There are different strains of marijuana. Some are more energizing, and some are calming and sedating depending on the balance of the different cannabinoids.
First, here’s a quick primer on the science behind marijuana. This herb works because it contains different cannabinoids, two of which you’ll see most often:
Cannabidiol (CBD). CBD has a number of health benefits, and is nonpsychoactive, meaning it doesn’t cause you to feel “high.”
Tetrahydrocannabinol (THC). THC, a psychoactive cannabinoid, is primarily responsible for that “high” feeling. Something else THC is responsible for? Inducing sleepTrusted Source. So you’ll want a strain that contains more THC than CBD.
According to a 2008 studyTrusted Source, ingesting marijuana strains with higher levels of THC typically reduces the amount of REM sleep you get. Reducing REM sleep means reducing dreams — and for those who experience PTSD, it could mean reducing nightmares.
So the theory is that if you spend less time dreaming, you’ll spend more time in a “deep sleep” state. The deep sleep state is thought to be the most restorative, restful part of the sleep cycle.
Still, REM is important for healthy cognitive and immune functioning, and marijuana with higher THC levels could impair your sleep quality if taken long term.
But this isn’t true across the board. Some studies have found that sleep can actually be impaired by regular use of marijuana. It’s clear that marijuana changes sleep cycles.