Alzheimer's disease (AD) is closely linked to the accumulation of neurotoxins derived from Aβ and tau, leading to cognitive impairment. This project posits that an imbalance in the endocannabinoid system occurs in an AD-dependent manner. Reported connections between dementia, inflammation, Aβ, and alterations in the cannabinoid system in experimental models of AD support this hypothesis. Cannabinoids may restore baseline brain function while avoiding major side effects. Despite extensive research into new AD therapies, no significant improvement has been achieved recently, and there is little consensus on how scientists will innovate to develop a new treatment. Cannabinoid-based therapy has emerged as crucial for the treatment of many diseases considered incurable. The expected results of this project will provide important insights into the ability of cannabinoids to counteract neurochemical imbalance during AD progression, thereby improving memory performance and affecting inflammation as well as Aβ and tau levels.

The key point is to provide evidence that cannabinoids can serve as an efficient treatment for AD while avoiding major side effects. The aim of this project is to determine the effect of cannabinoids in AD patients, evaluating memory and cognition. It is expected that the results will establish that cannabinoids are critical for restoring the baseline function of the endocannabinoid system in AD brains and their beneficial effects. This project may be instrumental in validating new therapeutic approaches for AD.

To evaluate the pharmacological activity of low doses of CBD, a double-blind, randomized, placebo-controlled clinical trial will be conducted for a duration of 6 months. A baseline assessment will be performed, and patients will be evaluated every 60 days for a period of 6 months, totaling 4 evaluation sessions. For this purpose, the following questionnaires will be applied: Mini-Mental State Examination (MMSE), Neuropsychiatric Inventory (NPI), Geriatric Depression Scale (GDS), Alzheimer's Disease Quality of Life version patient, version caregiver and caregiver-patient version, Cornell Depression in Dementia Scale, and Epworth Sleepiness Scale. All questionnaires are references in their assessment domains and are validated for Portuguese/Brazil. In addition to the evaluation scales, biological material will be collected with blood and cerebrospinal fluid samples at baseline and at the end (after 6 months). The following analytes will be measured in the CSF: BDNF, beta-amyloid, Tau protein, TNFα, IL-6, IL-1β, and IL-10. During the research and data collection, patients' conventional treatments will not be altered.

Statistical Analysis Plan SPSS software, version 29.0 will be used for the analyses. For quantitative data, the Shapiro-Wilk distribution test will be performed. Potential associations between qualitative variables will be analyzed using the Chi-Square test with adjusted residual analysis (χ²). The means (±SD) will be analyzed using the Student's t test for independent samples. Medians \[IQR\] will be calculated using the Mann-Whitney U test. Paired quantitative data will be compared individually by group across the analyzed time points using Friedman's ANOVA test.

A generalized estimating equations (GEE) model, linear or with log-gamma link, and Bonferroni correction will be used to simultaneously evaluate quantitative parameters over time and between groups. For these descriptive analyses, data will be presented as means ± standard errors (±SEM). Pearson or Spearman correlations can be performed between variables of interest. For all analyses, the significance level will be set at 5%.