As global populations continue to age, conditions such as Alzheimer’s disease are becoming increasingly common. With no curative therapies available and only modest benefits from current medications, researchers around the world — including those in Brazil — have been examining alternative approaches, among them compounds derived from the Cannabis sativa plant.
A recently published Brazilian study, appearing in the Journal of Alzheimer’s Disease, investigated whether microdosed cannabis extracts containing extremely small amounts of tetrahydrocannabinol (THC) and cannabidiol (CBD) could provide cognitive benefits for older adults living with early-stage Alzheimer’s disease.
Why Researchers Are Focusing on Microdosing
The investigation, led by Professor Francisney Nascimento and colleagues at the Federal University for Latin American Integration (UNILA), enrolled older adults with mild Alzheimer’s disease and assessed the impact of daily microdoses of cannabis extract. These microdoses contained concentrations low enough to avoid the psychoactive effects associated with recreational cannabis use.
This strategy is grounded in earlier scientific evidence. Experimental research conducted in Germany in 2017 — led by Andreas Zimmer and Andras Bilkei-Gorzo — demonstrated that very small quantities of THC restored memory performance in ageing mice, partly by reversing age-related changes in gene expression and synaptic density within the hippocampus. Additional studies have since shown that the endocannabinoid system, which plays a crucial role in neural plasticity and physiological balance, gradually decreases in function during ageing.
The Brazilian research team was also influenced by a 2022 case report from their own group, in which a patient with Alzheimer’s disease showed clinical improvement after long-term microdosing of cannabis extract.
Cognitive Outcomes Observed in Brazil
The primary tool used to evaluate participants was the ADAS-Cog (Alzheimer’s Disease Assessment Scale – Cognitive Subscale), a widely recognised measure of cognitive function in dementia research. After 24 weeks of treatment, volunteers who received the microdosed extract containing THC showed stabilisation in one cognitive domain, whereas those given placebo demonstrated a decline over the same period.
The effect was modest and restricted to a specific subcomponent of the scale, but it reached statistical significance. For individuals with mild impairment, substantial improvement over short time frames is unlikely; therefore, the findings may hint at a possible protective role rather than a dramatic symptomatic reversal.
A Potential Shift Towards Non-Psychoactive Cannabis Therapies
A major barrier to broader acceptance of medicinal cannabis — particularly in older populations — remains the concern surrounding psychoactive effects. However, the approach evaluated in Brazil avoids these effects entirely, relying instead on sub-perceptual doses that still interact with biological systems involved in inflammation, neural communication and homeostasis.
Such findings contribute to an emerging view: that cannabis-based interventions need not rely on intoxication to yield therapeutic benefits. Ultra-low doses may offer a pathway for preventative strategies, especially for older adults with mild cognitive symptoms or a family history of dementia.
Important Gaps Still to Be Addressed
Despite its promising indications, the Brazilian trial has clear limitations. The sample size was small, and measurable benefit was confined to a single cognitive domain. Even so, the study represents the first clinical trial to demonstrate a statistically significant effect of microdosed cannabis extract in people with Alzheimer’s disease.
Further research is needed — including larger trials, longer follow-up periods and studies incorporating biomarkers such as neuroimaging and inflammatory markers — to determine whether cannabis microdosing might delay or prevent cognitive deterioration more broadly.
For now, the findings from Brazil offer an intriguing early step in understanding whether ultra-low-dose cannabinoids could play a role in future strategies to support healthy brain ageing.