Weighted blankets are exactly what they sound like: Basically, they’re comforters with tiny pellets or metal chains woven throughout, so that weight is distributed across the body when a person lies underneath them.

According to the experts, these blankets can be used "to treat a variety of ailments, including insomnia, post-traumatic stress disorder, obsessive-compulsive disorder, attention deficit hyperactivity disorder, as well as circumstantial stress and prolonged anxiety." Since then, weighted blankets have seen a big jump in popularity—and a quick glance at their online reviews shows that plenty of people really do rely on them to help with conditions like anxiety and insomnia.

Could a weighted blanket really be the answer to your sleep or anxiety problems? It might be worth a try, says Jeneane Solz, PhD, an instructor of psychology at Columbia University Medical Center—but there are a few things you should know before making a purchase.

First, says Solz, there aren’t a lot of studies to back up weighted-blanket claims. "Most of the research on these products has been on people with developmental disorders, like children with autism," she notes. "And from those studies, we’re finding that there aren’t significant differences in terms of objective measures like how quickly kids fall asleep and the total time they spend asleep." What those studies do show, however, is that participants who use weighted blankets "seem to like it better than a regular blanket," says Solz. "It can feel nice and luxurious—like a big hug—and that may be helpful for some people." A few small studies have looked at the effect weighted blankets have on anxiety and insomnia in adults.

A 2015 study in the Journal of Sleep Medicine & Disorders, for example, found that participants’ sleep time increased and nighttime movement decreased when they used weighted blankets compared with regular blankets. They also reported that it was easier to settle down to sleep with the weighted blanket, and that they felt more refreshed in the morning.

In 2006, a 32-person study in Occupational Therapy in Mental Health found that 63% of participants reported lower anxiety after using a weighted blanket (compared to lying down with no blanket at all), and 78% said they felt more relaxed with the blanket than without. That study also found that weighted-blanket use was safe for healthy adults, having no effect on vital signs like pulse and blood pressure.

Maybe material softness or breathability is important.

Weighted blankets shouldn’t be a substitute for proven therapies for anxiety or insomnia especially if you’re currently in treatment for a mental health condition, get the okay from your doctor or therapist before buying one.

"For some, like people with panic disorders or agoraphobia, the sensation of a weighted blanket could have a counter-effect and make anxiety even worse," says Solz.