative contraindication is a medication/diagnosis/symptoms that makes a treatment higher risk for a person, but could be advisable if benefits of the treatment outweigh the risks [3]. An absolute contraindication is something that cannot be used under any circumstance due to the high level of risk. Medical harm constitutes harm to a person’s physical body, such as stroke, heart attack, death, while psychological harm constitutes harm to a person’s mental health, such as psychosis, emotional dysregulation, suicidality.

What are the medical contraindications to classic psychedelic treatment?

Let’s discuss contraindications as they pertain to side effects to psychedelics. The most common medical side effect of classic psychedelics is an elevation in blood pressure and heart rate. While this effect can be safe for most people to tolerate, it is dangerous for others whose bodies cannot safely handle high blood pressure. As a result, psychedelics are contraindicated if someone is pregnant, or has a history of epilepsy/other seizure disorder, or severe cardiovascular disease including uncontrolled blood pressure, heart failure, coronary artery disease or previous heart attack or stroke [3].

Because psychedelics work by activating Serotonin receptors in the brain, they can lead to a life threatening condition called Serotonin Syndrome if used in conjunction with other medications or substances that also increase Serotonin levels in the brain. As a result, they are contraindicated in people using medications like SSRI or MAO-I antidepressants who are not able to be weaned off of these medications before treatment [3].

What are the psychiatric contraindications to classic psychedelic treatment?

Another potential effect of psychedelics is prolonged psychosis. While this side effect is very rare in the general population, it can be incredibly dangerous for people who have a personal or family history of primary psychotic or affective disorders like Schizophrenia, Schizoaffective disorder, or Bipolar 1 disorder.  It can also be dangerous for people who experience psychotic symptoms in the setting of depression. This is because it can increase the risk of psychotic episodes in these groups of people [3].

People with significant trauma histories who have not yet learned fundamental coping skills or developed a safety plan (e.g. the stabilization phase of trauma treatment) should not take psychedelics for the same reason they should not engage in therapies like cognitive processing therapy or prolonged exposure. Psychedelics can lead to reliving traumatic experiences, and opening up repressed traumatic memories that can lead to significant emotional upheaval that can have [4].

Similarly, psychedelics are contraindicated in people who’ve previously experienced any adverse effect from these substance such as prolonged psychosis or suicidal ideation [3].


If someone is considering engaging in psychedelic assisted treatment for a psychiatric or psychological issue, it is imperative to discuss this with a trained medical professional before use. There is still significant research being done into the potential medical and psychiatric complications of psychedelic use, so it is important to discuss the nuances of your particular medical history with a professional before moving forward with treatment.


  1. Johnson MW, Hendricks PS, Barrett FS, Griffiths RR. Classic psychedelics: An integrative review of epidemiology, therapeutics, mystical experience, and brain network function. Pharmacol Ther. 2019 May;197:83-102. doi: 10.1016/j.pharmthera.2018.11.010. Epub 2018 Dec 4. PMID: 30521880.
  2. Jacob S. Aday, Cayla M. Mitzkovitz, Emily K. Bloesch, Christopher C. Davoli, Alan K. Davis, Long-term effects of psychedelic drugs: A systematic review, Neuroscience & Biobehavioral Reviews, Volume 113, 2020, Pages 179-189, ISSN 0149-7634,
  3. Frecska, Ede. (2007). Therapeutic guidelines: dangers and contra-indications in therapeutic applications of hallucinogens. 10.13140/RG.2.1.2364.8888.
  4. Erwin Krediet, Tijmen Bostoen, Joost Breeksema, Annette van Schagen, Torsten Passie, Eric Vermetten, Reviewing the Potential of Psychedelics for the Treatment of PTSD, International Journal of Neuropsychopharmacology, Volume 23, Issue 6, June 2020, Pages 385–400,

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