Stress activates the fight-or-flight response, which can cause permanent damage to stem cells in hair follicles that regenerate pigment. Stress leads to the premature depletion of the pigment reservoir.

Living less than 50 meters from a major road or less than 150 meters from a highway was linked to increased risk of dementia, Parkinson's, Alzheimer's, and MS, likely due to increased pollution.

Sun exposure regulates how fat cells produce energy; spending too much time indoors may disrupt this. Sunlight is required for normal energy metabolism, which could prevent metabolic syndrome.

Eating irregularly, especially on weekends ("eating jet lag") is linked to increased BMI. The highest increase was when meals were eaten 3.5-hours different on weekends versus weekdays.