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Can Cannabis Worsen Confusion or Delirium in Dementia? 

Posted
Updated
ByMy Patient Advice
Author: Julia Sutton, MSc | Reviewed by: Dr. Clarissa Morton, PharmD

Confusion and delirium are common in dementia and can be triggered by infections, medications, or changes in the environment. As cannabis is increasingly explored for managing agitation and sleep problems, concerns remain about whether THC or CBD might worsen confusion or trigger delirium in older adults. Current evidence suggests that THC can increase cognitive disorientation, while CBD appears safer and may even help stabilise mood and anxiety. 

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How Cannabis Affects Cognition 

Cannabis acts on the brain’s endocannabinoid system, which regulates memory, alertness, and attention. 

  • THC, the psychoactive compound, binds to CB1 receptors in the hippocampus and cortex, brain areas responsible for learning and orientation. In older or cognitively impaired adults, this can exacerbate confusion, sedation, and short-term memory loss. 
  • CBD, in contrast, interacts with serotonin (5-HT1A) and CB2 receptors, which may promote calmness without impairing alertness. 

A 2024 review in Frontiers in Psychiatry (PubMed 38447959) found that high-THC products were linked to temporary confusion and cognitive slowing, particularly in older adults. The BMJ 2021 review (BMJ, 2021) reported that sedation and disorientation were among the most frequent side effects of THC-containing formulations. 

Evidence From Dementia Studies 

The STAND trial (UK, 2025) found that balanced THC: CBD sprays were generally well tolerated but caused mild confusion and drowsiness in a few participants (PMC12143470). In a Swiss feasibility study (2022), using THC: CBD oil, several patients experienced transient disorientation that resolved with dose adjustment (PubMed 36247984). A CBD-dominant trial (Avidekel, 2022) reported no worsening of confusion and noted improved calmness in some participants (PubMed 36148467). 

Collectively, the data suggest that CBD formulations are cognitively neutral, while THC-rich products can temporarily intensify confusion or sedation in dementia patients. 

NHS And NICE Guidance 

According to NHS guidance, medical cannabis may cause confusion, drowsiness, and slower thinking, especially in older people. The NICE NG97 dementia guideline and NICE NG144 both state that cannabinoids are not recommended for dementia due to limited safety and efficacy evidence. The Alzheimer’s Society also warns that cannabis may worsen confusion in vulnerable individuals. 

Clinical Bottom Line 

  • THC can cause short-term confusion, drowsiness, and delirium-like symptoms. 
  • CBD appears safe and may help reduce agitation without impairing clarity. 
  • NICE and NHS caution against cannabis use in dementia due to cognitive side effects. 
  • Confused or frail patients should be monitored closely if prescribed cannabinoids. 

Educational Context: AlleviMed 

AlleviMed educates on medical cannabis regulation in the UK, explaining how products are prescribed under MHRA and Home Office oversight. It clarifies that cannabis is not approved for confusion, delirium, or cognitive symptoms in dementia. 

Takeaway 

THC-rich cannabis can worsen confusion or trigger mild delirium in dementia, while CBD-based formulations appear safer. According to NHS and NICE, cannabis should be used only under specialist supervision, with careful monitoring for cognitive changes. 

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. 

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