The project is designed to document in college undergraduates the relationships among sleep/wake timing and duration, use of mobile phones and other electronic devices, food timing and content, self-reported mood and physiological measures.

College undergraduates are studied in cohorts of ~ 50 in fall or spring semesters. They complete diaries once in the morning and once in the evening about sleep/wake timing, timing of social and school activities, and mood. They wear physiological sensors. They install (1) an application on their mobile phone that tracks timing, duration and de-identified sender/recipient of phone calls and text messages, use of internet or apps (but not the content or names of those internet sites and apps) and (2) meal content and timing. They also spend at least one overnight session providing saliva samples for later assay for hormones.

Inclusion Criteria:

• undergraduate at institution at which we have permission to perform study
• owning a mobile device on which the phone app can be installed
• ability to wear the wrist-worn sensors

Exclusion Criteria:

• no travel outside one time zone starting approximately 2 weeks before monitoring begins through end of approximately one month of monitoring.
• participation in a prior group studied

College undergraduates