I feel the cannabinoid and terpene profiles determine these REM cycle disruptions and grogginess just the same as they affect the onset of being sleepy. I sleep great on indica based land races, but terrible on most modern strains that have a higher THC percentage or hybrids of sativa strains. Hopefully in the future we can break down these differences in the profiles of each strain rather than having blanket studies and opinions that might be neglecting that these profiles can be significantly different in their effects, especially regarding sleep and medical use.