Weighted Blankets: How They Work

Weighted blankets, sometimes referred to as gravity blankets, were once a tool of therapists and psychiatry clinics. Now, they have gone mainstream.

But whether there are any health benefits to using weighted blankets to ease anxiety and other issues remains a matter of debate, with some experts even cautioning these 25-pound blankets might pose a hazard to children.

Weighted blankets are harmless when they are used for teens or adults, said Teresa May-Benson, an occupational therapist with the nonprofit Spiral Foundation in Newton, Massachusetts. But it should be noted that two deaths have been linked to the misuse of weighted blankets: one of a 9-year-old boy with autism in Quebec who had been rolled up in a heavy blanket, and one of a 7-month-old baby.

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The blankets have a long history of use in a type of occupational therapy called sensory integration therapy. This treatment is sometimes used to help people with autism or other disorders to focus on sensory experiences, which experts say may boost these individuals' ability to regulate their emotions and behavior. Weighted blankets are one tool therapists use to provide "deep-touch pressure," May-Benson said.

"It's very much based in deep pressure helping to calm that arousal level in the system and to help with self-regulation," May-Benson told Live Science.

Dozens of companies now sell the blankets, typically for between $150 and $300. The blankets are touted as relaxation aids and anti-anxiety tools, sometimes a little too readily; Kickstarter recently asked the makers of the "Gravity Blanket" to tone down the language used to advertise this blanket on the site.

The makers' original wording had claimed that the Gravity Blanket could treat ailments including insomnia, obsessive-compulsive disorder and anxiety, Stat News reported. But Kickstarter, a crowdfunding site, prohibits users from touting their products as cures or treatments for medical conditions.   

The idea behind deep-pressure touch is that it stimulates the release of serotonin and dopamine, two neurotransmitters that tend to make people feel more relaxed. Some research suggests that slow and gentle touch can stimulate portions of the limbic system, the brain's network for processing emotion and fear. Many people with sensory-processing disorders are hypersensitive to touch, May-Benson said, and deep pressure can help desensitize and calm them. [25 Scientific Tips for Raising Happy Kids]

But it's a little less clear whether weighted blankets do much on their own, outside of therapy. The studies done so far on weighted blankets and other deep-pressure tools like weighted vests have been small, and have often lacked aspects that are included in rigorous studies, like a control group.

Of course, some people find a lot of pressure comfortable, but others can't imagine going to sleep under 20 lbs. of fabric with sewed-in beads. Scientific studies aren't likely to change anyone's mind about whether he or she personally enjoys snuggling with a weighted blanket. 

The research on weighted blankets

Four studies have focused on weighted blankets. In the earliest of those studies, published in 2008 in the journal Occupational Therapy in Mental Health, researchers asked 33 adults to rest under 30-lb. (13.6 kg) blankets for 5 minutes. They found that 33 percent showed a greater drop in skin conductance — a measure of arousal that is based on miniscule differences in the amount of sweat on the skin — with a weighted blanket than without. Nineteen participants said they felt more relaxed with the blanket, while eight said they felt equally relaxed either way, and three said they felt more anxious under the blanket.

However, that study showed only that weighted blankets were safe for people to use, not whether they are effective in improving people's health. The researchers noted that the results suggested that just laying down was enough to physiologically relax most participants enough that any additional benefit of the weighted blanket disappeared. [5 Wacky Things That Are Good for Your Health]

Perhaps, the researchers wrote, a high baseline level of anxiety is necessary to see a physiological change from using the blanket.

In another study, published in 2012 in the journal Australasian Psychiatry, researchers found that the use of weighted blankets in an inpatient mental psychiatric unit decreased the amount of distress the patients reported feeling, and how anxious they felt toward their health care providers. But the blankets didn't seem to improve objective measurements like aggression or the hospital's need to seclude the patients away from others, the study said.

In a third study, published in 2014 in the journal Pediatrics, researchers tested using weighted blankets to help kids with autism who had problems sleeping. The study included a "placebo" blanket, containing light plastic beads to mimic the texture of the weighted blankets, which were filled with steel beads. The researchers measured how long it took the kids in the study to fall asleep, how often they woke during the night and how long they slept in total, using both reports by parents and activity monitors that the children wore.   

"We found nothing," said Dr. Paul Gringras, the head of the Children's Sleep Medicine Unit at the Evelina London Children's Hospital, who led the study. "We found no difference. It was kind of disappointing."

Children with autism are especially prone to sleep problems, Gringras said. So if weighted blankets helped anyone, he would have expected them to help his study participants, he said.

In the fourth study, published in 2016 in the Journal of the Formosan Medical Association, researchers suggested that the blankets may help people in stressful circumstances. The researchers found that the study participants who wore a weighted blanket during wisdom tooth extraction showed enhanced activity in the branch of the nervous system that takes over in times of low stress.

The results suggest that "deep-pressure input may be an appropriate therapeutic modality" for people in stressful conditions, the researchers concluded. [5 Surprising Facts About Pain]

Still, further studies are needed to look at how this effect may work, the researchers said.

Other types of deep pressure in kids

Other studies have looked at the effects of other types of deep pressure, besides weighted blankets, on children. One of the hallmark studies often used to tout weighted blankets was done in 1999, and led by animal science professor Temple Grandin, who has autism herself. In the study, published in the American Journal of Occupational Therapy, the researchers tested out a "hug machine" in 12 children who had autism. A person using the machine can pull a lever to bring pads toward his or her body, providing deep-pressure stimulation.

Five of the kids used the hug machine, and seven rested in the machine but didn't use it.

The researchers found a reduction in the amount of tension that the children who used the machine said they felt compared with those who didn't use the machine. The investigators did not, however, find changes in the kids' skin conductance.

In digging into their physiological data, the researchers found that those kids with higher arousal levels before the experiment were more likely to see their arousal levels drop due to the machine than those with lower baseline arousal.

A 2011 study in the American Journal of Occupational Therapy found that elementary school kids who had difficulty paying attention in class (but did not have an attention disorder) showed no benefits from wearing a weighted vest. Other studies have also found no effect.

However, in one 2014 study, researchers randomly assigned kids with ADHD to wear a weighted vest or not; they found that the vests were linked with improvements in attention and on-task behaviors and decreases in fidgeting.

Much of the available research on kids is done within classrooms, on small groups of kids who attend one school where a particular therapist, who is conducting the study, practices. The studies usually lack long-term follow-ups, and sometimes control groups. [7 Bizarre Drug Side Effects]

Deep pressure in adults

Studies on other types of deep pressure in neurotypical adults (who are not on the autism spectrum and without mental illness) are fairly rare, but those that have been done have returned ambivalent results. For example, a 1987 study using an air mattress that wrapped around and squeezed the body found no statistically significant changes in self-reported anxiety or in physiology among 23 healthy college students.

In 1992, Grandin reported research on the use of her "hug machine" in an experiment with 40 neurotypical college students. She found that 60 percent said using the machine was relaxing, while 40 percent said it wasn't. Two students became claustrophobic and had to get out of the machine.

A personal decision

In therapy, deep pressure is generally seen as a calming tool, but there are lots of different ways to deliver that pressure, May-Benson said. The therapist may provide a massage, have a child crawl under a large foam crash pad or use therapeutic brushes on the skin.

"Everyone's different," May-Benson said.

Grandin, for example, found this sort of touch so helpful that she invented her hug machine to provide it. And in one tiny study of four kids with ADHD, published in 2001, three out of the four children tested actually asked to wear the vest outside of the study time because it made them feel good.

Even if some of the effect is a placebo effect — and up to 40 percent of the effect of treatments on internalizing disorders like anxiety can be attributed to placebo effects, Gringras said — the experience of feeling better is real.

So what's the bottom line on weighted blankets? Proceed with caution for kids, May-Benson warned. Weighted blankets shouldn't be used on kids younger than about 7 or 8, she said, unless a therapist recommends one. [9 Weird Ways Kids Can Get Hurt]

For adolescents and adults, weighed blankets are unlikely to do any harm — but maybe try burrowing under your pre-existing stash of quilts and duvets to see how you feel before you lay out all that cash. And remember that there is a very well-tested, well-proven therapy out there for insomnia, Gringras said. It's called cognitive behavioral therapy for insomnia, and it's gotten the stamp of approval from the National Institutes of Health.

Original article on Live Science.