Leptin a potential link between obesity and depression

Obesity poses a serious threat to public health, acting as an epidemic that affects individuals of all ages, ethnicities, and sociocultural backgrounds. Besides, psychiatric disorders, especially depression, are also highly prevalent. Given the high impact of both types of conditions and their potential interrelation, they have become the focus of numerous research endeavors. In fact, the relationship between obesity and depression is often viewed as bidirectional. Leptin, a hormone released by adipose tissue that regulates energy balance and appetite, is closely linked to obesity. Recent research indicates that this hormone may also influence mood and behavior, which motivates the analysis of leptin's role in the shared pathophysiology between obesity and psychiatric disorders. The emerging relationship between obesity and neurodegeneration, attributed to the presence of chronic inflammation associated with this disease, prompts exploration of the potential role of leptin in this persistent inflammation, thus contributing to the neuroinflammatory state implicated in the genesis or evolution of depression. Therefore, in the present study, we aim to conduct a scoping review of the relationship between obesity and leptin with depression. According to the literature, there is an increase in leptin levels in depression, playing a pathophysiological role in the inflammation associated with the risk of depression in obesity. Nevertheless, further clinical studies are needed to fully understand the mechanisms and implications of leptin in the development of depression in obesity.