Prescribed Medical Cannabis Had Minimal Impact on Cognitive Performance in Patients | Research

The takeaway

In a semi-naturalistic trial of 40 medical cannabis patients, standard doses of prescribed cannabis did not impair cognitive performance on validated tests, with some measures actually improving, though vaporized flower produced more subjective "stoned" feelings than oils.

Medical cannabis patients concerned about cognitive effects and clinicians advising on daily functioning

No cognitive impairment found

What the researchers found

Participants' performance improved over time on the CANTAB Multitasking Test and Rapid Visual Information Processing test. No significant impairment was found on any cognitive measure. Vaporized flower produced stronger subjective feelings of being "stoned" and "sedated" compared to oils. Chronic non-cancer pain and sleep disorders were the most common indications.

Why it matters

Previous cannabis cognition research primarily studied recreational users. This study suggests that medical cannabis patients using prescribed doses may experience minimal cognitive impairment, which is important for patients concerned about functioning at work or while caring for family.

The numbers in context

40 patients (22 female); mean age 41.38; mean 10.18 months of MC use; oils (n=23): 9.61mg THC/9.15mg CBD; flower (n=17): 37mg THC/0.38mg CBD; improved multitasking and rapid visual processing; no impairment on any measure

How the study worked

Semi-naturalistic, open-label trial with 40 patients (22 female) prescribed medical cannabis for various conditions. Patients self-administered their standard prescribed dose in the laboratory. Cognitive performance assessed with CANTAB and Druid app before and after cannabis use. Subjective effects rated on visual analogue scales.

What this study cannot tell us

Open-label design means patients knew they were receiving cannabis. No placebo control group. Small sample of 40 patients. Practice effects could explain improved scores on repeated testing. Patients were experienced users with established tolerance.

How to read the evidence

Semi-naturalistic design reflecting real-world use, but open-label with no placebo and small sample with established tolerance

When this study was published

2023 study

The bigger picture

Tolerance development may explain why established medical cannabis patients show minimal cognitive effects at their prescribed doses. This supports the idea that patients can develop stable medication regimens that do not compromise daily functioning.

Questions still open

Would cannabis-naive patients show cognitive impairment at the same doses? Is the lack of impairment due to tolerance or to genuinely low doses? Would driving-specific assessments show different results?

Common questions

Does medical cannabis make it harder to think?

In this study of 40 experienced patients using their regular prescribed doses, no cognitive impairment was detected. Some measures actually improved, possibly due to practice effects or symptom relief improving baseline function.

Is there a difference between oils and vaporized flower for cognitive effects?

Cognitive test scores did not differ between the two, but patients who vaporized flower reported feeling significantly more "stoned" and "sedated" than those using oils, likely due to higher THC doses and faster onset.

Read the original research

A Semi-Naturalistic, Open-Label Trial Examining the Effect of Prescribed Medical Cannabis on Neurocognitive Performance.

CNS drugs, 37(11), 981-992

View on PubMed ↗Publisher’s paper ↗

Citation

Arkell, Thomas R; Manning, Brooke; Downey, Luke A; Hayley, Amie C. (2023). A Semi-Naturalistic, Open-Label Trial Examining the Effect of Prescribed Medical Cannabis on Neurocognitive Performance.. CNS drugs, 37(11), 981-992. https://doi.org/10.1007/s40263-023-01046-z