This page provides general harm reduction education only. It is not medical advice and cannot substitute for a consultation with a qualified healthcare provider who knows your full history. If you have a diagnosed psychiatric or medical condition, speak with your doctor before using any psychedelic substance. If you are currently in a mental health crisis, contact a crisis line or emergency services — this page is not the right starting point.
Medical Contraindications
Certain medical and psychiatric conditions significantly elevate the risk of harm from psychedelic use. The following are the most important and widely documented. This list is not exhaustive — if you have any chronic medical or psychiatric condition, the appropriate question is always: has my healthcare provider considered this?
Personal or family history of psychosis or schizophrenia-spectrum disorders
This is the firmest and most widely cited contraindication. Psychedelics activate the same neural systems implicated in psychotic disorders and can precipitate or exacerbate psychotic episodes in vulnerable individuals — including people who have never had a prior episode but carry a genetic predisposition. The risk is not limited to people who have personally experienced psychosis: a significant family history of schizophrenia or schizoaffective disorder is a serious caution even in the absence of personal psychiatric history.
The mechanism is not fully understood, but 5-HT2A receptor activity — the primary target of classical psychedelics — is directly implicated in the phenomenology of psychosis. For people with personal or family histories in this domain, there is no dose of psilocybin, LSD, or DMT that is clearly safe, and no preparation protocol that eliminates the risk.
Bipolar I disorder
Multiple case reports document psychedelic use precipitating manic episodes in people with bipolar I. The disorganising effects of high-dose psychedelics on mood regulation appear particularly risky in this population. Bipolar II may carry lower but not zero risk. If you have a bipolar diagnosis, discuss with your psychiatrist before any engagement — and be honest with them about what you are considering.
Active suicidal ideation
Psychedelics can amplify emotional distress as readily as they can produce insight and relief. Active suicidality — even passive ideation — is not an appropriate context for unmonitored psychedelic use. Research on psilocybin's anti-suicidal effects is promising, but those studies occur in carefully monitored clinical settings with intensive preparation and support. If you are struggling with suicidal thoughts, psychedelics outside of a clinical context are contraindicated. Please reach out to a crisis resource first.
Active severe trauma symptoms (untreated PTSD)
Psychedelics can surface traumatic material with great force and without predictable timing or intensity. For people with untreated or severely destabilised PTSD, this can be retraumatising rather than healing — particularly without experienced clinical support. People with trauma histories who are psychologically stable and have adequate therapeutic support may be reasonable candidates, but the calculus is meaningfully different from those without such histories. Trauma-informed clinical guidance is strongly advisable.
Cardiovascular conditions
Classical serotonergic psychedelics produce moderate but meaningful increases in heart rate and blood pressure. People with significant cardiac disease, uncontrolled hypertension, arrhythmias, or recent cardiac events should not use psychedelics without explicit clearance from a cardiologist. MDMA in particular produces pronounced cardiovascular stimulation and is firmly contraindicated in people with cardiovascular disease.
Liver conditions
Psilocybin and most classical psychedelics are hepatically metabolised. Significant liver impairment can affect metabolism and duration unpredictably. A less commonly considered but real factor.
Pregnancy and breastfeeding
No adequate safety data exists for psychedelic use during pregnancy or while breastfeeding. The appropriate position is: avoid entirely. This applies to all classical psychedelics, MDMA, ketamine, and ayahuasca — for which there are also MAOI interactions to consider.
Epilepsy
Some evidence suggests psychedelics may lower seizure threshold in susceptible individuals, and the combination of lithium (sometimes prescribed for epilepsy) with psychedelics has been associated with seizures. People with epilepsy should discuss with their neurologist.
Drug Interactions: A Detailed Overview
This is among the most practically important sections on this page. Many people are taking medications — prescribed or otherwise — whose interaction with psychedelics ranges from "reduces effects" to "potentially life-threatening." Know what you are combining before you combine anything.
| Substance / Class | Interaction with Classical Psychedelics | Risk Level |
|---|---|---|
| SSRIs (e.g., sertraline, fluoxetine, escitalopram) | Blunts or blocks psychedelic effects via serotonin reuptake inhibition and 5-HT2A receptor downregulation. Abrupt discontinuation to use psychedelics carries serious discontinuation syndrome risk. Do not stop SSRIs without medical guidance. | High — medical consultation required |
| SNRIs (e.g., venlafaxine, duloxetine) | Similar to SSRIs; also blunts effects and carries discontinuation risks. | High — medical consultation required |
| MAOIs — pharmaceutical (e.g., phenelzine, tranylcypromine) | Dramatically potentiates DMT (this is the basis of ayahuasca's pharmacology). With other psychedelics, risk of serotonin syndrome. Even dietary interactions with tyramine become relevant. | Dangerous — do not combine without expertise |
| Lithium | Multiple case reports of seizures and cardiac events when combined with classical psychedelics. The mechanism is not fully established. This combination should be avoided entirely. | Do not combine |
| Tramadol | Serotonergic opioid — serious serotonin syndrome risk, particularly with ayahuasca/MAOIs. Less severe risk with other psychedelics, but meaningful. | High |
| Antipsychotics (e.g., quetiapine, olanzapine, haloperidol) | Most antipsychotics block 5-HT2A receptors — they will blunt or fully block classical psychedelic effects. More importantly: if you are prescribed antipsychotics, your diagnosis is the primary contraindication concern, not the medication interaction. | High (diagnostic contraindication) |
| Cannabis / THC | Significantly intensifies and prolongs psychedelic effects — often unpredictably. High doses of THC during a psychedelic experience frequently produce anxiety, paranoia, and loss of grounding. One of the most common contributors to difficult experiences. Use with extreme caution if at all. | Moderate–High |
| Stimulants (amphetamines, cocaine) | Combined cardiovascular load; unpredictable psychological interaction. Increased anxiety risk. | Moderate |
| Benzodiazepines (e.g., diazepam, lorazepam) | Reduce or abort psychedelic effects by dampening neural excitability. Useful as an emergency intervention for overwhelming experiences — but taking benzos recreationally before or during a psychedelic experience undermines the experience itself. | Low (reduces effects; useful in crisis) |
| Alcohol | Dehydration, nausea amplification, and general impairment of the reflective quality of the experience. Avoid on the day of and ideally the day before. | Low–Moderate |
| St. John's Wort | A mild MAOI and serotonin reuptake inhibitor — can blunt effects and contributes to serotonin load. | Moderate |
For a comprehensive, interactive reference, the combination chart below is based on TripSit's data. Use it as a quick guide — always research independently before considering any combination.
Drug Combination Safety Chart
Select two substances to see their interaction rating and clinical notes.
A common and dangerous mistake: stopping SSRIs or other psychiatric medications abruptly in order to use a psychedelic. Antidepressant discontinuation syndrome can be severe, and destabilising your mental health in the weeks before a psychedelic experience is the opposite of good preparation. If you want to explore psychedelics while on psychiatric medication, this is a conversation to have with your prescriber — ideally with a psychiatrist who is knowledgeable about psychedelic interactions.
Psychological Readiness
Psychological readiness is not about being free of difficulty or in a perfectly stable state. It is about having sufficient stability and support to work constructively with what arises. These are meaningfully different standards.
What readiness looks like
You have a reasonably stable baseline — you are not in the midst of acute crisis, major life disruption, or ongoing trauma activation. You have access to support — a trusted person who knows what you are doing and can be reached if needed. You have time and space — the days around the experience, including the day after, are protected from high-stakes obligations. You have thought honestly about your intentions — not just what you hope for, but what you are afraid of, and why this feels like the right time.
Relative contraindications
These are not firm contraindications but meaningfully elevate the need for support and caution: significant unprocessed grief or loss in the recent past; active relationship crisis or major relational disruption; acute work or financial emergency; history of severe dissociation or derealization; first-time use with no guide, sitter, or support person.
Trauma history
Having a trauma history does not disqualify someone from working with psychedelics — some of the most significant therapeutic work involves exactly this population. But trauma history is a meaningful contextual factor that shapes how much support is needed, what substances and doses are appropriate, and how important it is to have a skilled facilitator. Someone with a significant trauma history attempting high-dose psilocybin alone for the first time is in a meaningfully different risk category than someone with no psychiatric history in the same scenario. Adjust accordingly.
Timing and Life Context
The timing of a psychedelic experience matters more than most preparation guides acknowledge. Psychedelics tend to surface whatever is most alive and unresolved in a person's life — which means that the texture of your life in the weeks before the experience will substantially shape what arises.
Favourable timing: A period of relative stability; adequate sleep in the weeks prior; no major unresolved interpersonal conflicts immediately before the experience; the day itself is calm, with no high-stakes obligations immediately preceding or following.
Unfavourable timing: In the immediate aftermath of a significant loss or relational rupture (unless you are specifically working with this material with appropriate support); during periods of acute work or life crisis; if you have been sleeping poorly for an extended period; if you are currently in a destabilised phase of psychiatric medication.
Some people use psychedelics during periods of grief or transition with meaningful benefit — but this is not a contradiction of the above. The key is the combination of timing, support, intention, and substance/dose. A low-to-moderate-dose psilocybin experience with a skilled sitter during a period of grief can be appropriate; the same dose alone in an unfamiliar space during an acute crisis is not.
Support Structures
Who knows you are doing this? Who can you reach if you need grounding support during the experience? Who will check in with you in the 24–72 hours that follow?
These questions are not formalities. The relational container within which a psychedelic experience occurs is part of its setting — and for many people, knowing that trusted support exists and is available is itself a significant stabilising factor.
Minimum for a moderate-to-high-dose experience: one person who is aware you are doing this, available to be reached, and knows what to do if you need support. Better: a sitter who is physically present. Better still: a trained facilitator or therapist, particularly for people with significant psychiatric history or intentions related to trauma or mental health.
Testing Your Substance
Harm reduction begins before the experience itself. Testing what you are about to take is one of the most concrete harm reduction actions you can take.
Ehrlich reagent: Turns purple in the presence of indole alkaloids — including psilocin (active mushroom alkaloid), LSD, and DMT. A positive result (purple/violet) indicates an indole alkaloid is present. A negative result (no colour change) for something sold as psilocybin mushrooms or LSD is a serious red flag.
Hofmann reagent: More specific for LSD — turns blue/green. Useful alongside Ehrlich for LSD verification.
Marquis reagent: For MDMA (purple/black), 2C-B (yellow-green), and distinguishing between substance classes.
Fentanyl test strips: Use for any pressed pill, powder, or substance of uncertain origin. Fentanyl contamination has been detected in MDMA, cocaine, and other substances. Test strips are inexpensive, increasingly available, and may save your life.
Test kits are available from DanceSafe (US and Canada shipping). In Canada, several harm reduction organisations offer drug checking services with more precise analytical methods — find your nearest service at drugchecking.ca.
Assessing by Substance
Different substances carry meaningfully different risk profiles, and "am I ready for psychedelics?" is in part substance-specific. Some relevant distinctions:
Psilocybin mushrooms: The most forgiving classical psychedelic for first experiences in terms of duration (4–6 hours) and physiological risk profile. Still requires honest psychological assessment. Dose matters enormously — a 1 g experience and a 5 g experience are not the same risk category.
LSD: Longer duration (8–12 hours) demands greater psychological stamina and more careful scheduling. The longer arc means that a difficult experience has a longer window in which to escalate and less predictable timing of resolution.
Ayahuasca: The MAOI interaction profile makes drug interaction assessment essential before anything else. Duration (4–6 hours, with multiple waves), purging, and the typically more confrontational emotional character require more preparation than many first-time users expect. Experienced facilitation is strongly advisable.
MDMA: Cardiovascular assessment is especially relevant. The entactogenic character is different from classical psychedelics — but the vulnerability it creates and the emotional material it surfaces still require integrative support.
Ketamine: Dependence potential distinguishes it from classical psychedelics. If you have a history of substance use disorders, this is a meaningful risk factor for ketamine specifically.
Crisis Resources
Fireside Project — The most important resource for psychedelic crisis support in North America. Free, confidential, peer-supported. Call or text 62-FIRESIDE (623-473-7433). They are trained specifically for psychedelic distress and will not contact emergency services unless there is a genuine medical emergency.
TripSit — Online chat support and the most widely used drug interaction database. tripsit.me
Crisis Services Canada — 1-833-456-4566. 24/7 crisis support.
Talk Suicide Canada — 1-833-456-4566 (call) or text 45645 (text, 4pm–midnight ET).
Frequently Asked Questions
SSRIs significantly blunt or block the effects of psilocybin through 5-HT2A receptor downregulation. Many people on SSRIs report little or no effect from typical doses of psilocybin. Some choose to discontinue their SSRI before a session — but this must be done carefully and with medical guidance. Abrupt discontinuation of many SSRIs causes discontinuation syndrome. Fluoxetine (Prozac) has a very long half-life and takes weeks to clear. This is a conversation for your prescriber, ideally one with psychedelic medicine knowledge.
Anxiety history is a contextual factor, not an absolute contraindication. Psychedelics can amplify anxiety — but they can also be profoundly anxiety-resolving when context is right. Key variables: severity and current stability of the anxiety; whether there is a concurrent diagnosis that is a firmer contraindication (panic disorder with severe agoraphobia, for example); substance and dose chosen (lower doses and psilocybin over LSD tend to be more manageable for anxious individuals); and the quality of support. Someone with mild generalised anxiety who is psychologically stable and has good support is in a very different situation from someone in active panic disorder.
Family history of schizophrenia is a meaningful contraindication — not a certainty of harm, but a significant elevation of risk that most harm reduction frameworks treat as a firm caution. The precise risk is not well quantified in the literature, partly because people with this history are typically excluded from clinical trials. The honest answer is: the risk is real and not well understood, and the appropriate response to genuine uncertainty about something this significant is caution rather than experiment. This is one of the situations where conversation with a psychiatrist who knows psychedelic medicine is strongly advisable before proceeding.