Insomnia patients in the UK who were prescribed cannabis-based medicines reported better sleep that largely persisted for a year and a half. The real-world analysis, published August 27 in PLOS Mental Health by researchers at Imperial College London, tracked 124 adults and found improvements in sleep, anxiety, and pain with few serious drawbacks.
The headline number is simple. Sleep quality scores more than doubled at one month, then settled to a still improved level by 18 months. Gains were biggest early, but they did not disappear. That arc, improvement followed by a gentle decline, is the shape you would expect if tolerance creeps in. And the authors hint that it might.
Block out the noise, then consider the stakes. Chronic insomnia drains productivity, worsens mood, and exacts a quiet economic tax on families and workplaces. Access to gold-standard therapy, cognitive behavioral therapy for insomnia, remains scarce. Many sleep drugs carry dependence risks or are simply hard to get. In that context, patients seeking “sleep that lasts” are shopping for alternatives. Medical cannabis is already on the shelf.
Early results in this cohort were strong. On the Single-Item Sleep Quality Scale, mean scores rose from 2.66 at baseline to 5.67 at one month, then 5.41 at three months and 3.81 at 18 months. Anxiety scores, measured by GAD-7, moved the right way too, with the largest change at one month and smaller, still significant, improvements thereafter. Patients also reported less pain and better quality of life on selected EQ-5D-5L dimensions. Only 11 of the 124 participants reported adverse events, mostly fatigue, transient insomnia, or dry mouth. None were disabling.
One caveat lands squarely in the “real-world evidence” bucket, and the researchers are upfront about it. The study is a case series, not a randomized controlled trial, and it relied on patient-reported outcomes without a placebo group. That invites expectancy effects. It also used a conservative data approach that may flatten later gains by carrying forward baseline values when follow-up data were missing. Still, the trend line is clear enough to be worth our attention.
“Over an 18-month period, our study showed that treatment for insomnia with cannabis-based medicinal products was associated with sustained improvements in subjective sleep quality and anxiety symptoms,” said Simon Erridge.
The registry offers some texture about how people actually dose. Median daily THC climbed from 20 mg at baseline to about 120 mg by 18 months, while CBD rose modestly. The most common regimen was dried flower. Older participants, those over 50, were more likely to hit a minimal clinically important improvement in sleep by 18 months. That detail is a buried lede with practical edges for clinicians.
But the tolerance question lingers. The magnitude of benefit tapered over time even as doses increased. The researchers note signs of possible tolerance, a reminder that individualized plans and regular reassessments matter when the goal is sleep that lasts. It is also worth noting that several authors are affiliated with Curaleaf Clinic, which operates the registry, a disclosure that belongs in any grown-up conversation about evidence and incentives.
“It was particularly interesting to observe signs of potential tolerance over time, which highlights the importance of continued monitoring and individualized treatment plans,” Erridge explained.
Where does this leave the average patient who has cycled through melatonin, Z-drugs, and long waits for CBT-I? Not with a cure, and not with a blanket recommendation. The study’s design cannot prove causation, and randomized trials have shown mixed results, especially with CBD-only formulations. Still, the real-world signal here is hard to ignore. For people who have tried the usual suspects and still lie awake at 3 a.m., medical cannabis might be a pragmatic option, with eyes open to trade-offs, follow-up, and cost.
The market angle is obvious. If future randomized trials firm up these gains, insurers and health systems will face a choice between covering supervised cannabis care or paying the ongoing bill for untreated insomnia. One costs money. The other costs productivity, safety, and quality of life.
Explainer: What This Study Actually Measured
This was a case series from the UK Medical Cannabis Registry that followed 124 adults with primary insomnia for up to 18 months after starting cannabis-based medical products. Researchers tracked patient-reported outcomes at 1, 3, 6, 12, and 18 months, including a one-question sleep quality score (SQS), an anxiety scale (GAD-7), and a quality-of-life index (EQ-5D-5L). There was no control group, so the study cannot prove cannabis caused the improvements. Missing follow-up responses were replaced with each person’s baseline score, which can dampen later improvements. THC doses generally increased over time, CBD rose modestly, and dried flower was the most common route. Adverse events were uncommon and mostly mild.
Journal: PLOS Mental Health
DOI: https://doi.org/10.1371/journal.pmen.0000390
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