Most would agree that mental stress contributes to physical illness. For example, if a person is under mental stress for any reason, it may interfere with their sleep, so they become chronically fatigued. It is a well known medical fact, as reported by the National Sleep Foundation, that adults need at least seven hours of sleep nightly to maintain proper health. If a person gets less than seven hours of sleep in a 24 hour period, this will definitely impact their health by not allowing their immune system to function properly to fight off illness. Not getting at least seven hours of sleep nightly will also impact their attitude, and this may also negatively impact their interactions with family, friends and co-workers.