A Critical Evaluation of the Hypothesis that N,N-Dimethyltryptamine Maintains Neuroplasticity

The brain’s ability to rewire itself, neuroplasticity, declines dramatically with age. Children learn faster; adults get stuck in patterns; older adults struggle to adapt. The reasons for this decline remain unclear. In a companion paper (Solis, 2026a), I critically evaluated the broad hypothesis that N,N-dimethyltryptamine (DMT) has endogenous physiological functions. The evidence was found to be mixed and contested. This paper narrows the focus to a specific, testable hypothesis: that DMT may play a role in maintaining neuroplasticity, and that its decline may contribute to the age-related loss of cognitive flexibility. DMT is known to promote synaptic growth, neurogenesis, and BDNF expression in animal models. DMT levels are reportedly highest during development and decline with age. However, the evidence is mixed and contested. Barker (2025) reports DMT concentrations in the nM range, comparable to serotonin and dopamine. Palner et al. (2026) report that DMT is below the detection limit in rat brain. The sigma-1 receptor affinity (Ki ~14 μM) is three orders of magnitude higher than reported physiological concentrations. The intracellular 5-HT2A receptor finding (Barker 2025) has not been independently replicated. The dietary DMT gap has not been directly measured. Clinical trials demonstrate that high-dose DMT produces antidepressant effects (Erritzoe et al. 2026; Falchi-Carvalho et al. 2025), but clinical efficacy does not establish endogenous function. The paper does not claim the hypothesis is established; it critically evaluates the evidence and proposes a research program to test whether DMT depletion is a cause of lost plasticity, or whether the relationship is incidental.