Psilocybin's Lasting Antidepressant Effect Linked to Neuron Activity, Not Brain Structure

A new study has uncovered why psilocybin—the psychoactive compound in magic mushrooms—may provide long-lasting relief from depression. The effects appear linked to enduring changes in how neurons fire, rather than permanent structural alterations in the brain. Researchers suggest this could explain why a single dose sometimes eases symptoms for months, even in treatment-resistant cases.

The research focused on rats given a single dose of psilocybin. Five and twelve weeks later, treated animals showed fewer signs of depression-like behaviour, such as reduced immobility, compared to controls. Yet when scientists examined their brain cells, they found no lasting increase in dendritic spines—the tiny protrusions that form neural connections. This ruled out permanent structural changes as the cause.

Instead, the team discovered that psilocybin modified the intrinsic electrical properties of neurons. These shifts persisted long after any temporary physical changes had vanished. The findings suggest that activating the 5-HT2A serotonin receptor—a key target of psilocybin—may be enough to trigger these lasting electrical adjustments.

The study builds on a decade of growing interest in psilocybin's potential. Earlier trials, including those from Johns Hopkins, showed that around 70% of participants with treatment-resistant depression experienced months of relief after just one session. Current clinical trials, such as those at Charité Berlin and the Mannheim Central Institute for Mental Health, are now testing psilocybin-based therapies for legal use. Internationally, COMPASS Pathways is advancing its COMP360 formulation through Phase III trials, aiming for approval by the FDA and EMA.

One limitation of the new research is its focus on male rats. Future studies will need to include both sexes to confirm whether the effects apply broadly.

The results point to a new understanding of how psilocybin works. By altering neuronal electrical activity rather than rewiring the brain, it may offer sustained antidepressant benefits without structural changes. With ongoing clinical trials and regulatory reviews, psilocybin-based treatments could soon become a recognised option for patients who do not respond to conventional therapies.