The effects of ghrelin on sleep, appetite, and memory, and its possible role in depression: A review of the literature

Objectives. - Ghrelin is an orexigenic digestive hormone that plays a role in sleep and memory. Our work aims is to synthesize the effects of ghrelin on appetite, sleep and memory, and also to evidence its role in depressive disorders. Methods. - A systematic search was carried out on PubMed with no time boundaries. The following MeSH terms were used: ghrelin AND (appetite regulation OR obesity), (sleep wake disorders OR sleep) (memory OR cognition disorders) (depression OR depressive disorder OR mood disorder). Results. - Ghrelin triggers appetite and alters meal patterns by making them longer and richer. This can lead to pathologies, obesity and insulin-resistance. Ghrelin seems to have a favourable effect on sleep in human beings. It tends to make sleep more efficacious and better quality. Finally, it seems to have an effect on synaptic plasticity in the zones involved in memory and it has been shown to improve memory capacity in rodents. Regarding depression, the administration of ghrelin leads to an anti-depressive effect in animals and in humans. Conversely, post anti-depressant ghrelin titrations have generally shown a decrease in ghrelin levels. Resistant patients seem to retain high levels. Finally, the seriousness of depression could be related to ghrelin levels. Conclusion. - Ghrelin plays a probable part in depression, especially for particular endophenotypes. A better understanding of ghrelin in depression could potentially help to optimize future therapeutic treatments. (C) 2017 L'Encephale, Paris.