Canada’s SAP Expansion Signals a Step Forward for Psychedelics

By Dr. Rakesh Jetly

Health Canada’s recent SAP revision brings a new opportunity for patients and a clear responsibility for prescribers.

Health Canada’s recent decision to include psychedelic medicines in its Special Access Program (SAP) was met with a lot of fanfare. The SAP amendment brings good news for certain patients – specifically, treatment-resistant patients suffering from serious mental health conditions that impact individuals, families, and communities.

The new federal amendment has the potential to fill a critical gap for patients in need, including those suffering from depression, PTSD, and end-of-life anxiety. Many who suffer from mental health conditions don’t respond fully to current treatments, so there is a significant unmet need for safer and more effective therapies. The change to Health Canada’s SAP now allows physicians, clinics and hospitals to apply for previously restricted drugs for medical use, providing a new option for the patients who need it most.

I applaud the federal government for responding to the grave situation of the patients who aren’t responding to otherwise adequate treatment – and for recognizing the encouraging clinical data around psychedelic-assisted therapy. This SAP revision represents one small but important step on the road to greater access to psychedelic medicine.

Like most opportunities, this one comes with considerable responsibility. Failure to act responsibly could cause harm to individuals and to this evolving area of medicine. However, I believe that the community of experts in psychedelic medicine are ready and willing to support the practitioners who will be administering these therapies to patients.

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What Does the SAP Revision Provide?

Health Canada’s SAP revision adds certain psychedelics, including MDMA and psilocybin, to the list of restricted substances that practitioners can request to treat patients in specific situations. Decisions will be made on a case-by-case basis, and will be reserved for serious treatment-resistant or life-threatening conditions, in instances where other therapies have failed, or are unsuitable or not available in Canada.

The recent amendment reverses regulatory changes made almost a decade ago that prohibited access to restricted drugs (including psychedelics). Historically, practitioners in Canada have been able to apply for unlicensed medications only through Health Canada’s Section 56 exemption – a fairly long and restrictive process. The SAP revision is expected to provide a much quicker review and more rapid access for approved patients.

Obviously, the SAP amendment will not bring broad access to psychedelic medicine in Canada, but ideally will help treatment-resistant patients, and serves as a clear signal that the government is acknowledging the potential of psychedelic medicine as a legitimate treatment option.

Celebrate the Progress, Continue the Push for Approval

To me, the government’s decision to include psychedelics in Canada’s SAP is a key acknowledgement that mental health conditions are being placed on the same footing as physical conditions, and frankly, that’s a shift that’s long overdue. Anyone working in mental health can see that treatment-resistant mental illness is indeed a serious or life-threatening condition, analogous to cancer that hasn’t responded to conventional treatment. But mental health disorders aren’t always viewed with that sense of urgency.

I’ve dedicated a good part of my medical career to raising awareness and advocating for changes in the treatment of mental health issues. I spent more than 30 years as a medical officer and psychiatrist in the Canadian Armed Forces, deploying twice and leading mental health programs in Afghanistan. I served as mental health advisor to the Canadian Forces surgeon general, and led initiatives with Canada and NATO as we explored innovative solutions in mental health. Achieving change in attitudes toward mental health and treatment innovation requires considerable effort and persistence. 

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We’ve seen modest improvement in mental health care over the years. However, I firmly believe we need to do better in this arena. Far superior advances have been made in the treatment of cancer, heart disease, and many other conditions that take an enormous toll on society and represent a significant  medical and economic burden. 

Yet in the field of mental health, so many patients continue to suffer without adequate or effective treatment. We must review the data while being mindful that each file or data point represents a person who is struggling. We must work to develop medicines with better results, realizing that mental health disorders affect not only patients, but their families and loved ones, their careers and communities.

During my time as the Chief of Psychiatry, I have experienced firsthand the enormous impact that trauma can have on soldiers and veterans. From mass graves in Rwanda to the battlefields of Kandahar, it’s difficult to see people who are putting their lives on the line to protect their country return home to treatments that will only work for half of them. 

So the onus is on us to look for better solutions, to refuse to be satisfied with the status quo and to embrace ALL positive steps forward. In Canada, the inclusion of psychedelics in the SAP is one of those steps. That’s progress worth celebrating. 

A growing body of evidence continues to demonstrate that psychedelic-assisted psychotherapies are emerging as a successful treatment option in many indications, from treatment-resistant depression to smoking and alcohol addiction to PTSD, anxiety, and OCD. 

In the area of smoking cessation, Dr. Matthew Johnson and his team at Johns Hopkins are planning new studies to build on his team’s ongoing research, including the first government-funded clinical study in 50 years evaluating a psychedelic for therapeutic use. The team’s earlier study reported that 80% of participants who received psychedelic-assisted therapy remained abstinent from smoking at 6 months and 67% remained abstinent at 12 months. Those encouraging results show strong efficacy, and demonstrate clear progress.

We see positive data in other indications as well, including PTSD. MAPS is currently sponsoring MAPP2, the second of two Phase 3 trials studying MDMA-assisted therapy for PTSD. In the first Phase 3 study, 88% of participants with severe PTSD experienced a clinically-significant reduction in PTSD diagnostic scores two months after their third session of MDMA-assisted therapy, compared to 60% of placebo participants. Additionally, 67% of participants in the MDMA group (compared to 32% of participants in the placebo group) no longer met the criteria for PTSD remission two months after the sessions.

When governmental and regulatory agencies endorse the positive early results of new, transformative treatments, we can celebrate this success. And when organizations dedicate funding for continued research in our field, we applaud those decisions. We can use every bit of incremental progress as adrenaline to keep gathering evidence, and to use that evidence as our guide as we expand treatment options and promote best practices in administering them.

Setting Up Providers and Patients for Success

As Canada implements its recent change, the responsibility lies with clinicians and regulatory bodies to be very deliberate and safe in the way we use the SAP program. We must ensure that patient selection is based on science, and principles such as informed consent are followed. 

I encourage doctors and patients considering these new treatment modalities to review the available research and have open, honest conversations with one another to determine if psychedelic-assisted psychotherapy is right for them. These are far from being first-line treatments and we must continue to turn to approved evidence-based treatments first. 

Here’s the government’s process for requesting drugs through the SAP:

To administer psychedelic-assisted therapy under Health Canada’s SAP, healthcare professionals must fill out an application, which will be reviewed on a case-by-case basis.

The SAP considers a “healthcare professional” someone who:

  • is entitled, under the laws of a province or territory, to treat patients with an unapproved prescription drug
  • practices in that province or territory
  • has prescribing privileges in the respective province

Practitioners who receive approval can then request products from manufacturers that meet governmental requirements.

A few examples of questions asked in the application:

“What specifically about this drug makes it the best choice for your patient(s)?”

“Specify all treatments tried and/or failed…”

A request to provide references/evidence:

A question for a request for a repeat patient:

The final section:

How progressive or cautious will Health Canada be in reviewing and approving requests? That remains to be seen. But as a physician, my advice is clear: The practitioners who seek permission to use these medicines should ensure that they have the necessary training, competence, and confidence to provide these treatments safely and successfully. 

The innovators in our field are scientists, doctors, and advisors offering extensive experience with psychedelic compounds, as well as mental health and addiction disorders. We must step up and support physicians who want to prescribe these treatments, but who might not have experience implementing psychedelic-assisted psychotherapy. We can provide evidence-based research, education on proper protocols, and access to experienced psychedelic integration specialists to answer questions every step of the way. 

My message is simple: Let’s do this right. Let’s do this safely. 

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The End Goal: Regulatory Approval and Integration into Clinical Practice

The SAP should not be considered an alternative to integrating psychedelic-assisted therapy into existing medical practices. Rather, it provides help for those who qualify for use in exceptional circumstances under the SAP guidelines. It’s a step forward, but it’s not a solution.

Psilocybin and MDMA-based therapies are successful with specific indications and patient profiles. We need to continue gathering data to demonstrate safety and efficacy through clinical trials targeting specific indications. That’s the path to obtain regulatory approval of psychedelics with therapy protocols. Psychedelics must undergo the same rigor as any other medication vying for approval from regulatory bodies. We need to continue the work that will lead to an environment of safe, regulated access to psychedelic therapy in a medical setting. That takes patience, but will pay off in the long run.

Ultimately, the millions of patients afflicted with serious mental illness will benefit most when they have access to more advanced, more effective therapies than those on the market today. We truly see success when medical communities view psychedelic medicine as an accepted and adopted form of treatment within our existing healthcare infrastructure. 

About the Author

Dr. Rakesh Jetly is Chief Medical Officer at Mydecine Innovations Inc., where he leads the company’s scientific research and clinical trials. He is the former Chief of Psychiatry for the Canadian Armed Forces, retiring in 2021 as a colonel after 31 years of service. Dr. Jetly served as senior psychiatrist and mental health advisor to the Canadian Armed Forces Surgeon General. He is an associate professor at Dalhousie University (Halifax) and the University of Ottawa. During his career, Dr. Jetly has led initiatives within Canada and NATO to better understand and innovate solutions in the mental health field. He has published extensively on topics such as PTSD, suicide, leveraging technology in mental health, and occupational psychiatry.

How Can We Apply Harm Reduction to HPPD?

By Ed Prideaux

In last week’s blog, Ed Prideaux told us everything we know (and don’t) about Hallucinogen Persisting Perception Disorder (HPPD), visual snow syndrome, and flashbacks. In part 2, he addresses ways to deal with the distress of having HPPD and ways to reduce the risk of developing it in the first place.

The real “problem” with HPPD is distress: anxiety, depression, isolation, panic, and the unhelpful coping mechanisms people can develop to overcome these (alcoholism and drug dependency are sadly common among HPPD patients). Remember, this distress is what technically defines HPPD.

Many people live with significant visual changes and do not find them distressing – rather, they may be sources of enjoyment, “free trips,” artistic inspiration, or purposefully leaned into as part of spiritual or occult practice. The world looking different doesn’t necessarily mean you have a problem. 

If you’re currently experiencing HPPD, though, overcoming the distress should probably be your first priority. Speaking crudely, once the distress is overcome, the visuals can more or less “take care of themselves.” With less distress, there is less fixation. With less fixation, there is less noticing. With less noticing, the visuals are less noticeable. They may rapidly normalize, filter in the background, and can disappear unexpectedly with time.

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How Can We Address This Distress – and Bring the Visuals Down?

Medication and clinical help:
Many in the HPPD community have found relief in the use (especially in the short-term) of medications including Lamotrigine and Klonopin. They can bring visuals and anxiety way down, though some report their symptoms getting worse. They can always bring side effects, too, so some caution is advised.

Do not be surprised, either, if clinicians have not heard of HPPD. It is little-known and poorly-understood. It may be useful to refer your clinician to the Information Guide included on the Perception Restoration Foundation’s website.

Healthy lifestyle changes:
Many HPPD patients report the decline and resolution of their symptoms – or otherwise acceptance and returning to “normal” life after avoiding further drug-taking, exercising regularly, cutting out processed foods, or trying specific elimination diets.

Noting Triggers: 
Pay attention to your triggers and act accordingly. Visuals and other HPPD symptoms can surface in response to:

  • Fatigue
  • Stimulation, including caffeine 
  • Anxiety and stress
  • The nature of the environment: visuals are more apparent in the dark, on blank surfaces, in enclosed rooms, and in environments where people had their original psychedelic experiences
  • Specific foods 
  • Fixation and attention, including staring at blank surfaces and an anxious tendency to look out for visuals 
  • Intoxication with other drugs, especially cannabis 

You should also pay special attention to how your condition manifests beyond visuals, in particular, if you are experiencing Depersonalization/Derealization Disorder. More than visuals, it’s often the case that people’s distress comes from DP/DR, and a rich body of literature and therapeutic approaches have been explored for this condition. 

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Community: You can seek community from others, such as groups on Facebook, or the forums at, r/HPPD, or r/visualsnow. However, tread cautiously around spending too much time on these forums. They can be extremely negative, and cause people to spiral and fixate on their perceptual changes.

Mindfulness meditation: The stress reduction and relaxation effects of meditation are well-established; many report breaking the cycle of visual fixation through learning to hone their attention.

Cognitive techniques: Cognitive Behavioral Therapy (CBT) and Acceptance and Commitment Therapy (ACT) may be useful for accepting and reframing perceptual changes. Challenging the internal beliefs triggered by HPPD could reduce both distress and the visuals – in particular, the beliefs that patients are “brain damaged,” “weird,” “isolated,” or a “casualty.”

Psychedelic integration: Introspection, journaling, and (if you can find and afford it) specialist, psychedelic-informed counseling can be helpful. In particular, you may benefit from exploring the particular details and events of what may have caused HPPD to originally materialize.

Somatic approaches: Certain somatic/bodily therapies have proven helpful for people with Visual Snow Syndrome. This includes the use of acupuncture, muscle relaxation techniques, neck massage, and specific dietary interventions.

Reframing: It may be helpful to learn that many people are not troubled by their perceptual changes. Again, they can be just a “thing” – how one sees now – that’s different, and not necessarily bad. Other people actively enjoy their perceptual changes or view them in a spiritual way, such as glimpsing auras, having broadened the possibility of the mind, or in seeing the intrinsic shakiness of ordinary experience.

Without a deep, embodied grounding for your reframing, though, it can be hazardous. Make sure the frame is not just “in your head,” but truly held across your entire mind and body in a felt way. Don’t gaslight yourself into enjoying your perceptual changes if they are actually disturbing you.

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How Can One Reduce the Risk of Developing HPPD When Taking Psychedelics?

There is reason to suspect that the immediate period after a trip – say, one-to-five days – is important. This is because the brain is still neuroplastic and affected by psychedelics for up to a week (or longer) after the trip. And HPPD may be understood as a problem of “resetting” one’s brain back into its ordinary perceptual categories after the shock of a psychedelic experience.

If you want to avoid HPPD, what matters is ensuring that your perception re-transitions to its prior sober state safely. In this one-to-five day period, it may be advised, then, to:

  1. Sleep well.
  2. Avoid cannabis and further drug-taking. Some people report that their HPPD was “kicked in” by a subsequent drug experience.
  3. Process the psychedelic experience through dedicated integration practices, such as journaling, contemplation, meditation, and inquiry. Speaking very crudely – and because HPPD may well be a “network disorder” involving cross-connected mixtures of perception, emotion and cognition – it may be that failing to integrate the experience may cause the energy to remain and be reactivated, including in cognition and possibly in perception (especially if the right triggers are also hit).
  4. Keep stress and anxiety to a minimum.
  5. Re-embodiment, or reconnecting to body sensations. Practices may be recommended, including through mindfulness meditation. This may help to reduce the risk of dissociative disorders like Depersonalization/Derealization as well.
  6. Reduce screen use. Focusing on screens may cause a disembodying effect, as well as holding back the psychological energies activated by the psychedelic experience.
  7. Avoid triggering environments, such as places that are enclosed or rich in blank surfaces, and try not to self-induce visuals through staring and fixation. If someone wants to be extra careful, they may wish to avoid the place where they had their psychedelic experience. “Training” the brain in hallucinatory ways of seeing while it’s neuroplastic may cause lingering changes once neuroplasticity is reduced and stable categories are reaffirmed.

Important Questions to Ask Before Having an Experience

Have you optimized your set and setting?
HPPD seems to be more likely after bad trips or challenging experiences – the likelihood of which strongly depends on how people organize their set and setting. In particular, stress and trauma going into a psychedelic experience may be a trigger for HPPD experiences, even at low dose (and microdose) levels.

Have you experienced some unusual visuals before?
HPPD patients may have had a higher-than-normal experience of certain visual oddities, which are rare parts of normal perception. In particular, phenomena like visual snow, halos, after-images, floaters, and colors in the dark may suggest an underlying tendency in perception that could be triggered by a psychedelic drug to be more intense.

Have you tested your drug? If so, what drug are you taking?
HPPD may be more likely with Novel Psychoactive Substances (NPSs) and Research Chemicals (RCs) with more unpredictable, less-researched, and possibly neurotoxic effects. Adulterants in street drugs may also have neurotoxic and other risky properties.

It seems that long-acting psychedelics like LSD are more likely to cause HPPD. While LSD may have certain advantages over other psychedelics subjective to each user, someone very conscious of developing HPPD (at least compared to other risks) may wish to avoid LSD in favor of a shorter-acting psychedelic.

How often are you tripping?
Taking lots of psychedelics frequently is likely to be correlated with a higher risk of developing HPPD. This can be explained in a number of ways:

  1. A higher likelihood of having a bad trip
  2. Activating a latent genetic susceptibility 
  3. More likely to over-excite relevant perceptual circuits
  4. More “re-training” of perception in hallucinatory ways of seeing
  5. Less time in which to integrate properly one’s experiences, and a possibility of a “cascade” of neuroplasticity from taking psychedelics while still in a neuroplastic state

    Do you have experience of Obsessive Compulsive Disorder (OCD), Autism Spectrum Disorder (ASD), Complex PTSD, Generalized Anxiety Disorder (GAD), or Attention Deficit (Hyperactivity) Disorder (ADD/ADHD)?
    While there has not been research on the relationship of HPPD to these conditions, reviews of online forums directly and indirectly suggest a relationship. People with Visual Snow Syndrome seem to experience these conditions more than average based on rough overviews, and people with these conditions may independently report certain visual changes similar to HPPD. If there is a relationship between HPPD and these conditions, the connection may occur through tendencies towards disembodiment, hypersensitivity, overstimulation, and dissociation, all of which may have visual components – and may be amplified by psychedelic experience.  

For more, this article’s tips, advice, analysis (and more) is also featured in a more in-depth HPPD Information Guide, which can be freely downloaded from the Perception Restoration Foundation’s website, where a more direct guide for those struggling with HPPD is also hosted. Owing to the tentative nature of our HPPD knowledge base, the PRF invites any and all comments and criticisms for the Guide at, and any worthwhile amendments will be quickly published.

About the Author

Ed Prideaux is a UK-based writer and journalist who’s written about psychedelics for the BBC, VICEThe Independent, and Unherd, and other topics for The Guardian, The Financial Times, The Spectator, and The Quietus. Ed is working to advocate and raise awareness around Hallucinogen Persisting Perception Disorder (HPPD) in affiliation with the Perception Restoration Foundation, a new 501 (c) (3) nonprofit that has secured the launch of HPPD’s first breakout studies in decades.

More from Ed Prideaux:

HPPD and Flashbacks: Everything You Need To Know – And What We Don’t Know, Too

By Ed Prideaux

Hallucinogen Persisting Perception Disorder, or HPPD, is among the more mysterious, debilitating, and under-researched possibilities of psychedelic drug-taking. As enthusiasm around psychedelics and their possible benefits continues to grow, it’s imperative that researchers, user populations, and clinicians look closely at HPPD and other possible hazards.

HPPD is little-known among clinicians, and many reporting these experiences have trouble finding informed help. Treatments – pharmacological, psychotherapeutic, and somatic – are out there, and by reports, have proven useful for some, but no controlled trials have been performed to gauge their true effectiveness. 

In this article – intended as an exercise in harm reduction, raising awareness, and ensuring true informed consent before people ingest psychedelics – we’ll outline the current knowledge base around HPPD, including indications of the gaps and where future research may prove useful. This article’s tips, advice, and analysis (and more) is also featured in an in-depth HPPD Information Guide, which can be freely downloaded from the Perception Restoration Foundation’s website, where a more direct guide for those struggling with HPPD is also hosted.

The HPPD Basics: What is it?

Hallucinogen Persisting Perception Disorder is a DSM-5 listed condition in which people experience lasting, distressing changes to their perception after taking psychedelic drugs. There are two types: Type-1, in which people experience episodic (usually sudden) “flashbacks,” and Type-2 (the more commonly reported), in which people’s everyday perception is altered.

These perceptual changes may be married with shifts in cognition, mood, and somatic experience, and further research is required to understand how they relate. HPPD can last anywhere from weeks and months to several years – some people live with its perceptual changes for decades. In up to 50% of HPPD patients, the changes may spontaneously remit within five years.

The perceptual changes are wide-ranging, but most constellate around a stable set of experiences also reported in other conditions: Visual Snow Syndrome (VSS), migraine with aura, manic episodes, epilepsy, anxiety disorders, brain injuries, and also as experienceable features (under the right conditions) of normal, healthy perception.

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This implies that HPPD likely sits on a continuum with other disorders and ordinary perception. Further research is required to understand HPPD’s role in this continuum, the possibly unique contribution of psychedelics in affecting symptoms, and the kinds of treatments people with HPPD would benefit from versus other disorders. 

  • Visual snow: When the field of vision is coated with small, grainy dots like the static of a detuned TV
  • Haloes and starbusts: When objects have a bright “halo” or “aura” ring around them, or concentric colored rays around light sources
  • Trails: When an object moves, a trail of faint replicated images follows it
  • After-images: When the outline or silhouette of an object is seen on a surface after looking away
  • Enhanced hypnagogia, or the semi-visionary state experienced between waking and sleep
  • Intensified floaters: Most of us have seen “floaters,” which are the small squiggly lines and shapes that sometimes appear in our vision. With HPPD, these floaters can become more visible, disturbing, and irritating
  • Blue Field Entoptic Phenomenon: The appearance of tiny bright dots moving quickly along squiggly lines in the visual field, especially when looking into bright blue light such as the sky
  • Changes to size and depth perception: Things can seem smaller, at-a-distance, expanded, or possessing a two-dimensional quality
  • Assorted psychedelic-style effects: Fractal kaleidoscopic and geometric patterns, faces, “breathing” walls, moving, “wavy” or shaky text, flashing and strobing lights, closed-eye visuals, enhanced phosphenes
  • Complex pseudohallucinations 

Other, non-perceptual symptoms are reported, too:

  • Physical effects, such as head pressure, acute neck pain, unequal pupil sizes, muscle twitches
  • Tinnitus and ringing of the ears
  • More intense dreams
  • Auditory changes
  • Confused and unclear thoughts, including brain fog, trouble processing information, memory loss, dyslexia, and the onset of stammering
  • Depersonalization/Derealization Disorder (DP/DR), in which people feel detached from their bodies and the world stops feeling real
  • Psychosis
  • Anxiety, depression and panic 

Note, to be diagnosed with HPPD, these changes must prompt distress – which they do, in many cases. They can disrupt people’s everyday function – relationships, work, operating heavy equipment, driving, navigating the day-to-day, and beyond – and cause anxiety, panic attacks, depression, and suicidal thoughts in high numbers of clinical patients. Many report a strong degree of isolation and loneliness, and the disorder is also strongly-correlated with dissociative experiences like Depersonalization/Derealization Disorder (DP/DR). 

How Common is HPPD?

We don’t know. It seems that developing perceptual changes after taking psychedelics is not necessarily that uncommon; the distressing, intrusive kind that manifests in HPPD is likely a real but minority experience. 

A 2011 survey of 2,455 users of psychedelics (via Erowid) found that up to three-fifths of psychedelic users reported lingering changes, 25% in ways that were seemingly permanent, and 4.2% in ways so distressing that they could prompt seeking clinical help. The latter is suggestive of diagnostic HPPD. 

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What Kinds of Psychedelics Are Implicated?

Practically every psychedelic, but some more than others: LSD, psilocybin, ayahuasca, 2-CB, ibogaine, etc., but also related (but not classically psychedelic) drugs like MDMA, cannabis, dextromethorphan (DXM), datura, ketamine, salvia, and diphenhydramine (DPH) have been implicated. 

In anecdotal reports and the existing literature, it seems that LSD is the leading cause of perceptual changes compared to other kinds of drugs. Whether this is because LSD has been historically the most commonly-used psychedelic or there is something special to the LSD experience or its effect on neurophysiology is unclear. Short-acting psychedelics like DMT seem to be less implicated. 

Some report that, after heavy use of classic psychedelics, their HPPD developed suddenly after the use of research chemicals like 25-i-nBOME, which is often mis-sold as LSD; HPPD is also reported in particular among users of synthetic cannabinoids. Cutting agents in street MDMA, including synthetic cathinones (“bath salts”), may make HPPD more likely.

Can Non-Psychedelic Drugs Create These Perceptual Changes?

Yes. SSRI antidepressants, antibiotics, antipsychotics, and nootropics have been described in self-reports as triggering very similar visual changes. There is also considerable overlap between HPPD/post-psychedelic perceptual changes and another drug-free condition known as Visual Snow Syndrome (VSS). 

At the same time, compared to other drug classes, it seems that psychedelics (in particular, LSD) provide a higher risk factor for developing these perceptual changes. It may also be that HPPD patients report different kinds of visuals (perhaps more psychedelic ones), or more cognitive and emotional changes (as with psychedelics’ powerful psychoactive effects), compared to non-psychedelic groups.  

Is HPPD the Same Thing as Flashbacks? Aren’t Flashbacks a Myth?

It’s complicated. The “flashback” describes a particular kind of experience in which people feel they truly re-live a prior psychedelic state: something that is real and can happen, and is what people may experience in Type-1 HPPD. Most cases of Type-2 HPPD, though, will likely not be true examples of flashbacks in this way.

To give a brief overview, the idea that psychedelic drugs could cause lasting changes in perception was noted from as early as 1954 – 15 years before the notion of the “flashback” was ever coined. A number of authors in the first wave of psychedelic research from the 1950s to the early 1960s reported patients experiencing a wide range of complications after their drug experiences – including what sounds like standard HPPD – but also states that blur more into psychosis and the experience of complex pseudohallucinations. They noted that some patients were acutely re-living their trips.

These observations continued once psychedelics became popular drugs of adult use in the mid-to-late 1960s. This was reported in popular media from, at latest, 1966. 

The “flashback” label was coined by author Mardi J. Horowitz in 1969, and used for many years afterwards, including by Dr. Henry Abraham, who first developed the psychiatric diagnosis of HPPD. Perhaps contrary to what we’d expect, authors in the “flashback” literature were at pains to emphasize the complexity, variation, and need for further research in explaining the phenomenon, as well as noting that many (some surveys suggested the majority) did not find their experiences distressing.

The Flashback Problem

Unfortunately, the idea of the flashback was later sensationalized by journalists and prohibition activists, who tied the idea to certain marked untruths: that the drug can be “stored” in the spine or fat cells, make people legally insane, or otherwise cause major brain damage.

The flashback idea also had some conceptual problems, which is perhaps to be expected from the first attempts at describing a new phenomenon. With some critical exceptions, authors were bound by a consensus that post-psychedelic visuals and flashbacks were re-experiences of the visuals glimpsed in the psychedelic state – as if the drug had not properly worn off, perhaps as a matter of lasting changes to neurological function. The notion that HPPD is a “re-experiencing” has also become one of the core criteria of the current DSM-5 diagnosis.

As noted earlier, though, identical perceptual phenomena can be experienced both through non-psychedelic drug classes, and as part of experiences in which drugs played no necessary role: other kinds of neuropsychological conditions, or otherwise as a feature of normal perception. 

In contemporary literature, some authors have noted that many patients experience visual effects that never manifested in their trips – though this isn’t the case for everyone. Those who are “reliving” their trips may be described plausibly as experiencing flashbacks.

The idea of the flashback is also not unique to psychedelics – in particular, it’s used as a descriptor for experiences of post-traumatic stress disorder (PTSD), in which people can feel “flung back” to the original trauma in quasi-visionary states. This implies that the psychedelic “flashback” may not be a distinct phenomenon for some (or most) cases: rather, that it’s an example of a psychedelic drug-induced traumatic flashback, where the real issue is trauma (not drugs per se).

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How Do We Explain What’s Going On?

Since authors first noticed that psychedelics can cause lingering changes in perception, a variety of different hypotheses have been pursued to explain what’s going on. The HPPD experience will likely involve a complex, multi-factor origin that varies from patient to patient.  

Could psychedelic experiences alter neurophysiological function?

HPPD’s leading neurophysiological hypothesis, introduced by Dr. Henry Abraham, relates the condition to a “disinhibition” of the visual cortex. Drugs like LSD decrease, or “disinhibit” the filters of the brain’s visual cortex, so visual noise that would otherwise be filtered out may remain in the field of vision. HPPD occurs when these filters do not return to their pre-drug state. This may make HPPD akin to a form of “visual tinnitus” (and tinnitus is also experienced as a symptom).

This disinhibition is linked to reductions in alpha waves in the brain. A neuroimaging study by Abraham (2001) suggested that alpha wave frequency increases with HPPD patients versus controls. The role of an objective alteration to visual perception was lent support by 1982 and 1988 studies executed by Abraham, in which he found both non-HPPD LSD users and HPPD patients had decreased ability to discriminate color differences and light sensitivity during dark adaptation, with HPPD patients reporting further decreased ability.

There could be a role for neuroplasticity, or neurons’ ability to change and reform in response to experience. This may be explained in the context of a “Bayesian Brain” model, similar to the REBUS and entropic brain hypotheses introduced by UCSF’s Robin Carhart-Harris: by shaking the “snowglobe” of our nervous system’s categories of perception through a psychedelic experience (or psychoactive changes altogether), it could be that those categories do not settle as before. A neuroplasticity model may explain why, in some cases, further psychedelic experimentation can reduce or eliminate HPPD presentation. It may underlie also why teenagers are especially vulnerable, as they have more plastic, developing brains.  

LSD’s long duration may explain why the drug is so associated with HPPD – that is, with more hours of seeing abnormal visual changes, the brain is more likely to reprogram itself than with shorter-acting drugs. Smokeable DMT, for instance, isn’t particularly-associated with perceptual changes, while longer-acting ayahuasca is.

Synaptogenesis may also be involved. As described by Samuel Štancl, “Psychedelics induce strong synaptogenesis, or the creation of new synapses, resulting in high synaptic density. EEG scans show less inhibitory activity in the visual cortex both in people on psychedelics and in people with HPPD.” This means that electrical currents are being enhanced in the visual cortex by increased synaptic connection. This also underwrites why pruning excessive synapses through pharmacological treatments like lithium – or even exercise – may be useful.

What about psychological factors?

A 2018 paper by Halpern and Passie suggested that challenging drug experiences, including intense reactions of panic, dysphoria, anxiety and trauma, may be associated with a higher likelihood of developing HPPD. This is more likely for psychedelic use in uncontrolled settings. 

Recall, HPPD often co-arises with Depersonalization/Derealization, a dissociative reaction in which people feel disconnected from their bodies and immediate environments. This is suggestive of anxiety and trauma. Drug-free anxiety and depersonalization are independently-associated with similar, if not identical, perceptual changes. Somatic cognitive changes, including head pressure and brain fog, are also associated with anxiety. Challenging and traumatic drug experiences may therefore induce elevations of anxiety, which has its own uncharted pathway towards many changes, including perception.

In the historical flashback literature, there was tentative evidence that visual phenomena could be experienced as matters of attention, hypnotization, and placebo suggestion. The role of trait absorption – or a person’s tendency to become occupied by mental imagery and internal experience, including daydreaming, fantasy and hypnagogia – has also been discussed by authors as a possible personality determinant of HPPD likelihood.

Check out our course on the Jungian concept of the “shadow” and the many ways it applies to psychedelics, “Psychedelics and the Shadow: Exploring the Shadow Side of Psychedelia.

What’s more, there are case reports of people altogether resolving their distress and visuals through targeted psychotherapies without pharmaceuticals: in particular, Cognitive Behavioral Therapy (CBT) to target the destructive internal beliefs people formed around their condition (“I am brain damaged,” “I’m a weirdo,” “I’m a freak,” etc.), including in combination with relaxation techniques. The sense of isolation may also be addressed through the therapist leaning into their own capacity for abnormal visual phenomena, and experiencing them with the patient – something that resolved one person’s HPPD.

Psychedelic researcher Stanislav Grof explained and resolved his patients’ cases of HPPD through psychodynamic therapies. He interpreted HPPD as a problem of the psychedelic surfacing unconscious material that needed to be re-integrated through additional encounter experiences, including with psychedelics and breathwork.

Could HPPD patients simply be noticing more stuff that previously filtered into the background?

Yes, at least for some patients. Phenomena like visual snow, after-images, tinnitus, and floaters are not necessarily uncommon, even among “normal” people. As a possibly overlapping mechanism with anxiety and fixation, it may be that some people with HPPD are noticing perceptual features that had previously been filtered into the ignorable background of their experience. Halpern and Passie found that HPPD patients were possibly more likely to have experienced visual oddities before they took drugs.

This led Krebs and Johansen to recommend re-attributing some HPPD experiences to Somatic Symptom Disorder, whereby people fixate and ruminate on normal somatic experiences and perceptions.

This is unlikely to be exhaustive, because many HPPD patients report florid and extreme visual changes that plausibly could not have been ignored before; it will also have limited applicability to those whose visuals are distinctly psychedelic and are experiencing Type-1 HPPD. It’s possible, too, that histories of such visual experiences imply a vulnerability that has been activated or catalyzed by drug experiences. 

Part 2 of this article, focusing on harm reduction, will be posted shortly!

This article’s tips, advice, analysis (and more) is also featured in a more in-depth HPPD Information Guide, which can be freely downloaded from the Perception Restoration Foundation’s website, where a more direct guide for those struggling with HPPD is also hosted. Owing to the tentative nature of our HPPD knowledge base, the PRF invites any and all comments and criticisms for the Guide at, and any worthwhile amendments will be quickly published.

About the Author

Ed Prideaux is a UK-based writer and journalist who’s written about psychedelics for the BBC, VICEThe Independent, and Unherd, and other topics for The Guardian, The Financial Times, The Spectator, and The Quietus. Ed is working to advocate and raise awareness around Hallucinogen Persisting Perception Disorder (HPPD) in affiliation with the Perception Restoration Foundation, a new 501 (c) (3) nonprofit that has secured the launch of HPPD’s first breakout studies in decades.