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A new study published in the journal Psychopharmacology found that taking cannabidiol (CBD) nightly for two weeks did not impair thinking, memory, or reaction time in people with insomnia. Participants who took CBD reported feeling calmer, clearer-headed, and more coordinated the following morning compared to those who took a placebo. However, their performance on computerized tests of cognitive functioning remained unchanged.
Cannabidiol, often known as CBD, is a compound derived from cannabis that has gained popularity for its potential therapeutic benefits, including reducing anxiety and improving sleep. Unlike tetrahydrocannabinol (THC), another compound found in cannabis, CBD is not intoxicating.
In recent years, CBD has been widely marketed as a natural sleep aid, especially in regions like Australia where it is available over the counter. Despite its growing use, there is limited research on whether CBD affects how people think and function during the day, particularly for those with sleep difficulties.
“Cannabis has been used medicinally for centuries for the treatment of numerous conditions. There have also been a lot of anecdotal claims about the sleep- and mood-enhancing effects of CBD and other cannabinoids,” said study author Andrea J. Narayan, a PhD candidate at Swinburne University of Technology.
“At the time of the study, Australia had legalized the sale of a maximum dose of 150 mg CBD in pharmacies without a prescription. Very few studies have specifically looked at the direct effects on sleep and any potential indirect effects of this specific dose following its night-time consumption, so this topic was important to study—and personally quite exciting.”
The researchers conducted a randomized controlled trial involving 30 adults with moderate to severe insomnia symptoms. Participants were randomly assigned to receive either 150 milligrams of CBD or a placebo every night for two weeks. Before the two-week trial began, all participants completed a one-week placebo run-in period to identify those who might respond to placebo alone. Anyone who showed marked improvement in sleep during this week was excluded from the study.
The trial was designed to minimize bias. Participants, researchers, and staff were unaware of who received CBD or placebo, and both treatments looked and smelled the same. Each night, participants took their assigned oil dose under the tongue about an hour before going to bed. They also wore wrist devices to monitor sleep and kept daily logs of their mood and any side effects.
Cognitive functioning was tested using a computerized system called CogPro. These tests assessed attention, memory, reasoning, and reaction time. Participants completed these tasks at the beginning of the study, after one week of dosing, and again at the end of the two-week period. The cognitive tests were scheduled in the morning, more than eight hours after the previous night’s dose, to simulate the typical time people might go about their daily activities.
The study found no significant differences in cognitive performance between the CBD and placebo groups. Across a wide range of tests—including memory recall, working memory, and attention—both groups performed similarly. The only change observed was a small improvement in simple reaction time across the whole sample, which may have been due to participants becoming more familiar with the tasks rather than a treatment effect.
While cognitive performance did not improve, participants in the CBD group reported more favorable mood states compared to those on placebo. They consistently rated themselves as feeling calmer, more clear-headed, better coordinated, and more alert across the two-week period.
These effects were statistically significant and sustained throughout the trial. Those in the CBD group also reported feeling slightly more energetic and happier than those taking the placebo. Notably, these mood changes did not coincide with increases in drowsiness, lethargy, or sadness, suggesting that CBD had a mildly positive effect on morning well-being.
“People taking CBD reported feeling more calm, clear-headed, and coordinated in the mornings than those who took placebo,” Narayan told PsyPost. “We explored sleep in the same population and did not see any notable changes to night-time sleep. This could mean that CBD may improve some subjective states, which could suggest it has other secondary mood effects at these doses when taken for sleep.”
As for side effects, dry mouth was the most commonly reported issue among those who took CBD, although it was generally mild. Other side effects like nausea, dizziness, and light-headedness were rare and not significantly different from those in the placebo group. Only a small number of participants withdrew due to discomfort, and these symptoms resolved quickly.
The researchers emphasized that although the study did not find measurable changes in cognitive function, it also did not detect any impairing effects of CBD on thinking or attention. This contrasts with many common sleep medications, such as benzodiazepines, which are known to cause daytime grogginess, memory problems, and reduced concentration.
“There weren’t any noted positive or negative changes to daytime neurocognitive performance, but we still aren’t sure how this will relate to daily, real-life tasks such as driving, considering neurocognitive performance was measured using computerized tasks in our lab,” Narayan noted.
The researchers cautioned against drawing firm conclusions from this study alone. The trial included a relatively small number of participants and focused on a short, two-week dosing period. The 150-milligram dose used in this study is within the range available over the counter in some countries, but may not be high enough to fully assess CBD’s potential therapeutic effects.
“Though the results seem promising, we had a very small sample with a specific clinical condition,” Narayan explained. “We also explored the effects of only one dose of a cannabis isolate for a short period of time. This means that we can’t confirm these results to be true for other clinical populations, or for different doses of CBD, or other cannabinoid treatments.
“Until more studies explore and observe similar outcomes for daytime neurocognitive performance, it is also difficult to confirm that there are no hazards or strong benefits of CBD from this study alone.”
Overall, this study suggests that taking 150 milligrams of CBD each night for two weeks may help people with insomnia feel calmer and more clear-headed in the morning without impairing their ability to think or remember. While these results are encouraging, especially compared to more sedating sleep medications, more research is needed.
“In terms of road safety, the Drugs and Driving Research Unit at Swinburne University of Technology is already conducting a world-first study looking into the effects of medical cannabis on driving performance in patients with medical cannabis prescriptions,” Narayan said. “This is an incredibly important study for the safety of patients and overall road users in general.”
“In terms of the efficacy of medicinal cannabis, deeper exploration into the effects of different doses and ratios of cannabinoids on mood and sleep in different clinical populations is incredibly necessary.”
“I am particularly curious about the possibility of using current cannabinoid isolates such as CBD together with other known treatments to safely enhance therapeutic benefits in the treatment of mood and sleep conditions,” Narayan added.
