Study data published in JAMA Network Open outline the potential adverse effects of therapeutic delta-9-tetrahydrocannabinol (THC) use in older adults. In a meta-analysis of the literature, THC exposure was associated with increased incidence of dizziness and light-headedness in adults over the age of 50 years. THC exposure was also associated with thought or perception disorders, including dissociation.

While the association between THC exposure and psychotic symptoms is well-documented in adolescents and young adults, the precise relationship in older adults is unknown. To clarify the potential side effects of THC exposure in older adults, investigators conducted a systematic review of randomized controlled trials (RCTs) reporting the safety and efficacy of different cannabinoid-based medicines (CBMs) in adults over the age of 50 years. Studies published prior to November 2020 were eligible for inclusion.

The outcomes of interest were any adverse event experienced during exposure to CBMs. Pooled effect sizes were estimated for each adverse event and expressed as incident rate ratios (IRRs). The relationship between THC or cannabidiol (CBD) dose and adverse event severity was examined separately using meta-regression analyses.

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A total of 30 studies assessed the effects of THC-only CBMs on a total of 1417 individuals. Mean age in the pooled cohort was 59.5 years, and 53.0% were men. Additionally, investigators identified 24 studies that described the effects of the combination of CBD and THC. The pooled cohort from these studies comprised 1917 patients (mean age, 58.2 years; 49.5% men).

In pooled analyses of THC-only studies, a significant dose-response relationship was observed between THC and dizziness and lightheadedness. At a dose of 10 mg/d, the IRR of dizziness or lightheadedness was 2.04 (95% CI, 1.51-2.75). At a dose of 20 mg/d, this IRR increased to 3.33 (95% CI, 2.43-4.58).

THC exposure was also associated with increased risk for thinking or perception disorders, including dissociative disorders, in THC-only studies. Specifically, at doses of 10 mg/d and 20 mg/d, the IRRs for thinking or perception disorders were 1.92 (95% CI, 1.32-2.80) and 3.84 (95% CI, 2.27-6.50), respectively. No other neuropsychiatric adverse events were significant in pooled analyses.

In this large-scale analysis of CBMs, higher THC exposure in older adults was associated with increased incidence of dizziness, lightheadedness, and certain psychiatric symptoms. These associations were present only in RCTs assessing THC rather than trials examining the combination of THC and CBD.

Further study is needed to better elucidate the potential side effects of therapeutic CBMs in older adults, particularly those older than 65 years of age. Additionally, the use of self-report metrics for adverse events — rather than medical records data — may have introduced bias.

“[T]hese results indicate that THC-containing CBMs should be used cautiously in those aged 50 years or older, especially considering that dizziness or light-headedness may increase the risk of falls among older adults,” the investigators wrote.

Disclosure: A study author declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.


Velayudhan L, McGoohan KL, Bhattacharyya S. Evaluation of THC-related neuropsychiatric symptoms among adults aged 50 years and older: A systematic review and metaregression analysis. JAMA Netw Open. 2021;4(2):e2035913. doi:10.1001/jamanetworkopen.2020.35913.

This article originally appeared on Psychiatry Advisor