Evidence to support the use of melatonin to reduce the duration or severity of jet lag remains “inconclusive and conflicting” despite decades on the market, according to a new review.

Writing in the BMJ’s Drug and Therapeutics Bulletin, UK researchers suggest that doctors should avoid prescribing the hormone to patients suffering from jet lag, which they say is a short-term, self-limiting ailment.

In addition, melatonin can cause drowsiness, decrease alertness and may increase seizure frequency in those with epilepsy. It is not recommended for people with autoimmune diseases, severe renal impairment or severe hepatic impairment.

Their findings represent an update to a 1998 review that raised concerns about the lack of a product licence for melatonin formulations to ensure quality and safety.