What to Expect: A Guide to Psilocybin Therapy Side Effects
Understanding the full spectrum of what happens during psilocybin therapy—both expected and unexpected—can mean the difference between a transformative experience and an overwhelming one. While research consistently shows that psilocybin-assisted therapy is remarkably safe when conducted properly, knowing what side effects might emerge helps patients prepare mentally and physically for their sessions.
The Physical Experience: What Your Body Might Feel
The physical side effects of psilocybin are generally mild and temporary, but they're worth understanding before your session. Most people experience some combination of pupil dilation, changes in blood pressure and heart rate, nausea (particularly in the first hour), and alterations in body temperature perception. You might feel unusually warm or cold, even when the room temperature hasn't changed.
Some patients report headaches either during or after sessions, while others notice muscle tension or weakness. Dizziness can occur, especially when standing up quickly. These physical sensations typically peak within the first two hours and gradually subside as the session progresses. The nausea, while uncomfortable, is rarely severe and often diminishes once the psychological effects begin in earnest.
Interestingly, research using the Swiss Psychedelic Side Effects Inventory has documented that many physical side effects are dose-dependent and vary significantly between individuals. What feels manageable to one person might feel more pronounced to another, which is why having experienced facilitators present matters so much.
The Psychological Journey: Navigating Intense Emotions
The psychological effects during psilocybin sessions can be profound and sometimes challenging. Many patients experience what researchers call "psychological flexibility"—a kind of mental loosening that allows new perspectives to emerge. But this same quality can sometimes feel destabilizing.
Anxiety often appears early in sessions, sometimes described as a "come-up anxiety" as the substance begins to take effect. This typically resolves within 30-60 minutes, though for some patients it may persist longer or return in waves. Fear can emerge, particularly when encountering difficult memories or emotions. Some people experience transient paranoid thoughts, though these are generally recognized -even in the moment- as substance-induced rather than believed literally.
Emotional intensity is perhaps the most universal psychological effect. Patients commonly report crying, laughing, feeling overwhelming love or grief, or experiencing multiple emotions simultaneously. This emotional amplification is often considered therapeutic rather than problematic—it's precisely this emotional access that makes the therapy effective for conditions like depression and PTSD.
Confusion and difficulty with logical thinking are normal during peak effects. Your usual cognitive processes may feel altered or temporarily inaccessible. This is expected and temporary, which is why having guides present to help orient you matters tremendously.
The Challenging Experience: When Things Get Difficult
Not every moment of psilocybin therapy feels pleasant or manageable. What therapists call "challenging experiences" occur in a significant minority of sessions—perhaps 20-30% depending on how they're defined. These aren't necessarily bad outcomes; often the most difficult sessions yield the most therapeutic benefit afterward.
A challenging experience might involve intense fear, feelings of losing control, disturbing imagery, or confrontation with painful memories or emotions. Some patients temporarily lose their sense of self or experience what feels like dying or going crazy. While terrifying in the moment, these experiences typically resolve completely as the session ends.
Research has identified several factors that increase the likelihood of challenging experiences: higher doses, insufficient preparation, uncomfortable physical settings, lack of trust in facilitators, and pre-existing anxiety about the session. Importantly, having a challenging experience doesn't mean the therapy has failed—proper integration work afterward can transform these difficult moments into meaningful insights.
The key distinction is between a challenging experience and a genuinely dangerous one. Proper screening, preparation, and monitoring keep genuinely dangerous situations extremely rare. Your facilitators are trained specifically to help you navigate difficult moments without intervention unless safety requires it.
After the Session: What Happens Next
The immediate aftermath of a psilocybin session—the first few hours after effects subside—often brings fatigue and emotional sensitivity. Many patients feel mentally and physically exhausted, similar to how you might feel after an intensely emotional conversation or experience. This is normal and expected.
In the days following sessions, some people experience what's sometimes called an "afterglow"—a period of enhanced mood, openness, and mental clarity. Others notice emotional vulnerability or continued processing of material that emerged during the session. Both patterns are normal.
A small percentage of patients experience transient headaches, difficulty concentrating, or sleep disturbances in the 2-3 days post-session. These typically resolve without intervention. More concerning but rare are persistent perceptual changes or prolonged psychological distress, which is why follow-up integration sessions are considered essential parts of responsible therapy protocols.
Long-Term Safety: What the Research Shows
When examining longer-term effects, psilocybin's safety profile remains remarkably strong—particularly when compared to the landscape of conventional psychiatric treatments and their associated risks. Crucially, psilocybin is not habit-forming or addictive. Unlike many substances used in mental health treatment, it doesn't create physical dependence, doesn't trigger withdrawal symptoms when discontinued, and doesn't lead to compulsive use patterns that characterize addiction.
This absence of addictive potential represents a significant advantage, especially for patients who have experienced dependency issues with other medications or substances. Psilocybin doesn't activate the brain's reward pathways in ways that drive repeated use, and research consistently shows that people don't develop cravings or tolerance requiring escalating doses. In fact, the intensity of the experience itself tends to discourage casual or frequent use—this is medicine that commands respect rather than inviting dependence.
Beyond its non-addictive nature, psilocybin doesn't cause the organ damage, metabolic disruption, or cognitive impairment associated with long-term use of many psychiatric medications. The vast majority of adverse effects are acute—occurring during or immediately after sessions—rather than persistent. Patients don't face the common burdens of daily medication side effects like sexual dysfunction, weight gain, or emotional blunting that often accompany conventional treatments.
However, there are important exceptions for specific populations that must be acknowledged. People with personal or family history of psychotic disorders face elevated risks of triggering or worsening psychosis. Those with certain cardiovascular conditions may experience problematic blood pressure or heart rate changes during sessions. Pregnant or breastfeeding individuals should avoid psilocybin entirely, as effects on fetal and infant development haven't been adequately studied.
The research also suggests that proper screening and preparation dramatically reduce risk. The adverse events documented in clinical trials—which use rigorous protocols—are notably less frequent and severe than those reported from uncontrolled or recreational use. This underscores how therapeutic context and harm reduction frameworks fundamentally shape outcomes, offering a model for how medicine should be administered with both efficacy and safety.
Preparing for Your Experience
Understanding potential side effects isn't meant to frighten you but to prepare you. Most people navigate psilocybin sessions without significant difficulty, particularly in therapeutic settings with proper support. The patients who tend to have the smoothest experiences are those who:
Trust their facilitators and the process
Have done thorough psychological preparation
Understand that challenging moments may arise and are temporary
Stay curious rather than resistant when difficult material emerges
Remember that their facilitators are there specifically to help with whatever arises.
Your preparation sessions should include detailed discussion of what you might experience and how you'll be supported. Don't hesitate to ask questions about anything that concerns you. The more prepared you feel, the more able you'll be to surrender to whatever the experience brings.
Putting Side Effects in Perspective
When evaluating psilocybin therapy side effects, context matters enormously. Compared to conventional psychiatric treatments—which often require daily dosing with ongoing side effects like sexual dysfunction, weight gain, or emotional blunting—psilocybin's acute, session-limited side effects profile looks quite favorable for many patients.
The research shows that most people who complete psilocybin-assisted therapy rate their experiences as among the most meaningful of their lives, despite—and sometimes because of—challenging moments during sessions. The temporary discomfort of side effects is generally considered worthwhile given the potential for lasting therapeutic benefit.
This doesn't mean side effects should be dismissed or minimized. They're real, sometimes intense, and deserve serious consideration. But understanding them as normal parts of a therapeutic process, rather than signs of danger or failure, helps patients approach treatment with appropriate expectations and confidence.
Let us support you in your exploration of psilocybin-assisted therapy in Colorado. Our experienced practitioner provides safe, legal, evidence-based treatment in a supportive environment. Contact us for the answers to your questions: Contact Kykeon
Citations
Calder, A. E., & Hasler, G. (2024). Validation of the Swiss Psychedelic Side Effects Inventory: Standardized assessment of adverse effects in studies of psychedelics and MDMA. Journal of Affective Disorders, 365(1), 258-264.
Johnson, M. W., Griffiths, R. R., Hendricks, P. S., & Henningfield, J. E. (2018). The abuse potential of medical psilocybin according to the 8 factors of the Controlled Substances Act. Neuropharmacology, 142, 143-166.
MacCallum, C. A., Lo, L. A., Pistawka, C. A., & Deol, J. K. (2022). Therapeutic use of psilocybin: Practical considerations for dosing and administration. Frontiers in Psychiatry, 13, Article 1040217.