|Title of host publication||The Wiley Encyclopedia of Health Psychology|
|Subtitle of host publication||Volume 4: Special Issues in Health Psychology|
|Editors||Lee M. Cohen, Suzy Bird Gulliver|
|Place of Publication||United States|
|Publisher||John Wiley & Sons|
|Number of pages||24|
|Publication status||Published - 2021|
Sleep impacts myriad aspects of physical and mental health, daytime function, and quality of life. While we have solid hypotheses regarding the specific functions of sleep, there is no simple answer to the question “Why do we sleep?” This may help explain why society has less regard for sufficient good‐quality sleep than other health behaviors, such as exercise, proper diet, and the need to stop smoking. Sleep is a highly complex behavior, arising from interactions between brainstem, midbrain, and cortex, neurotransmitter pathways, and hormones. It is this complexity that makes sleep so vulnerable to disruption. Sleep is vital to overall health, with links to many physical and mental health disorders. The aim of this chapter is to provide an overview of sleep and common strategies for measuring it, as well as to illustrate how sleep and health affect one another in a bidirectional manner using three examples.