[Solved] Psilocybin effect

Psilocybin is the main psychoactive component of so-called “magic mushrooms.” Chemically, psilocybin is a prodrug that is converted in the body into the active metabolite psilocin. Psilocybin itself is virtually non-psychoactive; only after conversion into psilocin can it cross the blood-brain barrier and exert its effects on the central nervous system. Below, we systematically discuss the action of psilocybin from a neurobiological perspective, its pharmacokinetics and pharmacodynamics, and its effects on the central nervous system. Therapeutic effects are not considered, so the emphasis lies on the fundamental mechanism of action of the substance.

1. Neurobiological Mechanisms

Receptor binding and neurotransmitters: Psilocin (the active form of psilocybin) acts in the brain primarily as a (partial) agonist on serotonin receptors, particularly the 5-HT_2A receptor. These receptors are Gq-coupled GPCRs that initiate a signaling cascade upon activation (via phospholipase C, IP_3/DAG, and calcium ion release). Psilocin also has an affinity for other serotonin receptors (such as 5-HT_2C and 5-HT_1A) and can indirectly modulate dopaminergic activity, but the hallucinogenic effects are mainly attributed to 5-HT_2A agonism. The 5-HT_2A receptors are abundantly present in the neocortex (including on pyramidal cells in layers III and V of the prefrontal and sensory cortex) and in high-level association areas.

Cellular effects: Activation of postsynaptic 5-HT2A receptors on cortical pyramidal cells leads to increased excitation of these neurons. Stimulation of 5-HT2A receptors has been shown to be associated with a glutamate-dependent increase in cortical pyramidal cell activity. In other words, psilocin causes additional glutamate release in the prefrontal cortex, which in turn enhances excitatory postsynaptic potentials (EPSPs) in neighboring neurons. The released glutamate also stimulates AMPA receptors on those same neurons, which increases the expression of brain-derived neurotrophic factor (BDNF). BDNF is a neurotrophin involved in neuron survival and synaptic plasticity. This molecular cascade—5-HT2A activation, glutamate release, and BDNF induction—is considered a crucial mechanism behind acute psychedelic effects. In short, on a neurobiological level, psilocin mimics the action of serotonin on 5-HT2A receptors, but in such a powerful way that neural circuits in the cortex are strongly excited and modulated. This forms the basis for the disruption of normal pattern activity in the brain during a psychedelic experience.

See also: Psychedelics and neuroplasticity 

2. Pharmacokinetics

Absorption and distribution: Psilocybin is typically ingested orally (for example, via magic mushrooms or truffles) and is well absorbed by the gastrointestinal tract. Dehydrolysis occurs in the liver and intestines via alkaline phosphatase: psilocybin loses a phosphate group and is converted into psilocin. This active metabolite reaches the systemic circulation and easily crosses the blood-brain barrier. Noticeable effects are reported within ~20 to 40 minutes after ingestion, with peak plasma levels of psilocin occurring approximately 80–90 minutes post-ingestion. For example, one study reported a peak serum psilocin concentration of ~15.6 ng/mL after ~80 minutes for a standard oral dose. Psilocin is widely distributed throughout the body and reaches the brain, where it binds to 5-HT2A receptors. The degree of receptor occupancy in the cortex depends on the dose and plasma concentration: at high doses, up to ~60–70% of the cortical 5-HT_2A receptors can become occupied. PET scans have shown that an oral psilocybin dose yields average 5-HT_2A occupancy, with the highest receptor occupancy measured in default mode network regions such as the anterior cingulate cortex and angular gyri. This receptor occupancy correlates strongly with the intensity of the subjective psychedelic experience: higher plasma psilocin levels and higher 5-HT_2A occupancy are associated with more intense effects.

Metabolism and elimination: Psilocin is further metabolized via phase I and phase II processes. An important metabolite is psilocin O-glucuronide, formed by glucuronidation in the liver. This water-soluble conjugate is the primary form in which the substance is excreted via the kidneys. The elimination half-life of psilocin in plasma averages approximately 3 hours. This means that the acute duration of action of psilocybin (as psilocin) is relatively short: most effects last 4–6 hours, which corresponds to the time required to largely eliminate psilocin. In some individuals, a prolonged elimination phase has been observed, likely due to hydrolysis (breakdown) of psilocin glucuronide, which yields free psilocin again and thus slightly prolongs the duration of action. Ultimately, the majority of the absorbed psilocin leaves the body via the urine, primarily in conjugated (bound) form. Variability in metabolism between individuals may mean that exposure to psilocin (and consequently the intensity and duration of the trip) differs per person. Factors such as gastric contents, enzyme polymorphisms, and tolerance can influence pharmacokinetics. Nevertheless, the general kinetic profile is: rapid conversion to psilocin, a relatively short half-life, and complete elimination within a few days (urine tests can detect psilocin metabolites up to ~24 hours after use).

3. Pharmacodynamics

Effects on neuronal networks: The acute binding of psilocin to 5-HT_2A receptors causes large-scale changes in brain communication and network dynamics. Resting-state fMRI and EEG studies demonstrate that psilocybin induces a wide spectrum of disorganization in the brain. For instance, the drug leads to a broad desynchronization of cortical oscillations—a decrease in normal rhythmic brain waves (e.g., reduced alpha power, 8–12 Hz) and a disruption of coherence between brain regions. In rats and humans, psilocin has been observed to cause an overall decrease in EEG power across almost all frequencies (1–25 Hz). This “chaotic” brain activity is specifically caused by 5-HT_2A receptor activation: administration of a 5-HT_2A antagonist (such as ketanserin) suppresses the characteristic decrease in functional connectivity and restores normal synchrony. In other words, the 5-HT_2A receptor is the key link responsible for the disruption of normal network integration under the influence of psilocybin.

A characteristic pharmacodynamic effect is influencing the default mode network (DMN), a brain network active during self-reflection and information integration, and associated with the sense of ego or self. Under psilocybin, the DMN exhibits reduced interconnectivity and decreased activity. fMRI studies show that normal synchrony within the DMN decreases drastically during the psychedelic state. Simultaneously, functional connectivity between normally separated networks increases. Brain imaging research, for example, shows that psilocybin reconfigures communication between the DMN and other networks (sensory, emotional), resulting in a more “disorganized” but also more flexible communication pattern in the brain. This increased global integration is accompanied by a higher entropy level of brain signals, consistent with a state shift towards more decentralized information processing (the so-called “entropic brain” hypothesis). In simpler words: psilocybin temporarily “resets” the hierarchical organization of the brain by disconnecting high-order networks such as the DMN, while lower-order sensory areas communicate more freely with each other.

See also: Default Mode Network

Synaptic plasticity: In addition to acute network disruptions, psilocybin has effects on synapses and neuroplasticity. Preclinical research suggests that psychedelics activate generic pathways that lead to the growth and strengthening of synaptic connections. Recent work in animal models demonstrated that a single dose of psilocybin can cause an increase in synaptic density within just 24 hours. In a study in pigs, an increase of ~4–5% in the density of synaptic vesicle protein (SV2A) in the hippocampus was measured one day after administration, a marker indicating more synapses or synaptic vesicles. After seven days, the synapse marker was increased even further (hippocampus +9% and prefrontal cortex +6% compared to control). These results point to persistent synaptogenesis induced by psilocybin: the brain forms new synaptic connections or strengthens existing ones, even after the substance has left the body. Simultaneously, a temporary downregulation of 5-HT2A receptors was observed: one day after exposure, the density of 5-HT2A receptors in the hippocampus and PFC was reduced, but normalized again after seven days. This phenomenon may be related to the development of tolerance in the very short term – the body adapts by internally recycling receptors after intense stimulation. Interestingly, the decrease in receptor availability may be related to the increase in synapse formation: the loss of some receptors could activate a signal cascade that promotes plasticity. Additionally, it is known that the 5-HT2A-mediated increase in glutamate (mentioned under the neurobiological mechanisms) increases BDNF, and BDNF is a key promoter of synaptic growth. In cellular models, it has been shown that classics such as psilocin stimulate the outgrowth of dendritic spines and neurites, which is consistent with these findings in vivo. In summary, psilocybin can therefore induce both acute functional changes in networks and bring the brain into a more plastic state in which structural neuronal adaptations (at the micro level) occur.

Cortical activity and sensorimotor gating: Under the influence of psilocybin, measurable parameters of cortical excitability also change. For example, magnetoencephalography (MEG) and EEG studies report a decrease in oscillatory strength in the alpha rhythm and an increase in high-frequency unstructured activity. This indicates that the cortex is in a state of heightened excitability and reduced filtering. Furthermore, psilocybin influences thalamocortical gating: normally, the thalamus filters a large portion of sensory input before it reaches the cortex, but psychedelics appear to loosen this filter, allowing more raw sensory information to reach the higher cortical layers. Although this mechanism is complex, one hypothesis is that 5-HT2A activation on deep corticothalamic neurons weakens inhibitory control, resulting in sensory overstimulation of the cortex. This potentially explains the intense sensory perceptions during a trip. In summary, the pharmacodynamics of psilocybin are characterized by dysregulation of normal network dynamics and oscillations, coupled with a state of increased neuronal plasticity and altered information processing in the brain.

4. Effects on the Central Nervous System (CNS)

Perception: Psilocybin causes pronounced changes in perception and sensory perception. Users report vivid hallucinations, both visual (e.g., moving patterns, saturated colors, seeing geometric shapes with closed eyes) and sometimes auditory. These perceptual disturbances can be traced back to excessive excitation of sensory cortices. The visual cortex (occipital lobe), in particular, undergoes abnormal stimulation: studies with related psychedelics show that increased cerebral blood flow and functional connectivity in visual areas correlate with the intensity of visual hallucinations. Under psilocybin, communication between the visual cortex and other brain regions is enhanced, which can result in synesthesia (mixing of senses, such as “hearing colors” or “seeing sounds”). At the same time, the normal top-down modulation of sensory input is weakened, allowing internal images and thoughts to seep into perception uninhibitedly. The perception of time and space is also disrupted – minutes can feel like hours, and distances and depth estimation become unreliable. These effects correspond to chaotic firing of neurons in cortical areas that normally integrate timing and spatial orientation.

Cognition: Cognitive processes under psilocybin are characterized by increased divergence and reduced linear control. People often experience a stream of thoughts that is less regulated by executive functions. This can lead to deep introspection, innovative or bizarre associations, and a feeling that thoughts can get stuck in loops. Neurophysiologically, this can be explained by the dysregulation of prefrontal networks (including the dorsolateral prefrontal cortex and part of the DMN) that normally serve as the “conductor” for thinking. Psilocybin reduces synchronization in precisely these higher-order network areas, causing thoughts to be less filtered or structured. Working memory and rational decision-making skills may be reduced under the influence, while at the same time creative, free association increases. Studies have shown that psilocybin temporarily disrupts the integrity of networks involved in cognitive control (such as the frontoparietal network), which corresponds to the subjective experience of reduced focus but increased cognitive flexibility. Interestingly enough, metacognition often occurs: users realize that their thought patterns are different from normal, which sometimes leads to insights into their own psyche or behavior (albeit not always on a reliable basis).

Consciousness and self-awareness: One of the most characteristic central effects of psilocybin is the change in state of consciousness and self-experience. Many users report a sense of ego dissolution, in which the boundaries between the self and the external world blur. One may feel as though one is “becoming one” with the environment or a universe without a clear identity of one's own. In neuroscience, this phenomenon is linked to the disruption of the default mode network. The DMN—in which the medial prefrontal cortex and posterior cingulate cortex are particularly involved—is considered the neural basis of self-reflection and the autobiographical self. Under the influence of psilocybin, activity in these regions is strongly suppressed and mutual connectivity is severed. PET/fMRI has established that psilocybin causes high 5-HT2A receptor occupancy specifically in DMN areas, which explains the subsequent functional decoupling of these hubs. As a result, the normal “neural signature” of the self disappears, which is subjectively experienced as the dissolution of the ego. Neuronal correlates of ego loss include severe desynchronization in the DMN regions and reduced communication between the hippocampus and cortex. (The hippocampus is connected to autobiographical memory and context, and its decoupling from the prefrontal cortex contributes to the loss of a continuous sense of self.) This neurobiological picture aligns with reports of a profoundly altered state of consciousness, in which one experiences, for example, feelings of spiritual unity, awe, and connectedness.

See also: Mystical experience

In addition to ego dissolution, mystical or spiritual experiences can also occur, such as the feeling of gaining insight into the “universe” or contact with a higher reality. Although the neurobiology of this is less tangible, researchers suggest that the increased global connectivity of the brain under psilocybin underlies these expanded experiences of consciousness. The brain is in a hyperassociative state in which areas that are normally not active simultaneously now temporarily fire in sync. This could generate unusual phenomenological experiences. Finally, there are emotional effects: psilocybin can trigger mood swings ranging from euphoria to anxiety, depending on the dose and context. Neuronally, these are linked to the activation of limbic structures (such as the amygdala and ACC) and the modulation of serotonergic pathways that regulate mood.

In conclusion: Psilocybin disrupts the central nervous system by acting on serotonergic receptors, thereby shifting the normal neurophysiological balance. The result is a state of increased neural firing frequency, reduced network structure, and increased openness of information circuits, which manifests as intense changes in perception, thought, and self-awareness. The aforementioned neuronal changes—for example, DMN disintegration correlating with ego loss, or glutamate increases in the cortex associated with subjective “de-boundarying”—illustrate how the psychedelic experience is closely linked to measurable changes in brain activity. This academic insight into the workings of psilocybin lays the foundation for understanding the unique consciousness-altering effects of this compound, independent of any potential therapeutic applications.

Sources: Scientific articles and reviews were consulted via AI deep research to substantiate the above-mentioned explanations, including studies on receptor binding, pharmacokinetic studies, human neuroimaging research, and preclinical studies on neuroplasticity. These sources collectively emphasize that the effect of psilocybin on the brain is an interplay of acute neurotransmission changes and subsequent neural reorganization.

See also: psilocybin information

A psilocybin experience can be profound and transformative, and therefore proper preparation and integration are essential.

Preparation for a truffle experience

• Mental and physical preparation: Ensure a clear intention and a calm mindset. Avoid stressful situations in the days before and eat light and healthy.
• Set & Setting: Choose a safe and comfortable environment and arrange for an experienced tripsitter if you are not yet familiar with this.
• Dosage: The correct dose depends on your experience and sensitivity. A supervisor can help you with the right amount.

The experience itself

During the trip, various effects may occur, such as:

• Enhanced sensory perception
• Emotional insights
• Deep introspection and self-reflection
• Mystical and spiritual experiences

It is important to accept the experience as it comes and not to resist the effects.

Integration after the experience

After the trip, it is useful to process your experiences, for example by:

• Reflection and journaling
• Conversations with a coach or therapist
• Meditation or other mindfulness techniques