Neuroplasticity and Psychedelics: How They Rewire the Brain

What Is Neuroplasticity?

Neuroplasticity is the brain's ability to form new neural connections, reorganize existing networks, and adapt its structure in response to experience. It underlies learning, memory, recovery from brain injury, and the capacity to change behavioral and emotional patterns. Neuroplasticity is highest in childhood and declines with age, though it never disappears entirely.

How Psychedelics Promote Neuroplasticity

Research has identified several mechanisms through which psychedelics enhance neuroplasticity:

Dendritic Spine Growth

A landmark 2018 study by Ly et al. published in Cell Reports demonstrated that LSD, psilocybin, and DMT promote the growth of dendritic spines, the small protrusions on neurons where synaptic connections form. This effect, termed psychoplastogenesis, was observed across multiple cell types and was comparable in magnitude to the effects of ketamine, which is already known to rapidly promote synaptogenesis.

Importantly, these structural changes persisted well beyond the acute psychedelic effects, suggesting that the neuroplasticity window opened by psychedelics extends for days to weeks after a single dose.

BDNF and Neurotrophic Factors

Psychedelics increase the expression of brain-derived neurotrophic factor (BDNF), a protein essential for neuronal survival, growth, and synaptic plasticity. BDNF acts as fertilizer for the brain, supporting the growth and maintenance of neurons. Chronic stress and depression are associated with reduced BDNF levels, and many antidepressant treatments increase BDNF over time. Psychedelics appear to do this more rapidly and robustly.

Default Mode Network Disruption

The default mode network (DMN) is a brain network active during self-referential thinking, mind-wandering, and rumination. In depression, the DMN becomes hyperconnected and rigid, trapping individuals in repetitive negative thought patterns. Psychedelics acutely reduce DMN connectivity while increasing communication between brain regions that do not normally interact. This disruption may create a window of enhanced flexibility during which rigid cognitive and emotional patterns can be revised.

The REBUS Model

The Relaxed Beliefs Under Psychedelics (REBUS) model, proposed by Carhart-Harris and Friston, offers a unified framework. It suggests that psychedelics relax the brain's high-level predictive models, the entrenched beliefs and assumptions that normally constrain perception and cognition. This relaxation allows new patterns to form, new perspectives to emerge, and rigid pathological patterns to be overwritten.

Clinical Implications

The neuroplasticity hypothesis explains several clinical observations: why the therapeutic effects of psychedelics often outlast the acute experience by months, why the combination of psychedelic-induced neuroplasticity with psychotherapy produces better outcomes than either alone, and why the period immediately following a psychedelic experience is considered a critical window for integration and behavioral change.

Comparison With Other Neuroplasticity-Promoting Interventions

Exercise, meditation, learning new skills, and sleep all promote neuroplasticity, but on different timescales and through different mechanisms. Psychedelics appear to provide a rapid, concentrated burst of plasticity that may accomplish in hours what other interventions achieve over months. This does not make them superior, but rather complementary. The combination of psychedelic-assisted therapy with ongoing practices that support neuroplasticity, such as exercise, meditation, and therapy, may produce the most robust and lasting outcomes.