Complex sentence: Heavy cannabis use can lead to decreased levels of REM sleep and increased levels of slow-wave sleep along with reduced mental function the next morning; however, 5 mg doses of THC and CBD have been shown not to have these effects.
Split into simpler sentences: Heavy cannabis use can lead to decreased levels of REM sleep and increased levels of slow-wave sleep along with reduced mental function the next morning. However, 5 mg doses of THC and CBD have been shown not to have these effects.