Antidepressant-like effects of insulin and IGF-1 are mediated by IGF-1 receptors in the brain.

Depression is associated with uncontrolled diabetes, which indicates a lack of insulin effect, yet the role of the insulin receptor in mediating depression is not clearly established because insulin receptors are not required for glucose entry into the brain. However, insulin receptors are important for brain function since insulin receptor knockout mice have depressive-like activity. Depression and cognitive problems are also associated with low insulin-like growth factor-1 (IGF-1) in the elderly.