In modern society, chronic insufficient sleep (defined as gaining less sleep than required) has become epidemic among adolescents worldwide and is as a serious health risk. Insufficient sleep is associated with higher risk of developing neuropsychiatric and behavioral disorders, such as anxiety and depression, that are the primary drivers of disability worldwide. In this research, I will study in mice how losing hours of sleep across adolescence affects, in the long-term, neuronal connections (or synapses) in brain regions important for the control of mood and emotions. Altered size, density or molecular composition of synapses are a consistent structural finding in multiple neuropsychopathologies and underlie impaired neural circuit performance and impaired behavior. By gaining insight into the underlying biological mechanisms linking chronic insufficient sleep to psychiatric disorders I aim to identify potential therapeutic targets to improve mental health.