- This single-site randomized trial evaluated the effect of obtaining a medical marijuana card on certain clinical symptoms and cannabis use disorder (CUD) in 186 adults with a chief concern of chronic pain, insomnia, anxiety, or depressive symptoms
- The participants were randomly assigned to acquire a medical marijuana card immediately (n=105) or to be placed on a waiting list to get a card (n=81)
- The group that received a card had a higher incidence of CUD diagnosis within just 12 weeks (adjusted OR, 2.88; 95% CI, 1.17–7.07; P=0.02), and the rate was even higher among those who obtained a card because of anxiety or depressive symptoms
- The participants who obtained a card for pain, anxiety or depressive symptoms had no significant reduction in symptoms versus those who were delayed in obtaining a card, but people treating insomnia had significant improvement in self-reported symptoms
- A medical marijuana card may pose a high risk or may even be contraindicated for people with mood disorders, whereas cannabis deserves future in-depth research for its effects on insomnia
36 U.S. states and the District of Columbia allow residents to obtain a medical marijuana card and use cannabis to treat a variety of health concerns. But in a randomized trial, Massachusetts General Hospital researchers found ownership of a medical marijuana card was associated with an almost tripled risk of developing cannabis use disorder (CUD) within just 12 weeks.
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In their report in JAMA Network Open, Jodi M. Gilman, PhD, director of neuroscience in the Center for Addiction Medicine (CAM) at Mass General, Randi M. Schuster, PhD, director of neuropsychology at CAM, and colleagues add that participants who sought a medical marijuana card because of anxiety or depressive symptoms were at especially high risk of CUD.
The researchers conducted the single-site trial between July 1, 2017, and July 31, 2020. Individuals were eligible if they were 18 to 65 years old and sought medical marijuana to improve pain, insomnia, or symptoms of anxiety or depression. Importantly, exclusion criteria included daily use of cannabis, a CUD diagnosis, or another current substance use disorder (except mild or moderate alcohol use disorder or nicotine use disorder).
269 participants were randomly assigned to obtain a medical marijuana card immediately or to be put on a waiting list for 12 weeks. Participants from both groups could choose their cannabis products, dose, and frequency of use. Those who obtained their cards used cannabis products from a dispensary with the required medical oversight.
All participants had in-person visits at the start of the study and two, four, and 12 weeks later. At all those time points they completed questionnaires and provided urine samples. A researcher telephoned each participant at week 8 to inquire about adverse events.
The primary outcome measures were the:
- CUD symptom checklist of the DSM-5 (score range 0–11, with higher scores indicating more severe CUD)
- Hospital Anxiety and Depression Scale
- Brief Pain Inventory, severity subscale
- Athens Insomnia Scale (score range 0–24, with higher scores indicating more severe sleep difficulties)
186 individuals (66% women, average age 37) completed the first study visit and at least one other visit and were included in the analyses. 105 obtained their card before the first study visit and 81 were waitlisted.
The primary results were:
- CUD symptoms—Significantly greater in the group that had their cards (average difference in score between groups, 0.28 points; P<0.001)
- Anxiety—No significant difference between groups
- Depressive symptoms—No significant difference between groups
- Chronic pain—No significant difference between groups
- Insomnia symptoms—Significantly reduced in the group that had their card (average difference in score between groups, −2.90 points on a self-reported insomnia scale; P<0.001)
Incidence of CUD
During the 12-week trial, 17% of individuals in the group that already had their cards were given a CUD diagnosis at one or more study visits. In the waitlisted group, that figure was 9%.
Once the researchers accounted for other factors that can influence the development of CUD, the group that already had their cards was at nearly three times higher risk of CUD (adjusted OR, 2.88; 95% CI, 1.17–7.07; P=0.02).
Rates of CUD were even higher in the subgroup of patients who wanted a medical marijuana card because of anxiety or depressive symptoms. 13 of 46 participants (28%) already had their cards versus four of 37 participants (11%) in the delayed card acquisition group who developed CUD.
No participant who received their cards displayed an increase in psychotic symptoms, mania, hypomania, suicidal ideation, or suicidal behavior during the trial.
Key Takeaway Messages
For healthcare professionals and the public alike, the key messages from this trial are:
- People with anxiety or depressive symptoms who had access to cannabis through medical marijuana cards were at particularly high risk of developing CUD
- Cannabis may be effective against insomnia in the short-term, though further studies with objective sleep measures are needed
- Pain, anxiety, and depressive symptoms were the most common reasons people gave for wanting to use cannabis, but there was no substantial benefit of a medical marijuana card for any of those problems
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