Do you take it? If not, the chances are you’ll know someone who does. In an age of insomnia, melatonin has become a must-have sleep aid; as ubiquitous as yoga or herbal tea. In America, it is available over the counter and, according to The National Sleep Foundation charity, 27 per cent of adults take it. The use of melatonin has more than quintupled between 1999 and 2018. In the UK, where it is prescription only, melatonin use rose by nearly 900 per cent between 2008 and 2019, and many more of us – exact numbers are unknown – buy it unlicenced online.
‘People say it’s safe because it’s natural. Well, Vitamin A is natural. You eat too much and it will kill you’
Melatonin is a naturally occurring hormone produced by the brain’s pineal glands which regulates the circadian rhythm, or 24-hour body clock, which tells us when to wake and sleep. Secretion increases after the onset of darkness, peaking in the middle of the night. Most who take the hormone synthetically before bedtime swear it is cure for insomnia.
However, evidence it can help chronic sleeplessness is limited, and many experts are concerned by melatonin mania. ‘It is massively overhyped. The effects on sleep are very mild indeed,’ says sleep expert Dr Neil Stanley, who adds: ‘People say it’s safe because it’s natural. Well, Vitamin A is natural. You eat too much and it will kill you.’
Unlike prescription sleeping pills, which impact receptors in the brain to slow the nervous system, melatonin is a ‘chronobiotic’ that shifts the circadian rhythm and ‘signposts the brain towards sleep, rather than switching wakefulness off’ explains sleep expert Dr Sophie Bostock, who also believes ‘the evidence for melatonin as a sleep aid is weak’.
While studies have found that melatonin can decrease the effects of jet lag – ‘but it can only shift your clock by about two hours,’ says Dr Stanley – taking it to get a better night’s kip appears to have little more than a placebo effect. An analysis of 19 studies involving 1,683 people, published in the journal PlosOne in 2013, found melatonin reduced sleep latency – the time it takes to fall asleep – by just seven minutes, and increased overall sleep time by eight minutes. A clinical practice guideline published in 2017 by the American Academy of Sleep Medicine, meanwhile, suggests melatonin should not be used to treat chronic insomnia in adults at all.
To have any positive effect, users have to know exactly when their melatonin production peaks. Take it too early or too late and your circadian rhythm will be disrupted and you could just feel more tired. ‘Timing is absolutely crucial and there are probably about four people in the world who can tell you, as an individual, when to take melatonin because it’s down to your melatonin cycle which you can only measure from a spit test,’ explains Dr Stanley.
Then there‘s the fact that melatonin is unlicenced, meaning that, in America, its safety hasn’t been tested by the Food and Drug Administration. Indeed, says Dr Stanley, ‘it’s not recognised as a drug. If you buy melatonin in Walmart you have absolutely no idea what dose it is.’ A 2017 study of American melatonin samples in the Journal of Clinical Sleep Medicine found that the actual melatonin content ranged from 83 per cent less to 478 per cent more than the label stated – worrying, given overuse of melatonin can worsen insomnia and has been linked to vomiting and joint pain.
More alarming still, of the over two dozen supplement samples researchers studied, 26 per cent were found to contain the hormone serotonin, a potential hazard for people taking SSRI antidepressants, which increase serotonin levels in the brain. Those taking this adulterated melatonin are inadvertently putting themselves at risk of serotonin syndrome – where they have abnormally high levels of serotonin – which can result in muscle rigidity and seizures.
Yet American users are still less at risk than us Brits, believes Dr Stanley. ‘At least in America you’ve got a name on the packet – somebody you could perhaps sue. Buying it off the internet is absolutely crazy. You have no earthly clue what you’re buying.’ Melatonin is only licensed on the NHS for over 55s (because production is thought to decline with age), people with jet lag and children with long-term sleep problems. Dr Stanley fears UK doctors are prescribing melatonin increasingly liberally because they ‘think they don’t have any alternatives.’
Although complications from taking melatonin are rarely mentioned, the government advisory body The National Institute for Health and Care Excellence lists headaches, abdominal pain, hypertension and anxiety among myriad ‘adverse effects’ and recommends talking therapies over medication to help sleep. Because melatonin can reduce blood coagulation – or clotting – it puts people on blood thinning medication such as warfarin at risk of excessive bleeding, while frequent use of melatonin has been linked to dementia. And, says Dr Stanley: ‘It disrupts the body clock so can affect the menstrual cycle in women.’
The full impact of melatonin on reproductive hormones is still unknown, but research in the journal Brain Sciences published last November found it could delay the onset of puberty in mice. So it is particularly concerning that prescriptions of melatonin among children rose by 168 per cent between 2015 and 2022, with over 60,000 patients under 17 prescribed it in March 2022. Almost all those prescribed it by paediatricians have attention deficit hyperactivity disorder (ADHD) or autism spectrum disorder (ASD), which affect the circadian rhythm, and there is evidence that children who take it fall asleep faster and sleep longer.
‘But there is concern that the majority of studies in children have been short term,’ says Dr Bostock. ‘It seems therefore to be taking unnecessary risks to prescribe melatonin for sleep problems when behavioural interventions are likely to be more effective. I’m most worried by the fact that young children are learning from an early age to rely on an external substance to help them sleep.’
In any case, Dr Stanley says, melatonin production can be controlled naturally: ‘You just need to sleep in a dark bedroom and avoid bright lights before bed. It’s common sense. You don’t need to take some nonsense off the internet.’
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