The single most important question in psychedelic decision-making is rarely framed correctly. It is not "should I try a psychedelic." It is "should I not try one right now." The first question carries momentum, hope, and the gravitational pull of a planned retreat. The second question is the screening question. Across 900-plus integration sessions, including post-session crisis triage where the screening that should have happened did not happen, the pattern is consistent. The people who run into serious trouble are almost always people who met at least one absolute contraindication and proceeded anyway.
This article consolidates the contraindications that fragmented sources cover in pieces. The MAPS Phase 3 MDMA-PTSD exclusion criteria, published in the Mitchell et al. 2021 Nature Medicine paper, are one anchor. The Nayak 2021 review on lithium and psychedelic seizure risk is another. The Studerus 2011 work on adverse event predictors gives the framework for relative contraindications. Together these sources draw a coherent map of when a psychedelic session should not happen, regardless of how aligned the rest of the picture looks.
The frame for the rest of this piece is simple. Absolute contraindications are hard stops. Relative contraindications are conditional stops requiring clinician evaluation and case-by-case judgment. Both categories matter. For deeper coverage of specific risk axes, see psychedelics and bipolar screening, the lithium warning, SSRIs and psychedelics, and cardiovascular safety.
- Roughly 47 percent of documented lithium plus classic psychedelic combinations were associated with seizures or seizure-like events, per the Nayak 2021 review across 47 case reports.
- Personal or first-degree family history of Bipolar I or II, schizophrenia, or other primary psychotic disorders are absolute contraindications across every major clinical trial protocol.
- Active SSRI use is a medication-specific issue. MDMA requires a structured taper because of serotonin syndrome risk. Classic psychedelics are usually blunted rather than dangerous, but conservative tapering remains the rule.
- Cardiovascular contraindications include uncontrolled hypertension, recent cardiac events, and known ventricular arrhythmias because 5-HT2B activation drives transient blood pressure and heart rate increases.
- Pregnancy and breastfeeding are absolute contraindications because no human safety data exists. Active suicidality requires psychiatric stabilization before any psychedelic decision is considered.
- Relative contraindications, including active substance use disorder, severe personality disorders, HPPD history, and a recent major life crisis, require clinician evaluation rather than a default proceed.
Why Do Contraindications Matter More Than Indications?
Most catastrophic outcomes in psychedelic sessions trace back to a contraindication that was either unknown to the participant, undisclosed to the operator, or disclosed and disregarded. Studerus and colleagues in 2011 analyzed adverse events across 110 psilocybin sessions and found that prior psychiatric history, set, and dose were the dominant predictors of difficult experiences (Studerus et al., 2011). The benefit side is well-publicized. The contraindication side is what determines whether the session is even a reasonable option.
The reframe matters because momentum is the enemy of careful screening. By the time a founder has paid for the retreat, booked the flights, and told their inner circle they are going, the psychological cost of not going feels enormous. The screening conversation needs to happen weeks or months earlier, before the commitment cascade has locked in. In my practice this is the first conversation, not the last.
The contraindications below are organized by certainty. Absolute means no, outside of monitored research. Relative means conditional, requiring clinician evaluation and a specific risk-benefit assessment for the individual. The boundary between the two is not always rigid. A relative contraindication can become absolute when stacked with others. Two relative contraindications combined often function as an absolute stop in conservative protocols.
According to the Mitchell 2021 MAPS Phase 3 protocol published in Nature Medicine, eligible participants were screened against an exclusion list that included primary psychotic disorder, Bipolar I disorder, dissociative identity disorder, current substance use disorder, uncontrolled hypertension, prior serious cardiovascular events, pregnancy, lactation, current SSRI use without taper, and active suicidality. The protocol also excluded participants whose recent life stressors or current medication regimens could not be safely stabilized across the dosing window. The shared logic across MAPS, COMPASS Pathways, and Usona trial exclusions is that contraindication screening is a single integrated filter rather than a list of independent checks, because risk concentrators stack multiplicatively. The clinical implication for non-trial contexts is that any operator who does not actively screen against this same list is taking on liability the trials themselves declined to take.
What Are the Absolute Contraindications for Psychedelics?
Absolute contraindications are conditions under which psychedelics should not be used outside of a monitored research protocol, regardless of dose, setting, or operator skill. The Mitchell 2021 MAPS protocol and the consensus exclusion lists from COMPASS Pathways, Usona, Johns Hopkins, and Yale converge on roughly the same eight categories. Each carries a documented safety signal that no current retreat or underground context is equipped to manage.
Bipolar I or II, Personal or Family
Personal history of Bipolar I or Bipolar II is the most consistently excluded condition in psychedelic research. The signal is treatment-emergent mania or hypomania, often arriving in the post-session plasticity window rather than during the dose itself. First-degree family history, meaning a parent or sibling with confirmed bipolar disorder, is treated as an absolute or near-absolute contraindication across most modern protocols because the genetic loading is meaningful even in the absence of personal expression.
Schizophrenia and Primary Psychotic Disorders
Personal or first-degree family history of schizophrenia, schizoaffective disorder, or other primary psychotic disorders is a categorical exclusion. Classic psychedelics are 5-HT2A agonists, and the same receptor system is implicated in psychotic symptom production. Triggering a first psychotic break in a vulnerable individual is a documented outcome with episode durations measured in months and frequent need for inpatient stabilization.
Pregnancy and Breastfeeding
Pregnancy and breastfeeding are absolute contraindications because zero human safety data exists. Animal data is sparse and not directly translatable. The plausibility of fetal or infant harm is high enough, and the absence of human evidence wide enough, that every major clinical trial excludes both states without exception. There is no benefit framing that justifies the unknown risk.
Active Suicidality and Psychiatric Crisis
Active suicidality, current psychotic symptoms, an unresolved trauma in the acute phase, or any acute psychiatric crisis are absolute contraindications. The reason is that the session will amplify what is already destabilized rather than resolve it. Psychiatric stabilization, often involving medication adjustment and crisis-stage therapy, needs to come first. Only after a period of confirmed stability, typically months, does psychedelic consideration become a question worth re-opening.
Which Medications Make Psychedelics Dangerous?
Lithium is the single most dangerous combination, with a roughly 47 percent rate of seizure or seizure-like events documented across 47 case reports of lithium plus classic psychedelics (Nayak et al., 2021). The mechanism is not fully characterized but is thought to involve lithium lowering the seizure threshold while serotonergic psychedelics drive cortical excitation. This is a hard stop, not a relative caution. Anyone currently on lithium should not take a classic psychedelic.
SSRIs and SNRIs
SSRIs blunt the subjective effects of classic psychedelics through 5-HT2A receptor downregulation. The interaction is substance-dependent. For psilocybin and LSD, the acute risk of serotonin syndrome with SSRIs is generally considered low, but the experience is often muted enough that participants chase higher doses, which introduces a different risk profile. For MDMA, the SSRI interaction is more serious. MAPS protocols mandate a structured taper because SSRIs both blunt MDMA effects and meaningfully elevate serotonin syndrome risk in combination.
The conservative position across operator types is that any SSRI taper happens with the prescribing clinician, across two to six weeks depending on the specific medication, and not unilaterally. The dangers of unsupervised SSRI discontinuation, including discontinuation syndrome and rebound depression, often exceed the dangers of the SSRI plus psychedelic interaction itself.
MAOIs, Tricyclics, and Stimulants
Monoamine oxidase inhibitors combined with serotonergic psychedelics produce a high risk of serotonin syndrome, with documented cases of severe hyperthermia, seizures, and death. This is a categorical hard stop. Tricyclic antidepressants and lithium-augmented protocols share the seizure-threshold risk and are likewise treated as contraindications. Stimulant medications, including dextroamphetamine and methylphenidate at therapeutic doses, are not absolute contraindications but they are mania concentrators in vulnerable individuals and should be reviewed with the prescribing clinician.
Cardiovascular Considerations
Uncontrolled hypertension, recent cardiac events within six months, known ventricular arrhythmias, and significant cardiac structural abnormalities are absolute contraindications across most protocols. Classic psychedelics produce transient blood pressure and heart rate increases through 5-HT2B and adrenergic activation. The acute hemodynamic load is usually well tolerated by healthy participants but becomes dangerous when superimposed on a compromised cardiovascular substrate. MDMA carries an even larger cardiovascular load and broader exclusion list.
Nayak and colleagues in 2021 reviewed 47 case reports of lithium combined with classic psychedelics, primarily psilocybin and LSD, drawn from PsychonautWiki, peer-reviewed case literature, and clinical reports. Approximately 47 percent of these combinations were associated with documented seizures or seizure-like events, including tonic-clonic activity, loss of consciousness, and hospital admission. The proposed mechanism involves lithium lowering the cortical seizure threshold while 5-HT2A agonism by the psychedelic drives glutamatergic excitation, producing a multiplicative excitatory load. The clinical implication is unambiguous. Lithium is an absolute contraindication for classic psychedelic use in any non-research context, regardless of dose, setting, or operator skill, because seizure monitoring and rapid medical intervention infrastructure is not available outside of hospital-grade environments. Discontinuation of lithium prior to a psychedelic session creates a separate destabilization risk in bipolar populations and is not a workaround.
What Are the Relative Contraindications?
Relative contraindications are conditions that do not categorically rule out a psychedelic session but require clinician evaluation, careful risk-benefit weighing, and often additional safeguards that retreat contexts cannot reliably provide. The boundary between relative and absolute is fluid. Two relative contraindications stacked together often function as an absolute stop in conservative protocols, because risk concentrators rarely act independently.
Active Substance Use Disorder
Active substance use disorder, particularly involving alcohol, benzodiazepines, opioids, or stimulants, is a relative contraindication that functions closer to absolute in practice. Benzodiazepines blunt psychedelic effects and have a specific dependency profile that needs to be addressed before a session. Heavy alcohol use creates liver-load concerns and behavioral disinhibition that compounds session risk. The general standard is meaningful sobriety, often 30 to 90 days, before a session is considered, and this is a screening point that retreat operators frequently underweight.
Severe Personality Disorders
Severe borderline personality disorder, narcissistic personality disorder, and antisocial personality disorder presentations are relative contraindications because the post-session integration window depends on a coherent sense of self that can hold and metabolize what surfaced. In severe presentations the integration arc is more likely to produce destabilization than synthesis. Mild to moderate trait expressions are not the same as full disorders, but the screening conversation needs to be honest about which is present.
HPPD History
Hallucinogen Persisting Perception Disorder, or HPPD, is a documented though uncommon outcome of psychedelic use, characterized by persistent visual disturbances such as palinopsia, trailing, and floaters. A prior episode of HPPD is a relative contraindication for further use because the recurrence rate after a second session in someone with prior HPPD is elevated. Some practitioners treat any confirmed HPPD history as an absolute stop. The conservative position depends on how disabling the prior episode was.
Major Life Crisis Within 30 to 90 Days
Acute bereavement, fresh divorce, recent job loss, or any major trauma still in the acute phase is a relative contraindication. The session amplifies whatever is alive in the nervous system. A life that is actively destabilizing does not provide the integration ground that the post-session plasticity window needs. The minimum stability window I recommend is 30 days. The more conservative threshold is 90 days, particularly for bereavement. The wait is not a delay. It is a precondition.
No Integration Support or Pre-Session Medical Screening
The absence of integration support is its own contraindication. A session without a follow-up structure has a substantially worse outcome profile than the same session with two to four integration sessions in the four weeks following. Likewise, the absence of a pre-session medical screening, including cardiovascular evaluation and medication review, is itself a reason to defer the session until proper screening is in place. Operator quality is the variable here, and choosing an operator who declines participants is a better signal than choosing one who accepts everyone.
Studerus and colleagues in 2011 analyzed pooled psilocybin data from eight Swiss experimental studies covering 110 healthy volunteers across 227 dosing sessions. The Studerus framework identified emotional excitability, low ego strength, current psychiatric symptom load, and unsupportive set or setting as the primary predictors of acute adverse responses including anxiety, paranoia, and ego dissolution distress. The Mitchell 2021 MAPS Phase 3 MDMA-PTSD trial separately excluded 90 of 324 screened participants, roughly 28 percent, on the basis of cardiovascular, bipolar-spectrum, or psychotic-spectrum criteria. The clinical implication of both data sets is that the relative contraindications act as concentrators of acute risk rather than as deterministic stops. Two relative items stacked in the same participant approach the risk profile of an absolute contraindication and warrant clinician evaluation before any session is committed to.
"The pattern across the cases that came to me for post-session triage is consistent. The participant had at least one absolute contraindication, often two relative ones, and proceeded because the operator either did not screen carefully or did screen and accepted the participant anyway. The session itself was rarely the problem. The acceptance into the session was."
The Full Contraindications Checklist
The checklist below consolidates the absolute and relative contraindications discussed across this article into a single screening filter. It is not a substitute for clinical evaluation. It is a self-screening tool to surface the questions that should be answered before any psychedelic session is committed to. If any absolute item applies, the recommendation is to not proceed outside of a monitored research protocol.
Do any of the following apply to you?
- Personal history of Bipolar I or Bipolar II disorder
- First-degree family history of Bipolar I or II
- Personal or first-degree family history of schizophrenia, schizoaffective disorder, or other primary psychotic disorder
- Currently taking lithium for any indication
- Currently taking an SSRI, SNRI, or MAOI without a medically supervised taper plan
- Uncontrolled hypertension, recent cardiac event within six months, or known ventricular arrhythmia
- Currently pregnant or breastfeeding
- Active suicidality requiring psychiatric stabilization
- Active psychotic symptoms, recent or current
- Any acute psychiatric crisis or trauma in the acute phase
Do any of the following apply, even partially?
- Active substance use disorder involving alcohol, benzodiazepines, opioids, or stimulants within the last 90 days
- Severe presentation of borderline, narcissistic, or antisocial personality disorder
- Prior episode of Hallucinogen Persisting Perception Disorder (HPPD)
- Major life crisis, bereavement, divorce, or job loss within the last 30 to 90 days
- No integration support structure available for the four weeks following the session
- No pre-session medical screening, including cardiovascular evaluation and medication review
- Current stimulant medication use (Adderall, methylphenidate) without prescribing-clinician review
- History of significant difficult psychedelic experiences without integration resolution
What Should You Do If You Match a Contraindication?
Matching one or more contraindications does not mean psychedelic work is permanently off the table. It means the next step is clinical evaluation rather than retreat booking. Across 900-plus integration sessions, the participants who navigated this well were the ones who treated a positive screen as information rather than as rejection. The sequencing that follows is concrete. Each step earns the right to the next one.
Step One: Clinician Evaluation, Not Retreat Operator
The first step is evaluation by a licensed clinician familiar with the bipolar spectrum, psychiatric medications, and psychedelic interactions where possible. This is not the retreat operator's job. Retreat operators have a financial incentive to accept participants. A clinician unrelated to the session has no such incentive. Bring the screening results from this article. Bring an honest medication list. Bring a description of your best and worst recent periods, not only the symptoms.
Step Two: Stabilize the Contraindication
If the contraindication is treatable or stabilizable, that work happens first. A recent crisis becomes a 90-day stability window. An active substance use issue becomes a sobriety arc. A medication change happens with the prescribing clinician across the medically appropriate taper window. A diagnosed bipolar presentation may lead to monitored research enrollment rather than retreat participation. The goal is not to make the contraindication invisible. It is to make the underlying condition genuinely stable.
Step Three: Choose Non-Psychedelic Pathways First
For most contraindications, especially bipolar spectrum and severe trauma in the acute phase, the appropriate next pathway is non-psychedelic and evidence-based. Lamotrigine and lithium-based protocols for bipolar depression. IPSRT and CBT for mood disorders. EMDR, somatic experiencing, and trauma-focused CBT for PTSD. Standard antidepressants and structured therapy for major depression. These pathways are slower than psychedelic-assisted approaches when those are appropriate, but they are appropriate when those are not.
Step Four: If Future Psychedelic Work Becomes Viable
If, after stabilization and clinician evaluation, psychedelic work becomes viable, the conservative path is monitored research enrollment or a clinically supervised setting rather than a retreat. The Aaronson 2024 design for Bipolar II depression is one example of what carefully monitored use looks like. Retreat contexts cannot reproduce that monitoring infrastructure. Choosing the path that matches your risk profile is the substance of good decision-making here, not the part of it that feels like delay. For deeper coverage of how to vet a retreat operator if and when you do reach that stage, see how to vet a psychedelic retreat.