What the trial found
The strongest piece of evidence is a randomised crossover trial published in Pediatrics, run between 2010 and 2013 across Evelina London Children's Hospital, Oxford Brookes, York and the John Radcliffe.
Seventy-three children were randomised and sixty-seven analysed, aged from five to nearly seventeen, all with a confirmed autism diagnosis and severe sleep problems that had not responded to the usual community interventions — in other words, precisely the children for whom weighted blankets are recommended most often. Each child used a weighted blanket for two weeks and an identical-looking blanket of ordinary weight for two weeks, with sleep measured by a wrist actigraph rather than by impression.
The results were flat. No increase in total sleep time, which was the primary outcome. No significant difference in how long children took to fall asleep. No reduction in night waking. Nothing in sleep efficiency, behaviour or family functioning, and nothing in the parents' own sleep diaries either. The lead researcher put it plainly: no evidence that they make any difference to these children's sleep compared with normal weight blankets.
And yet both the children and the parents preferred the weighted blanket. That is the finding worth holding on to, because it is the one that gets left out of both the marketing and the debunking. The blankets were well tolerated, and the people using them liked them. They simply did not do the thing they are sold to do.
Which makes the honest position neither "they work" nor "don't bother". A child who finds a weighted blanket calming is not imagining it, and that is a reasonable thing to provide — within the limits below. What it will not do is fix a sleep problem, and buying one in the expectation that it will is how families end up disappointed and out of pocket.
Not overnight
This is the instruction most at odds with how weighted blankets are sold, and it is the consistent position of NHS therapy services following Royal College of Occupational Therapists guidance.
- Prolonged use is not recommended. The suggested maximum is twenty to thirty minutes.
- Use starts brief and lengthens only if needed, under supervision.
- Where one is used to settle a child, it comes off once they are asleep rather than staying on all night.
- The child is supervised while under it.
Some NHS services go further and do not recommend weighted blankets at all, on the grounds that the evidence does not support them.
The weight
The rule is no more than ten per cent of the child's body weight, and the guidance is to go as light as will still be effective rather than treating ten per cent as a target. Worked through:
- A 25 kg child — up to 2.5 kg
- 30 kg — up to 3 kg
- 36 kg — up to 3.6 kg
- 45 kg — up to 4.5 kg
- 60 kg — up to 6 kg
The manufacturer's own weight and size guidance applies on top of that, and a blanket sized for an adult does not become suitable for a child by being folded.
The rules that matter
These are not refinements. Each of them addresses a specific way the blankets have caused harm.
- The child must be able to get out from under it on their own. If they cannot, a weighted blanket is not appropriate for them at all.
- Head, face and neck stay uncovered.
- It is laid loosely over the child, never wrapped or rolled around them.
- It must not hang over the side of the bed, where the overhang adds drag and can pull it off or pull the child with it.
- Never as a restraint, and never to make a child stay put.
- Not combined with other weighted products — not a weighted blanket and a weighted lap pad or vest together.
- It has to fit the child, not the bed.
When one should not be used
NHS guidance lists conditions under which a weighted blanket may be unsafe:
- Breathing problems of any kind
- Heart problems
- Epilepsy
- Low muscle tone
- Circulation problems
- Skin conditions and certain allergies
- Difficulty regulating body temperature
- Any inability to remove the blanket independently
Services are also directed to weigh a few other circumstances before recommending one — among them an eating disorder, risk of self-harm, and anything that reduces alertness, including medication side effects and acute illness. Those are reasons to take advice rather than to buy one off a website.
Stop straight away if
- Breathing becomes difficult or laboured
- The child feels sick
- Temperature rises, or the child says they are too hot
- There is any sign of discomfort, distress or anxiety
And it is worth saying out loud to a child who has one: it can come off whenever they want, for any reason, including simply not liking it tonight.
Never for a baby
Weighted blankets, weighted sleeping bags and weighted swaddles are not recommended for any baby under one year, on two grounds: overheating, and the risk of the covering reaching the head.
This category has grown quickly — weighted sleep sacks and swaddles marketed for settling newborns — and the safer sleep position on all of it is the same. A baby under a year sleeps with no duvet, no quilt, no pillow and nothing weighted, in a room at 16 to 20°C. The rest of that is under safer sleep for babies.
Where the rules came from
The guidance is specific in the way it is because of a death. In Canada in 2008 a nine-year-old child with additional needs suffocated after being rolled inside a weighted blanket by a teacher. NHS guidelines on safe use cite that case directly as their basis.
It explains the shape of the rules above — laid over rather than wrapped around, never used as a restraint, always removable by the child, always supervised. The failure was not the weight. It was the wrapping and the inability to get out.
So, for a parent weighing one up
A weighted blanket is a reasonable thing to try for a child who finds deep pressure calming, used for twenty minutes or so in the evening, at the right weight, supervised, and taken off before or shortly after they fall asleep. Plenty of children like them, and the trial evidence says that preference is real even though the sleep benefit is not.
It is not a treatment for a sleep problem, and it does not belong on a bed all night. Where a child's sleep is the actual problem, an occupational therapist or the GP is a better first call than a purchase — and what does have evidence behind it is under children's sleep.