People thought they slept well; wrist monitors disagreed

A Northwestern Medicine study compared cannabis histories in 1,266 adults with a week of sleep measurements in middle age. Both recent and cumulative use were associated with lower objective sleep efficiency, more fragmentation and more time awake at night, while participants generally did not report worse sleep. The observational study cannot show that cannabis caused the difference, but it exposes an uncomfortable gap between feeling rested and the data on the wrist.