Tens of thousands of children and young people in England are being given the hormone melatonin to help them sleep, prompting concern that the medicine is being handed out too readily with little evidence of its long-term effectiveness or safety.

Melatonin, which is produced naturally by the body in dark environments to help sleep preparations, has been authorised for use by people aged over 55. It has been hailed as a less addictive alternative to insomnia drug treatments.

Despite the fact it is not licensed for use by any other age group, 117,085 people under 18 were given melatonin “off label” – the term used for when a drug is given for an unapproved indication or in an unapproved age group – to aid sleep in the 2017-18 financial year. In the first four months of the current financial year, 69,280 prescriptions were given to under-18s.

The number of children and young people given the hormone has risen year on year, increasing by 25% from 92,511 prescriptions in 2015-16 to the most recent full-year figure. The data was obtained from the NHS business services authority after a freedom of information request.

The rise has largely been driven by an increase in the number of children over the age of seven given the drug. Use of the modified release form of the medicine, which releases the hormone more slowly than the liquid and tablet forms, increased by 42% from 2015-16 to 2017-18, rising from 62,384 prescriptions to 88,944 in three years.

But experts have expressed concern that the hormone may be being overprescribed by paediatricians due to the fact that there are few alternatives to support children with insomnia and other problems.

“These figures show we need more services for children who have sleep problems,” said Mandy Gurney, a health visitor and founder of the Millpond Sleep Clinic. “You can get very good results just looking down the behavioural and sleep hygiene line … The question is: do they need melatonin? But that piece of research has not been done.”

Gurney said she had been asked to train nursery nurses and health visitors in Wales, due to the high melatonin prescription rate. “The feedback after training was that the melatonin prescribing rate had come down.”

Dr Neil Stanley, an independent sleep expert and former director of sleep research at the University of Surrey, said he was surprised by the high numbers as there was very limited evidence of effectiveness in children other than in severely autistic children and blind children. He also noted that there was no data on its long-term safety.

“It’s a prescription of desperation really; doctors don’t know what to do about sleep and feel they have no alternatives,” Stanley said. “That is terrible as it affects all body clocks and it will affect children’s developmental clocks and we have no idea what that does.”

When given as a medicine, melatonin is usually made synthetically in a laboratory. The short-term side effects are thought to be minimal, but it can cause headaches, nausea, dizziness and drowsiness. However, in the long term there are ongoing concerns based on studies in animals showing melatonin can affect puberty-related hormones.

Dr Michael Farquhar, a consultant in sleep medicine at the Evelina children’s hospital, part of Guy’s and St Thomas’ NHS foundation trust, was more cautious, describing the prescription of melatonin as “not a good or bad thing”.

He said: “It can be right for the right child in the right context … I would expect to see increase in use but whether it is a valid increase in prescription is hard to say. We would need to know the reason it is being prescribed and whether there was a benefit in its use … A much bigger piece of work is needed to find that out.”

Farquhar said he was concerned that some people saw melatonin as a quick fix. “Behaviour interventions are more likely to be effective in the long-term and a better paediatric principle,” he said.

The National Institute for Health and Clinical Excellence (Nice) says melatonin appears relatively safe in the short and medium term (up to 18 months). However beyond this the picture is unclear.

“It’s important to put numbers into context. So 117,000 patients: that is still 1% of the child population, roughly speaking. It’s not a small number but if you think it’s perfectly valid to give the hormone for sleep difficulties among children with autism, ADHD and learning difficulties as a minimum, you’re pushing 5% of the population,” said Dr Max Davie from the Royal College of Paediatrics and Child Health.

“What is important about the data is that it suggests a great need for sleep services within children’s health services. It is not enough to only have a bit of advice and if that doesn’t work then offer melatonin,” he said.

Davie said the evidence of melatonin being prescribed inappropriately was mainly anecdotal and was hard to police. “On the one hand I wish it wasn’t the only thing we had to offer, but on the other hand there isn’t anything else, so what have you got to do?”

The figures are published as experts warn that young people’s lack of sleep is a hidden health crisis. Last month, the Guardian revealed that thousands of children and teenagers faced a mounting sleeplessness crisis, after the number of admissions to hospital of young people with sleep disorders rose sharply in six years.

Additional reporting by Matthew Hanrahan

• This article was amended on 6 November 2018 to make clear that the figures apply to England.