Under the national nutrivigilance scheme, reports of adverse effects likely to be associated with the consumption of food supplements containing melatonin have been brought to the attention of ANSES. A retrospective analysis of these reports, combined with the considerable level of consumption of this type of supplement, led ANSES to conduct an assessment of the potential health risks. In its Opinion of February 2018, the Agency highlighted the existence of populations and situations at risk, for which the consumption of melatonin in the form of a food supplement should be avoided or medical advice should be sought. This mainly concerns pregnant and breastfeeding women, children and adolescents, people suffering from inflammatory or autoimmune diseases, people with epilepsy, asthma, or suffering from mood, behaviour or personality disorders, as well as anyone being treated with medication. People carrying out any activity requiring sustained vigilance where drowsiness could pose a safety problem should also avoid its consumption.