THC-CBD Combination Did Not Help Alzheimer's Symptoms in Mice | Research

The takeaway

A three-week THC-CBD treatment failed to reverse Alzheimer's-related deficits in transgenic mice, and even worsened some outcomes depending on genotype.

People interested in cannabinoid research for neurodegenerative diseases, researchers studying THC-CBD combinations

0 improvement in Alzheimer's-related deficits

What the researchers found

Chronic treatment with 3 mg/kg THC and 20 mg/kg CBD did not improve anxiety-like behavior or object recognition deficits in 14.5-month-old Alzheimer's model mice. The treatment had genotype-dependent effects, causing increased anxiety in Alzheimer's mice but reduced anxiety in controls.

Why it matters

Previous research showed CBD alone could reverse some memory deficits in Alzheimer's model mice. Combining THC with CBD was hypothesized to improve outcomes, but this study found the opposite.

The numbers in context

Treatment used 3 mg/kg THC and 20 mg/kg CBD daily for 3 weeks. Alzheimer's mice showed increased anxiety-like behavior with treatment. Control females lost their normal object preference after treatment. THC-CBD significantly decreased body weight and fat deposits across all mice.

How the study worked

Researchers treated 14.5-month-old female APP/PS1 transgenic mice (Alzheimer's model) and control littermates with daily THC-CBD injections for three weeks. They tested anxiety (elevated plus maze, open field), memory (novel object recognition, Y-maze), social interaction, and sensorimotor gating.

What this study cannot tell us

Used only female mice. The THC:CBD ratio and doses may not reflect what humans use. IP injection doesn't mimic oral or inhaled routes. APP/PS1 mice don't fully replicate human Alzheimer's disease.

How to read the evidence

Preliminary: animal study using a single transgenic mouse model with only female subjects

When this study was published

Published in 2025

The bigger picture

The idea that combining cannabinoids produces better therapeutic effects doesn't always hold. Disease state appears to determine whether cannabinoids help or harm, highlighting the complexity of using cannabis-based treatments for neurodegeneration.

Questions still open

Would different THC:CBD ratios produce different results? Does the disease stage at treatment onset matter? Would male mice respond differently?

Common questions

Does this mean cannabis can't help with Alzheimer's?

Not necessarily. Previous studies found CBD alone showed some benefits in similar models. This study specifically tested a THC-CBD combination at particular doses, which didn't work and had some negative effects.

Why did the treatment affect Alzheimer's and control mice differently?

The researchers found genotype-dependent effects, meaning the disease state changed how the brain responded to cannabinoids. This suggests that what works in a healthy brain may not work in a diseased one.

Read the original research

Combination treatment with medium dose THC and CBD had no therapeutic effect in a transgenic mouse model for Alzheimer's disease but affected other domains including anxiety-related behaviours and object recognition memory.

Pharmacology, biochemistry, and behavior, 257, 174101

View on PubMed ↗Publisher’s paper ↗

Citation

Aumer, Beate; Rosa Porto, Rossana; Coles, Madilyn; Ulmer, Nina; Watt, Georgia; Kielstein, Heike; Karl, Tim. (2025). Combination treatment with medium dose THC and CBD had no therapeutic effect in a transgenic mouse model for Alzheimer's disease but affected other domains including anxiety-related behaviours and object recognition memory.. Pharmacology, biochemistry, and behavior, 257, 174101. https://doi.org/10.1016/j.pbb.2025.174101