Does Cannabis Worsen Memory or Cognition in Dementia?

PostedMarch 12, 2026

UpdatedMarch 12, 2026

ByMy Patient Advice

Author: Julia Sutton, MSc | Reviewed by: Dr. Clarissa Morton, PharmD

As medical cannabis gains attention for managing agitation and sleep issues in dementia, one critical question remains: could it worsen memory or cognition? Both THC (tetrahydrocannabinol) and CBD (cannabidiol) interact with brain systems involved in learning and memory. While CBD may offer neuroprotective benefits, THC can impair cognitive function, especially in older adults with existing memory decline. Current research advises caution in using cannabis for people with dementia.

How Cannabis Affects the Brain

Cannabis acts on the endocannabinoid system, which helps regulate memory, mood, and brain signalling.

THC binds to CB1 receptors in the hippocampus and cortex, regions responsible for short-term memory and focus. High or frequent doses can reduce attention, reaction speed, and recall.

CBD works differently. It has anti-inflammatory and antioxidant effects that may protect brain cells and counteract some of THC’s impairing effects.

A 2024 review in Frontiers in Psychiatry (PubMed 38447959) found that THC can temporarily impair memory and executive function, particularly in older adults, while CBD alone did not worsen cognition. Similarly, the BMJ 2021 review (BMJ, 2021) reported that cannabinoid use was linked to mild cognitive slowing, though effects were dose-dependent and reversible after discontinuation.

What Studies in Dementia Show

Evidence from dementia-specific trials is limited but consistent:

The STAND trial (UK, 2025) using a THC: CBD spray showed no improvement in cognition, though most participants maintained stable cognitive scores (PMC12143470).

In a Swiss feasibility study (2022), mild confusion was reported in some patients receiving THC: CBD oil (PubMed 36247984).

A CBD-dominant oil trial found no adverse cognitive changes and small improvements in anxiety and behaviour (PubMed 36148467).

Overall, studies suggest that THC-heavy products may impair cognition, whereas CBD-dominant oils appear neutral or protective.

NICE And NHS Guidance

According to NICE guidance NG97 and NICE NG144, cannabis-based medicinal products are not recommended for treating dementia due to limited evidence and potential cognitive side effects. The NHS also cautions that cannabis can cause confusion, memory problems, and slowed thinking, especially in older adults.

Clinical Bottom Line

THC may worsen short-term memory and attention in dementia.

CBD appears cognitively safe and may offset THC’s effects.

Evidence remains limited, with small sample sizes and short durations.

NICE and NHS do not recommend cannabis for cognitive or behavioural improvement in dementia.

Educational Context: AlleviMed

AlleviMed provides educational information about the regulation of cannabis-based medicines under MHRA and Home Office oversight. It clarifies that cannabis is not approved for cognitive symptoms in dementia.

Takeaway

While CBD-based products appear safe, THC can impair memory and attention in people with dementia. According to NICE and NHS, cannabis should not be used to treat cognitive symptoms. Further long-term research is needed before cannabis can be considered safe for brain health in dementia.

Julia Sutton, MSc

Author

Julia Sutton is a clinical psychologist with a Master’s in Clinical Psychology and experience providing psychological assessment and therapy to adolescents and adults. Skilled in CBT, client-centered therapy, and evidence-based interventions, she has worked with conditions including depression, anxiety, bipolar disorder, and conversion disorder. She also has experience in child psychology, conducting psycho-educational evaluations and developing tailored treatment plans to improve learning and well-being.

All qualifications and professional experience stated above are authentic and verified by our editorial team. However, pseudonym and image likeness are used to protect the author's privacy.

Dr. Clarissa Morton, PharmD

Reviewer

Dr. Clarissa Morton is a licensed pharmacist with a Doctor of Pharmacy degree and experience across hospital, community, and industrial pharmacy. She has worked in emergency, outpatient, and inpatient pharmacy settings, providing patient counseling, dispensing medications, and ensuring regulatory compliance. Alongside her pharmacy expertise, she has worked as a Support Plan & Risk Assessment (SPRA) officer and in medical coding, applying knowledge of medical terminology, EMIS, and SystmOne software to deliver accurate, compliant healthcare documentation. Her skills span medication safety, regulatory standards, healthcare data management, and statistical reporting.

All qualifications and professional experience stated above are authentic and verified by our editorial team. However, pseudonym and image likeness are used to protect the reviewers's privacy.