What melatonin is
ADHD and melatonin often come up together when bedtime turns into a nightly battle. Melatonin is a hormone made by the pineal gland in your brain. Your body starts producing it just after it gets dark, it peaks in the early hours and it drops off in daylight, which helps set when you feel sleepy. The tablet version adds to your own supply, and the NHS says it takes around one to two hours to work.
The ADHD sleep link
Lying awake at midnight with your head still going is a familiar scene for a lot of people with ADHD. A Dutch team led by Emma van Andel describes a delayed body clock, known as delayed sleep phase, as the most common sleep problem in adults with ADHD. In their trial of adults with ADHD and a delayed body clock, 77% had their natural melatonin rise after 9pm. The NHS also lists trouble sleeping as a side effect of methylphenidate.
Prescription-only in the UK
If you've seen melatonin gummies on holiday or on American websites, the rules here are different. The NHS says melatonin supplements aren't authorised for sale in the UK, it's a prescription-only medicine and ordering it online isn't recommended. It's mainly used for short-term sleep problems in people aged 55 and over, but the NHS names ADHD as one of the conditions where a specialist may prescribe it longer term, and for children when other ways of improving sleep haven't worked.
The children's trial
The best-known study is a 2007 trial by van der Heijden and colleagues in the Journal of the American Academy of Child and Adolescent Psychiatry. It included 105 children aged 6 to 12 with ADHD and long-running trouble falling asleep, none taking ADHD medication. Over four weeks, children given 3mg or 6mg of melatonin fell asleep about 27 minutes earlier, while the dummy pill group drifted about 10 minutes later. Melatonin also added around 20 minutes of total sleep.
Research in adults
Adult research is thinner. In van Andel's trial, published in Chronobiology International, 51 adults aged 18 to 55 with ADHD and a delayed body clock got sleep advice plus three weeks of either a dummy pill, a low 0.5mg dose of melatonin, or melatonin with morning bright light. Melatonin alone moved their body clock about an hour and a half earlier and cut self-reported ADHD symptoms by 14%, but both were back to where they started two weeks after stopping.
What it doesn't do
Melatonin isn't an ADHD treatment, and the studies are fairly clear about that. The children's trial found no effect on behaviour, concentration tests or quality of life, and NICE noted it couldn't make recommendations from it on those outcomes. A follow-up of the adult trial found that even though people's body clocks shifted, their actual sleep times didn't move with them, so the researchers said much more help with sleep habits was needed alongside it.
Side effects and interactions
The NHS says most people don't get side effects, but some get a headache or feel tired, sick or irritable the next day. If it leaves you sleepy in the daytime, you shouldn't drive. Lots of medicines can change how drowsy it makes you, including some antidepressants, sleeping tablets, warfarin and painkillers like ibuprofen. Alcohol and smoking can stop it working as well as it should, and herbal remedies that make you sleepy shouldn't be taken alongside it.
In everyday life
If sleep is a constant fight, the useful step is raising it with your GP or ADHD prescriber rather than ordering something online. Go in with a week of notes showing when you went to bed, roughly when you fell asleep, when you woke up and what time you took any ADHD medication. That gives them something concrete to work with. Don't change the timing or dose of prescribed medication to sort your sleep out without speaking to them first.
This information is for general education and is not personalised medical advice. Treatment and prescribing decisions belong to qualified healthcare professionals.