Study: Common Sleep Drug May Leave Users Too Impaired To Drive The Next Morning

Taking Seroquel for Sleep? Study Suggests Avoid Driving In The Morning

Millions of prescriptions are written each year in the United States for quetiapine. A powerful psychiatric drug commonly known by the brand name Seroquel, quetiapine is now one of the most widely prescribed off-label sleep aids in the country. Now, a new clinical trial found that a low dose of the drug, originally approved to treat schizophrenia and bipolar disorder, helped people with sleep apnea sleep longer and spend less time awake during the night. Unfortunately, those same people showed dramatically slower reaction times and significantly worse driving simulator performance the next morning. Some of them had no idea.

In 2023, quetiapine was prescribed 10.7 million times in the United States, with 76% of those prescriptions written at doses below what the drug is officially approved for. An estimated 80% of people with sleep apnea are never diagnosed, meaning a significant number of quetiapine users may have undetected sleep apnea and no idea how the drug is truly affecting them.

Researchers at Flinders University in Adelaide, Australia, set out to fill that gap. Their study, published in the Annals of the American Thoracic Society, is the first to systematically examine what happens when people who have both sleep apnea and difficulty staying asleep take a low dose of quetiapine, looking not just at the night itself, but at how they function the next morning.

15 Sleep Apnea Patients Took Quetiapine, Then Got Behind the Wheel

Fifteen adults, seven women and eight men, were enrolled; all had confirmed sleep apnea and reported moderate to high difficulty staying asleep. Participants had an average age of 61 and moderate to severe insomnia symptoms. Each person completed two separate overnight sleep studies in a laboratory, roughly one week apart. On one night, they took 50mg of quetiapine just before lights out. On the other, they took a placebo. Neither the participants nor the researchers scoring the results knew which pill was which until all data had been collected, a design widely considered the gold standard for this kind of research.

Each night, participants were monitored for brain activity, breathing, oxygen levels, and leg movements across an eight-hour window. Within 30 minutes of waking, they completed a driving simulator task designed to replicate a monotonous nighttime drive on a rural road, followed by a 10-minute reaction time test.

The Night Looked Promising, But the Morning Did Not

On quetiapine nights, several sleep measures improved. Participants stopped breathing less often, dropping from an average of 27 episodes per hour to 20, and gaining more than 40 minutes of total sleep time. Wake time in the middle of the night fell by roughly 45%. Blood oxygen levels stayed stable throughout.

Morning performance told a different story. Reaction times were significantly slower after quetiapine than after placebo. Attention lapses (moments where reaction time exceeded half a second) more than tripled. Participants swerved far more from their lane in the driving simulator. Simulated crashes were more frequent on quetiapine nights, though the study was not large enough for that result to reach statistical significance on its own.

To put those driving numbers in context: participants in the placebo condition already showed steering impairment roughly double that of healthy drivers from earlier simulator studies. After quetiapine, that gap widened to nearly triple. These were people who had slept a full eight hours and were still performing worse than healthy drivers, and the drug made it worse.

When Quetiapine Users Don’t Know They’re Impaired

One of the more troubling findings had nothing to do with sleep data or the simulator. It had to do with self-awareness.

Most participants, 11 out of 15, felt sleepier the morning after quetiapine, which at least matched their actual performance. But two noticed no change in sleepiness, and two more felt more alert, even though their objective test results showed worse performance on both the reaction time and simulator tasks. As the researchers noted, roughly one in four people may not recognize, or may actively underestimate, how impaired they actually are after taking the drug.

A person who feels fine is far more likely to get behind the wheel, go to work, or operate machinery, completely unaware that a pill taken the night before has quietly dulled their reflexes.

Researchers Warn Quetiapine Users to Avoid Driving for at Least 9.5 Hours After Each Dose

About one in three participants experienced mild to moderate side effects on quetiapine nights, including nausea, restless legs, and a sudden blood pressure drop upon standing. All resolved within 48 hours, though two participants required a medical evaluation.

Researchers called for larger, longer-term studies before quetiapine can be considered appropriate for routine clinical use in people with both sleep apnea and insomnia. In the meantime, they recommended avoiding driving or other safety-critical tasks for at least 9.5 hours after taking quetiapine, and urged primary care providers to weigh that risk carefully before writing the prescription.

Sleeping longer is a genuine benefit. Arriving impaired at the wheel the next morning is a cost worth knowing before filling that prescription.

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Disclaimer: This study examined a single 50mg dose of quetiapine in 15 adults over one laboratory night and cannot establish long-term effects or real-world crash risk. Results may not apply to all doses or patient populations. Consult a qualified healthcare provider before making any changes to medication.

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