Who should not take psychedelics? (contraindications)

A personal or family history of psychosis, schizophrenia, or bipolar disorder is the clearest contraindication — clinical screening guidelines exclude it outright. Beyond that, uncontrolled cardiovascular conditions, pregnancy and breastfeeding, certain medications (MAOIs and lithium above all), and active substance use disorder round out the core exclusion list researchers use before anyone is given a psychedelic in a study. None of this is a self-diagnosis checklist — it's context to bring to a real screening conversation.

Clinical trials don't give psychedelics to anyone who walks in the door — they screen people out first, and the exclusion criteria researchers settled on are the most reliable public answer to "who shouldn't do this." The foundational safety guidelines for hallucinogen research, published by a Johns Hopkins team in 2008 and still the reference point for the field, lay out exactly which histories and conditions rule someone out (Johnson, Richards & Griffiths, 2008). This page walks through that list.

1. Personal or family history of psychosis, schizophrenia, or bipolar disorder

This is the exclusion researchers treat as closest to absolute. The 2008 Hopkins guidelines exclude anyone with a personal history of schizophrenia or another psychotic disorder, bipolar I or II disorder, or a first- or second-degree relative with either — and note that family history alone carries "approximately a six-fold greater chance of developing schizophrenia in second-degree relatives." The concern is specific: classic psychedelics can trigger a psychotic or manic episode in someone already vulnerable to one, even without any prior episode of their own. This is a genetic-vulnerability risk, not something screened out by "how you're feeling" on a given day (Johnson et al., 2008; UCSF Translational Psychedelic Research Program).

Related but narrower exclusions in the same guidelines: current major depression with psychotic features, and — for some research teams — high scores on personality measures of rigidity and emotional lability, traits "significantly associated with negative experiences during hallucinogen action."

2. Uncontrolled cardiovascular conditions

Classic psychedelics produce a real, if usually modest, rise in heart rate and blood pressure. Research protocols exclude resting blood pressure above 140/90 mmHg averaged across separate assessments, and clinicians widely extend that caution to heart failure, coronary artery disease, and a history of heart attack or stroke (Johnson et al., 2008; UCSF). Epilepsy and other seizure disorders are grouped here too. None of this is a reason to self-diagnose — it's a reason a real screening conversation checks blood pressure and cardiac history rather than taking someone's word for it.

3. Pregnancy and breastfeeding

Pregnancy is a standard exclusion, largely because of the same blood-pressure effect combined with an almost complete absence of safety research in pregnant populations — there's nothing to weigh the theoretical risk against. The same caution is extended to breastfeeding (UCSF; Psychedelic Support).

4. Medication interactions

SSRIs, SNRIs, and tricyclic antidepressants are a different situation — usually not dangerous, but the 2008 Hopkins guidelines flag that acute SSRIs, tricyclics, and even St John's Wort can meaningfully change how a session unfolds. For the specific and very common question of SSRIs, see can I take psilocybin if I'm on SSRIs or antidepressants? — the short version is that it's a prescriber's question, not a guide's or a website's.

5. Active substance use disorder

Active, unmanaged substance use disorder is a standard screening exclusion — it complicates informed consent, judgment during a session, and follow-through on preparation and integration. This is separate from the growing body of research into psychedelic-assisted approaches to addiction itself, which happens in structured clinical settings, not as a workaround for an unrelated recreational session (Psychedelic Support).

Frequently asked questions

Sources

• Johnson MW, Richards WA, Griffiths RR. Human hallucinogen research: guidelines for safety. J Psychopharmacol. 2008;22(6):603–620.
• UCSF Translational Psychedelic Research Program: Medical contraindications to classic psychedelic use.
• Psychedelic Support: Who shouldn't take psychedelics.
• Nayak SM et al. Classic psychedelic coadministration with lithium, but not lamotrigine, is associated with seizures. Pharmacopsychiatry. 2021;54(5):240–245.