hether smoked or drunk or ingested in a fruity little treat or a brownie, marijuana has plenty of proponents, from college students to grandpas, busy professionals to laid-back stoners. Many of them swear by Mary Jane’s ability to remedy any number of ailments, not to mention its positive effect on creativity. But the evidence for cannabis as a sleep aid, while encouraging, is mixed.

Cannabis comes in two main varieties relevant to medicine: The psychoactive ingredient in marijuana, tetrahydrocannabinol or THC; and the non-psychotropic cannabidiol (CBD). Both show promise for relieving symptoms of pain, depression and various other conditions, and perhaps to promote sleep. The research is thin, however, in part because study efforts are limited by laws that thwart clinical trials. Also, there’s a lack of funding by drug companies that would rather invest in more lucrative, patentable treatments instead of a drug that’s already sold over the counter in many states.

Anecdotes abound, and I’d love to hear what you’ve found to work for you. But meantime, let’s see what science actually says about both types of cannabis and their ability to promote better sleep.

Packaged into everything from gummies to topical oils, CBD doesn’t get you high. But preliminary research does suggest it can alter brain activity, though much remains to be explored about how it works and what its effects are.

There are hints CBD may serve as a sleep aid, perhaps primarily by reducing anxiety and promoting relaxation. Its true effectiveness has not been well studied in clinical settings, however, and its long-term safety is not known, said Deirdre Conroy, PhD, clinical director of the Behavioral Sleep Medicine Clinic at Michigan Medicine. Studies that do suggest it can be helpful are small, and dosages vary to the extent of not pointing to helpful conclusions.

Some research even suggests CBD helps people stay alert. Which, you know, isn’t exactly great for sleep.