LONDON – In a first-of-its-kind clinical trial, U.S. researchers have found that people with agitation and dementia in late life who took a special medical formulation of two active ingredients found in marijuana – THC and CBD – had significantly less agitation compared to people who received a placebo.
The primary findings of the study were presented July 14, 2026, at the Alzheimer's Association International Conference in London by Jacobo Mintzer, MD , of the and Medical University of South Carolina and Georgetown University's Brigid Reynolds, MSN, APRN, ANP-BC .
The study, dubbed the LiBBY trial (Life's end Benefits of cannaBidiol and tetrahYdrocannabinol), enrolled 120 participants with Alzheimer's disease or other types of dementia who were hospice-eligible and experiencing agitation. Ten medical centers nationwide conducted the LiBBY study visits at participants' homes or places of residence. Close to 90% of study participants who received the treatment showed overall improvement after 12 weeks.
"These trial results were extremely impressive and showed a level of response not seen before in clinical trials related to dementia. Rarely do we see close to 90% of patients in a trial respond positively to a new medication," said Mintzer, the co-lead investigator.
"Agitation affects many people with late-stage dementia, causing symptoms such as restlessness, aggression, and emotional distress that can profoundly impact patients and their caregivers," explained Reynolds, the co-lead investigator. "Current treatment options are limited and often carry significant side effects, underscoring the need for safer, more effective therapies."
Medications such as morphine, Valium and Haldol have had limited effectiveness in treating dementia-related agitation and can cause undesirable side effects.
The study was designed to evaluate the effectiveness, safety, and tolerability of a combination of purified tetrahydrocannabinol (THC) and cannabidiol (CBD) given orally in a rapid-acting digestible oil suspension. Participants were randomly assigned to receive either the active combination or placebo. To ensure unbiased results, neither the participants, their caregivers, nor the clinicians knew who received the active treatment. The mean age of participants was 80 years old.
Using a 29-factor agitation assessment survey, the Cohen-Mansfield Agitation Inventory, the researchers compared participants who received the THC/CBD mixture to those receiving a placebo at 2 weeks, the primary outcome due to the fast-acting nature of the drug, and then at 12 weeks.
Each factor related to agitation was rated on a 7-point scale from "never" to "several times per hour" by the caregivers, who were also responsible for giving the medications. After 2 weeks, there was a 6.27-point reduction in mean agitation scores in the THC/CBD group compared with the placebo group; at 12 weeks, there was a significant, sustained reduction in agitation.
A key secondary measurement was the Clinical Global Impression of Change in Behavior assessment. This analysis showed that the THC/CBD group was much less agitated at 2 weeks (83.9% vs 30.5%) and 12 weeks (87.2% vs 23.6%) compared to the placebo group. Adverse event rates, such as infections and gastrointestinal disorders, were comparable between groups (46.7% vs 42.4%) and were expected occurrences in this patient population.
Laura, whose mother participated in the LiBBY trial, said taking part in the study gave her hope that new treatment options may one day improve quality of life for families living with dementia. Although she did not know whether her mother received the study medication or a placebo, she noticed what she described as meaningful changes during visits with her. "She seemed happier," Laura said. "We experienced joy. There were still moments of connection."
Although researchers say the results of this trial are encouraging, they caution that the treatment evaluated in the trial differs significantly from commercially available THC and CBD products.
"People should not assume that products available at dispensaries or online are equivalent to what was studied in this trial," Reynolds said. "The medication used in this research was carefully formulated, manufactured, and administered under close medical supervision. Over-the-counter or commercially available THC and CBD products may vary widely in their composition, quality, and dosing, making them potentially ineffective or even harmful."
