When it comes to choosing a strain of marijuana, you have two, main choices: indica or sativa. An indica produces a body high whereas sativas are associated with cerebral effects, sometimes described as a "mind high." If you're having trouble sleeping, go with an indica. That's the common logic, at least; and there's good reason to believe it's true.

But the way that marijuana affects sleep is more complex than it might seem. In part, that's because sleep is a complex process, with various stages and brain waves and health benefits to consider. Anecdotal evidence suggests that cannabis is the ultimate sleep aid, allowing users to drift off into a deep, uninterrupted slumber—but there's more to it than that, scientifically speaking.

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Nearly 40 years ago, a researcher who went by I Feinberg wrote in the journal Clinical Pharmacology Therapy that "the effect on sleep of THC [the main psychoactive component of marijuana] administration closely resembles those induced by lithium." This was well before cannabis research really took off, and it serves as one of the first research-backed examples of how marijuana use impacted your nightly rest cycle.

There is a distinct difference between the way that cannabis affects people who experience normal sleep and those with sleep disorders such as insomnia. For people who don't usually have trouble falling asleep, marijuana will still probably speed up the process, and it has also been shown to increase overall sleep. One study also determined that THC and CBD, a non-psychoactive component of cannabis, were associated with more time spent sleeping.

Be warned, however: Higher doses of THC before bed have also been known to produce a "hangover" effect. That is not to say that smoking too much pot will give you a throbbing headache or nausea the morning after a heavy session; it is not the same hangover attributed to overindulgence in alcohol but rather a feeling of sluggishness, a mental fog that gradually lifts throughout the early hours of the day.

"THC tended to be associated with some decrease in awakenings in the first half of the night," researchers at the University of New South Wales determined. "The most significant side effect, however, was a 'hangover' phenomenon, or continued 'high' the next day, with some residual of temporal disorganization. It increased in intensity and duration with increase in dosage."

Here's the thing, though: even though plenty of marijuana users report smoking before bed to expedite sleeping, the health benefits of marijuana (with respect to sleep) are very remarkable when applied to those with sleeping disorders such as sleep apnea, insomnia, and night terrors.

People with medical conditions that impact sleep stand to benefit the most from cannabis use, with dramatic reductions in sleep disturbance reported across a wide range of nighttime sufferers. They are less likely to report early awakenings after smoking pot and "appear to improve quality of sleep without impacting on total sleep time."

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"The association between the use and cessation of MJ and sleep disturbance is biologically plausible and we believe that there are neurobiological mechanisms to explain such a relationship," Dr. Karen Bolla, the lead author of a 2008 Sleep study, wrote. "Our group of MJ users confirmed this, as many of them reported on the SHQ that they use MJ to help them sleep. Interestingly, the MJ users report negligible use of alcohol, sleeping pills, or other medicines to induce sleep."

But there is a hitch: "A major problem in the treatment of MJ users is that up to 76 percent of those who abruptly stop using MJ report disturbed sleep (strange dreams, insomnia, poor sleep quality), possibly increasing the risk of relapse."

Although it appears that marijuana improves sleep, current research is limited. Researchers have also expressed interest in exploring the relationship between cannabis and dreaming; we are eagerly awaiting the results.