Psilocybin Neuroimmune Connection: Beyond Serotonin

Psilocybin & Neuroinflammation

2 coordinated effects in microglia — anti-inflammatory and pro-neuroplastic

A 2025 study found psilocybin and its metabolite psilocin act on the brain's immune cells (microglia) to do two things at once: suppress the inflammatory signal TNF-alpha through serotonergic 5-HT2 and TrkB signaling, and raise BDNF, a driver of neuroplasticity, with the aryl hydrocarbon receptor (AhR) required for that plasticity effect rather than for the anti-inflammatory one.

Laabi et al., International Immunopharmacology, 2025

Microglia

the brain's resident immune cells that psilocin modulates directly via 5-HT2 receptors (Wiens 2024)

AhR

a non-serotonergic receptor required for psilocin's neuroplasticity (BDNF) effect, not its anti-inflammatory effect (Laabi 2025)

7 days

how long IL-6 and CRP stayed reduced after a single dose in a placebo-controlled trial (Mason 2023)

Laabi et al., International Immunopharmacology, 2025

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Ask most researchers why psilocybin works for depression and the answer involves serotonin. Psilocybin binds 5-HT2A receptors, disrupts entrenched patterns of brain activity, promotes neuroplasticity, and enables a window of psychological flexibility in which new emotional processing is possible. This account is well-supported and probably correct.

The question is whether it is complete.

A growing body of cellular and human evidence suggests psilocybin also engages the neuroimmune system, the network of immune cells and signaling proteins that regulates inflammation in the brain. A 2025 study found that psilocybin and its active metabolite psilocin act on microglia, the brain's resident immune cells, to do two things at once: suppress the inflammatory signal TNF-alpha and raise BDNF, a driver of neuroplasticity, through overlapping but distinguishable receptor routes.^[1] A 2023 placebo-controlled human study found that some of the immune changes produced by psilocybin were still measurable a week after the drug had cleared the body.^[4] If neuroinflammation is part of what maintains treatment-resistant depression, and psilocybin durably reduces that inflammation, then the serotonin story is missing a chapter. For the broader context of psilocybin's neuroscience, see Psilocybin and the Default Mode Network: How It Quiets the Ego.

The Standard Story: Why 5-HT2A Activation May Not Be the Full Answer

The 5-HT2A-centered explanation of psilocybin's therapeutic effects is grounded in good evidence. Psilocybin binds 5-HT2A receptors on prefrontal pyramidal neurons, changing how those neurons fire and cascading downstream through the cortico-striatal-thalamic circuit. This disrupts the rigid synchronized brain patterns that characterize depression. The resulting period of increased neural flexibility, when supported by therapeutic context, appears to enable lasting emotional and behavioral change.

The timing problem: psilocybin is metabolized and cleared from the body within hours. The antidepressant effects it produces last weeks to months. Serotonin-receptor activation alone doesn't explain this gap. Neuroplasticity is the most commonly cited bridge, specifically the structural remodeling of dendritic spines and synaptic connections that can consolidate new patterns of brain activity. But neuroplasticity itself is supported by the cellular environment around neurons, and that environment is regulated partly by the immune system.

When microglia are chronically overactivated, as they are in a subset of patients with treatment-resistant depression, they release pro-inflammatory signals that actively impair neuroplasticity. They break down the very structural bridges that psilocybin's neuroplastic mechanism depends on. If psilocybin's anti-inflammatory effects calm that microglial overactivation, it may not be a separate mechanism. It may be a prerequisite for the neuroplastic mechanism to work durably.

For the evidence on psilocybin's neuroplasticity effects specifically, see Psilocybin and Neuroplasticity: Rewiring the Brain.

Neuroinflammation in Depression: The Circuit-Level Problem SSRIs Miss

Neuroinflammation is not a peripheral or exotic feature of depression. In a significant subset of patients, particularly those with treatment-resistant cases, the brain shows measurable signs of immune dysregulation: elevated pro-inflammatory cytokines including TNF-alpha and interleukin-6, activated microglia in prefrontal and limbic regions, and disrupted trophic signaling that normally supports neuron survival and growth.

This matters for treatment in a specific way. SSRIs raise serotonin availability at the synapse. They don't substantially address the inflammatory environment surrounding the neurons they're trying to influence. A neuron receiving adequate serotonergic signaling while bathed in pro-inflammatory cytokines from overactivated microglia is operating under conflicting conditions. The serotonin says "do more of this signal." The cytokines say "reduce synaptic activity and curtail plasticity."

This conflict may explain a portion of SSRI non-response. And it raises the possibility that compounds with both serotonergic and anti-inflammatory activity could break through in cases where serotonin-only treatments cannot.

For the evidence on psilocybin's effects on TNF-alpha and systemic cytokines specifically, see Psilocybin and TNF-Alpha: Systemic Anti-Inflammatory Evidence.

Microglia and Psilocybin: A Direct Neuroimmune Link

Microglia are the brain's resident immune cells. In a healthy brain, they perform essential maintenance: clearing cellular debris, monitoring for pathogens and damage, and pruning synapses to maintain efficient neural circuitry. When chronically activated by inflammatory signals, they shift from maintenance mode to a state that amplifies inflammation and impairs the very neurons they're supposed to protect.

A 2024 study by Wiens and colleagues investigated whether psilocin, the active metabolite that psilocybin converts to in the body, directly affects microglia.^[2] The finding: psilocin modulates select neuroimmune functions of microglial cells in a 5-HT2 receptor-dependent manner. This is direct modulation, not an indirect downstream effect of changing neuronal activity patterns.

The significance of the 5-HT2 receptor dependence is worth pausing on. The same receptor through which psilocybin produces its psychedelic effects is the receptor through which psilocin modulates microglia. The therapeutic experience and the immune modulation appear to be mechanistically linked at the receptor level. They are not independent effects happening by coincidence from the same drug.

A 2024 in vitro study by Laabi and colleagues, working in cultured macrophages, established that psilocybin and psilocin have direct but context-dependent anti-inflammatory cellular properties: the anti-inflammatory effect (lower TNF-alpha, higher anti-inflammatory IL-10) appeared mainly in already-activated immune cells and belonged largely to the metabolite psilocin, while in resting cells the compounds could raise TNF-alpha instead.^[3] That specificity matters: it means blanket statements that "psilocybin is anti-inflammatory" overstate the cell data, and it set up the more precise discovery that followed in 2025. For a dedicated explanation of psilocybin's microglial effects, see Psilocybin and Microglial Modulation: Anti-Inflammatory Effects in the Brain.

The 2025 Discovery: Separating the Anti-Inflammatory and Neuroplastic Routes

The Laabi 2025 study extended the earlier cellular work in a significant direction.^[1] Working with resting and LPS-activated microglial cell cultures, the researchers measured how psilocybin and psilocin affect a pro-inflammatory cytokine (TNF-alpha), an anti-inflammatory cytokine (IL-10), and a neuroplasticity marker (BDNF), then used selective antagonists for five receptors (5-HT2A, 5-HT2B, 5-HT7, TrkB, and AhR) to work out which receptor did what.

In activated microglia, psilocybin and psilocin did two things at once: they suppressed TNF-alpha and they raised BDNF. The key contribution of the study was to separate the two effects at the receptor level. The anti-inflammatory action, the drop in TNF-alpha, was mediated by serotonergic receptors (5-HT2A, 5-HT2B, 5-HT7) and TrkB signaling. The neuroplasticity effect, the rise in BDNF, ran alongside it, and here the aryl hydrocarbon receptor mattered: AhR activation was required for psilocin's BDNF upregulation, but it was not required for the TNF-alpha suppression.

This corrects a claim that is easy to state too loosely. The accurate picture is not "AhR is a second, serotonin-independent anti-inflammatory pathway." It is that psilocybin's anti-inflammatory action in these cells runs mainly through serotonergic and TrkB signaling, while the AhR runs alongside it as a route to neuroplasticity. The study also found that IL-10, the anti-inflammatory cytokine, was unchanged under normal conditions but rose when serotonergic, TrkB, or AhR signaling was blocked, hinting at compensatory anti-inflammatory pathways the cell can fall back on.

Anchor Study

Laabi et al. (2025) · International Immunopharmacology

Population

Resting and LPS-activated microglia (in vitro)

Intervention

Psilocybin and psilocin, with selective antagonists for 5-HT2A/2B/7, TrkB, and AhR

Finding

In activated microglia, psilocybin and psilocin suppressed TNF-alpha and increased BDNF. TNF-alpha suppression was mediated by serotonergic (5-HT2A/2B/7) and TrkB signaling; AhR activation was required for psilocin's BDNF (neuroplasticity) effect but not for TNF-alpha suppression. IL-10 rose only when signaling was blocked, suggesting compensatory anti-inflammatory routes.

preliminary In vitro only, in cell cultures rather than living brains; the receptor map does not by itself establish clinical relevance.

Laabi et al., International Immunopharmacology, 2025 (RTHM-02121)

One Drug, Two Coordinated Effects

Which Receptor Does What: Anti-Inflammatory vs. Neuroplasticity

A common shortcut says psilocybin has "two independent anti-inflammatory pathways." The 2025 receptor mapping says something more precise: in activated microglia, psilocybin and psilocin lower inflammation and raise neuroplasticity at the same time, but through different receptors. The AhR sits on the plasticity arm, not the anti-inflammatory one.

Anti-inflammatory arm

TNF-α suppression — via serotonin + TrkB

In activated microglia, psilocybin and psilocin lower the pro-inflammatory signal TNF-α. Selective antagonists showed this runs through serotonergic receptors (5-HT2A, 5-HT2B, 5-HT7) and TrkB signaling. Blocking the AhR did not stop it — the AhR is not needed for the anti-inflammatory effect.

Laabi 2025 [1]; direct 5-HT2 microglial modulation established in Wiens 2024 [2] — in vitro

Neuroplasticity arm

BDNF upregulation — where AhR matters

The same treatment raised BDNF, a driver of neuroplasticity. Here the aryl hydrocarbon receptor (AhR) was required for psilocin’s effect. This is the serotonin-independent route people often misdescribe as "a second anti-inflammatory pathway" — in this study it belonged to plasticity, not to calming inflammation.

Laabi 2025 [1] — in vitro (cultured microglia)

Receptor assignments are from a single in vitro study in cultured microglia (Laabi 2025 [1]); they map a mechanism, not a clinical effect. The concentrations used in a dish may not match what reaches microglia during a supervised session, and no human study has yet linked these receptor-level effects to depression outcomes.

Mechanism map; receptor assignments from ref [1] (see references)

The clinically interesting part is what the two effects have in common: they are produced by the same treatment, in the same cells, at the same time. Calming inflammation and supporting neuroplasticity are not sequential steps but simultaneous outputs of overlapping receptor networks. That coupling, rather than the specific (and often overstated) claim of a second anti-inflammatory pathway, is what makes the finding matter for a more complete model of how psilocybin works.

The AhR is not a new discovery in pharmacology, but its role in psychedelic biology has only recently attracted attention, and the Laabi 2025 study is among the first to map its activation specifically in the context of psilocybin and psilocin.

For the brain-flexibility context of why a more dynamic neural environment matters, see Entropy and Mental Health: Why a More Flexible Brain Is Healthier.

What the Human Evidence Shows About Persisting Immune Effects

The cellular findings from Wiens 2024 and Laabi 2024 and 2025 establish mechanisms in vitro. The human evidence establishes that something measurable happens to immune status in actual people who take psilocybin.

Mason and colleagues conducted a placebo-controlled, parallel-group study in 60 healthy volunteers in which immune status was measured acutely and again seven days later.^[4] The pattern moved over time. Psilocybin immediately reduced TNF-alpha, while IL-1-beta, IL-6, and C-reactive protein were unchanged in the acute window. Seven days later, TNF-alpha had returned to baseline, but IL-6 and C-reactive protein were now persistently reduced in the psilocybin group. Crucially, participants whose IL-6 and CRP fell more at seven days reported more persisting positive changes in mood and social behavior.

The persisting seven-day changes are what matter most for the neuroimmune hypothesis. Psilocybin is metabolized completely within hours; immune markers still altered a week later represent a pharmacological footprint long after the drug itself has cleared. This is the strongest human anti-inflammatory signal in the current literature, but it must be read carefully: it is a correlation in healthy volunteers, not depressed patients, and not a demonstration that lowering inflammation caused the mood change.

DiRenzo and colleagues in 2024 are the necessary counterweight. Pooling serum from 91 participants across three prior randomized controlled trials, spanning healthy long-term meditators, people with depression, and people with anxiety and cancer, the analysis was largely null.^[5] The only statistically significant change was a transient increase in IL-8 within one week of psilocybin; there were no significant changes in TNF-alpha or IL-6, no changes at all at four weeks or later, and no significant cytokine changes when the trials were analyzed individually rather than pooled. The one signal it did detect, a short-lived rise in IL-8, points in the pro-inflammatory rather than the anti-inflammatory direction, and the authors framed peripheral cytokine production as only "possibly altered" by psilocybin.

Taken together, Mason 2023 and DiRenzo 2024 establish that psilocybin can move human immune markers, but that the size, direction, and durability of that movement are not yet consistent from study to study. The clearest persisting anti-inflammatory signal, lower IL-6 and CRP at seven days, comes from Mason's placebo-controlled trial; DiRenzo's larger pooled analysis did not replicate an anti-inflammatory cytokine effect.

Regional Specificity: Inflammatory Genes in the Reward Circuit

An animal study published in Molecular Psychiatry in 2025 added a layer of regional specificity to the neuroinflammation picture.^[6]

Floris and colleagues administered psilocybin to male rats with established heroin-seeking behavior and measured two outcomes: behavioral changes in drug-seeking, and inflammatory gene expression in two specific brain regions. The behavioral finding was that psilocybin reduced heroin-seeking. The inflammatory finding was that psilocybin modulated inflammatory gene expression specifically in the nucleus accumbens and the prefrontal cortex.

These are not arbitrary brain regions. The nucleus accumbens is the core of the brain's reward circuit, the region most directly implicated in addiction and anhedonia. The prefrontal cortex is the regulatory hub that normally exerts top-down control over reward-seeking behavior. Inflammatory dysregulation in exactly these regions has been documented in both addiction and treatment-resistant depression.

The fact that psilocybin modulated inflammatory gene expression in these specific areas, rather than producing a non-specific whole-brain immune effect, suggests the anti-inflammatory action is targeted to the circuits most relevant to the conditions psilocybin is being studied as a treatment for. This doesn't prove causality, but regional specificity is a prerequisite for a mechanism to be clinically meaningful.

The Neuroimmune Hypothesis and Why It Changes What We Think Psilocybin Does

Assembling the evidence from Mason 2023, DiRenzo 2024, Wiens 2024, Laabi 2024 and 2025, and Floris 2025 produces a hypothesis that is more complex than the standard 5-HT2A account of psilocybin's mechanism, and more complete.

The hypothesis runs as follows. In a subset of depressed patients, particularly those with treatment-resistant cases, neuroinflammation is a maintaining factor. Overactivated microglia produce pro-inflammatory cytokines that impair serotonin synthesis, reduce neuroplasticity, and degrade the neural environment that mood regulation depends on. SSRIs address the serotonin deficit they create but not the inflammatory environment driving it. This is one reason SSRIs work for some patients but not others.

Psilocybin engages both the serotonergic system and the neuroimmune system simultaneously. Its 5-HT2A activation disrupts rigid brain patterns and enables psychological flexibility. Its direct microglial modulation via serotonergic (5-HT2) and TrkB signaling reduces the inflammatory signal TNF-alpha, while a distinguishable AhR-dependent route supports neuroplasticity (BDNF) at the same time. Measured immune changes persist at least a week; the antidepressant effects persist for months. The anti-inflammatory and neuroplastic mechanisms, produced together in the same cells, may be reinforcing each other rather than operating as separate interventions.

This framing also changes how to think about who benefits most from psilocybin. If the serotonin mechanism alone were sufficient, any patient with insufficient serotonergic signaling would be a candidate. If the neuroimmune mechanism is part of what separates psilocybin from SSRIs in treatment-resistant cases, then patients with measurable inflammatory dysregulation might show the largest response.

For the specific evidence on neuroinflammation and psilocybin's anti-inflammatory brain effects, see Psilocybin and Neuroinflammation: Anti-Inflammatory Brain Effects.

Honest Limits: What This Framework Doesn't Explain Yet

The neuroimmune hypothesis for psilocybin is a well-grounded scientific argument, not a demonstrated causal pathway. Several critical gaps remain.

First, the human cytokine data are mixed and neither trial linked immune change to clinical outcome. Mason 2023 found persisting IL-6 and CRP reductions at seven days, but DiRenzo 2024, pooling three trials, found no anti-inflammatory cytokine change and only a transient IL-8 rise. Neither study measured depression outcomes in the same participants alongside the immune markers. The claim that immune changes contribute to antidepressant effects requires a study design that simultaneously measures both in the same participants and tests for mediation. No such study has been published.

Second, the cellular studies (Wiens 2024, Laabi 2024 and 2025) were conducted in isolated cell cultures, not in human brains. The concentrations of psilocybin and psilocin used in vitro may not reflect what actually reaches microglia during a clinical session, where the drug distributes across many tissues and where the blood-brain barrier modulates what enters the central nervous system.

Third, the Floris 2025 animal study was conducted in male rats with heroin-seeking behavior, a model that approximates one dimension of addiction but not the full complexity of treatment-resistant depression in humans.

These limitations don't invalidate the hypothesis. They define where more evidence is needed: human studies measuring both inflammatory and clinical outcomes in the same cohort, in vivo imaging of microglial activity before and after psilocybin treatment in depressed patients, and dose-response data connecting specific cytokine changes to specific therapeutic outcomes.

The neuroimmune connection may be part of why psilocybin works. The evidence is strong enough to take seriously and preliminary enough to hold with appropriate uncertainty.

Fact Check

Is psilocybin's antidepressant effect 'just serotonin'?

The claim

“Psilocybin works for depression entirely through 5-HT2A serotonin receptor activation.”

A common simplification of the well-supported serotonergic model of psychedelic action.

What research shows

Overstated

5-HT2A activation is central and well-supported, but it is probably not the whole story. Psilocin also directly modulates microglia via 5-HT2 receptors (Wiens 2024), and in activated microglia psilocybin suppresses TNF-alpha while raising the neuroplasticity marker BDNF (Laabi 2025). A placebo-controlled human trial found IL-6 and CRP still reduced seven days after a dose (Mason 2023).

The neuroimmune effects are real but early-stage: the human cytokine data are inconsistent (DiRenzo 2024 was largely null), the receptor mapping is in vitro, and no study yet shows that the immune changes cause the antidepressant effect.

Wiens 2024 (RTHM-02016); Laabi 2025 (RTHM-02121); Mason 2023 (RTHM-01747); DiRenzo 2024 (RTHM-01881)

Evidence Review

1. Cell studiescompleted

   Wiens 2024 (psilocin modulates microglia via 5-HT2); Laabi 2024 (macrophages) and 2025 (microglia) separate the anti-inflammatory route (serotonergic/TrkB) from the AhR-dependent neuroplasticity route.

2. Animal studiescompleted

   Floris 2025: psilocybin blunted cue-induced heroin seeking in male rats and regulated inflammatory genes (including IL-17a) in the prefrontal cortex and nucleus accumbens.

3. Small human trialscurrent

   Mason 2023 (placebo-controlled, healthy volunteers) found persisting IL-6/CRP reductions at seven days; DiRenzo 2024 (pooled sera, 91 participants) found no anti-inflammatory cytokine change. Mixed.

4. Large RCT in patientsmissing

   No adequately powered trial measures inflammatory markers and clinical depression outcomes together to test whether immune change mediates benefit.

5. Meta-analysismissing

   Too few and too heterogeneous studies to pool.

The hypothesis is mechanistically coherent and demonstrated in cells and animals, with one supportive placebo-controlled human trial. But the human evidence is mixed and no study yet shows that psilocybin's immune effects are why it improves mood.

Wiens 2024 (RTHM-02016); Laabi 2024 (RTHM-01922); Laabi 2025 (RTHM-02121); Floris 2025 (RTHM-02082); Mason 2023 (RTHM-01747); DiRenzo 2024 (RTHM-01881)

Legal & Safety

Moderate

This is research, not a treatment protocol

Concern

Psilocybin is a Schedule I controlled substance in the United States. The neuroimmune findings described here come from in vitro models, animal work, and small controlled studies; none of them establishes psilocybin as a treatment for inflammation or for depression.

What the research says

The anti-inflammatory and neuroimmune data are early, partly mixed, and largely mechanistic. No dose, formulation, or protocol for using psilocybin to modulate neuroinflammation has been clinically validated, and possession and use are illegal in most jurisdictions.

Particularly relevant for: Anyone considering psilocybin for depression or inflammation

What to do

Do not self-treat. Psilocybin for depression is currently available only through approved clinical trials and, in a small number of jurisdictions, supervised programs. Discuss depression treatment with a licensed clinician.

Not medical advice.

The Bottom Line

The neuroimmune hypothesis proposes that psilocybin's antidepressant effects are partly mediated by direct modulation of the brain's inflammatory environment, not only by serotonin receptor activation. In activated microglia, psilocybin and psilocin suppress the inflammatory signal TNF-alpha (via serotonergic 5-HT2 and TrkB signaling) while raising the neuroplasticity marker BDNF; the aryl hydrocarbon receptor (AhR) is required for that neuroplasticity effect, not for the anti-inflammatory one (Wiens 2024; Laabi 2025). Human evidence is mixed: a placebo-controlled trial found IL-6 and CRP still reduced seven days after a single dose (Mason 2023), while a pooled analysis of three trials found no anti-inflammatory cytokine change and only a transient IL-8 rise (DiRenzo 2024). The hypothesis is mechanistically coherent and supported by multiple research groups, but causal evidence in human clinical populations has not yet been published. Psilocybin is a Schedule I substance in the United States; these findings are from research settings.

Frequently Asked Questions

How does psilocybin healing work beyond serotonin?

Psilocybin appears to engage the brain's immune system alongside its well-known serotonin receptor effects. It directly modulates microglia, the brain's immune cells, through 5-HT2 receptors, and in activated microglia it suppresses the inflammatory signal TNF-alpha (via serotonergic and TrkB signaling) while raising BDNF, a driver of neuroplasticity. A separate, serotonin-independent receptor, the aryl hydrocarbon receptor (AhR), is required specifically for that neuroplasticity effect rather than for the anti-inflammatory one. In a placebo-controlled human trial, two anti-inflammatory markers (IL-6 and CRP) were still reduced seven days after a single dose, a footprint that outlasts the drug's presence in the body.

What is the neuroimmune hypothesis for psilocybin therapy?

The neuroimmune hypothesis holds that psilocybin's therapeutic effects, particularly in treatment-resistant depression, are partly mediated by its ability to modulate neuroinflammation. In a subset of depressed patients, overactivated microglia produce pro-inflammatory cytokines that impair serotonin function and neuroplasticity. Psilocybin may address this directly through microglial modulation via 5-HT2 and TrkB signaling, with a distinguishable AhR-dependent route supporting neuroplasticity at the same time. In a placebo-controlled trial, some anti-inflammatory markers were still reduced a week after dosing. This is a well-grounded hypothesis, not a confirmed causal mechanism, and the human cytokine data are not yet consistent. Studies measuring both immune and clinical outcomes simultaneously have not yet been published.

Can reducing brain inflammation heal depression?

The evidence is preliminary but consistent in direction. Neuroinflammation, specifically overactivated microglia and elevated pro-inflammatory cytokines, is measurable in a significant subset of treatment-resistant depression patients and correlates with reduced therapeutic response to SSRIs. Anti-inflammatory interventions, including certain cytokine blockers in small trials, have shown antidepressant effects in highly inflammatory patients. Whether psilocybin's specific anti-inflammatory profile is sufficient to produce clinical benefit through the inflammatory pathway alone is not yet established. Most researchers believe the serotonergic and neuroimmune mechanisms work together rather than independently.

Is psilocybin's effect on depression about more than serotonin?

The current evidence suggests yes, though the relative contribution of each mechanism is not quantified. The serotonin story, specifically 5-HT2A receptor activation, neuroplasticity promotion, and psychological flexibility during the session, is well-supported. The neuroimmune story adds direct microglial modulation of inflammatory signals like TNF-alpha and cytokine-level changes in humans. A 2025 study found that in microglia the anti-inflammatory effect and a neuroplasticity (BDNF) effect are produced simultaneously, through overlapping but distinguishable receptors, with the serotonin-independent aryl hydrocarbon receptor (AhR) required for the neuroplasticity arm. Whether these mechanisms are required for therapeutic effect, or whether one dominates in different patient subgroups, remains an active area of research.

How do microglia affect mental health?

Microglia are the brain's resident immune cells. In a healthy state, they maintain neural circuitry by clearing damaged cells, pruning unnecessary synaptic connections, and monitoring for threats. When chronically overactivated, they shift to releasing pro-inflammatory signals that damage surrounding neurons, impair the synthesis of mood-regulating neurotransmitters including serotonin and dopamine, and actively reduce neuroplasticity. Overactivated microglia are found in the brains of patients with depression, PTSD, and schizophrenia. Psilocybin appears to modulate microglial function directly, which may explain why its effects on mood and cognition outlast the drug's presence in the body.

Sources & References

1. 1RTHM-00934·Laabi, Salma et al. (2025). “Psilocybin and psilocin regulate microglial immunomodulation and support neuroplasticity via serotonergic and AhR signaling..” International immunopharmacology.Study breakdown →PubMed →↩
2. 2RTHM-00914·Wiens, Kennedy R et al. (2024). “Psilocin, the Psychoactive Metabolite of Psilocybin, Modulates Select Neuroimmune Functions of Microglial Cells in a 5-HT2 Receptor-Dependent Manner..” Molecules (Basel.Study breakdown →PubMed →↩
3. 3RTHM-00887·Laabi, Salma et al. (2024). “Deciphering psilocybin: Cytotoxicity, anti-inflammatory effects, and mechanistic insights..” International immunopharmacology.Study breakdown →PubMed →↩
4. 4RTHM-00845·Mason, N L et al. (2023). “Psilocybin induces acute and persisting alterations in immune status in healthy volunteers: An experimental, placebo-controlled study..” Brain.Study breakdown →PubMed →↩
5. 5RTHM-00874·DiRenzo, Dana et al. (2024). “Impact of Psilocybin on Peripheral Cytokine Production..” Psychedelic medicine (New Rochelle.Study breakdown →PubMed →↩
6. 6RTHM-02082·Floris, Gabriele et al. (2025). “Psilocybin reduces heroin seeking behavior and modulates inflammatory gene expression in the nucleus accumbens and prefrontal cortex of male rats..” Molecular psychiatry.Study breakdown →PubMed →↩