The lifestyle of the average person today is quite different than that of our ancestors. Those living before the 20th century did not have the luxury of many of the innovations we have today. People’s days were active and spent outdoors, hunting, farming, building, and traveling. Communities were small and tightly knit. Sleep was more regular and diets were quite different (no McDonald's on every corner or 80 varieties of cereal at the grocery store).
Today, many of us feel the pressure of our fast-paced and demanding lives. We may work long hours, run from activity to activity, and be faced with a constant barrage of news and requests made possible by technological innovations (when was the last time you weren’t on your cell phone or in front of your television or computer screen for an entire day?). As a result, our diets have become filled with processed convenience food, our sleep is often shortened and disturbed, and we spend more time sitting at desks or on couches than being active outdoors. Additionally, in a culture that values independence and success over social connections, we have become increasingly isolated, living farther from family and having smaller groups to look to for social support.
While our lifestyles have changed dramatically over the last few centuries, the evolution of our bodies has not kept up. Our bodies were designed to live the lifestyle our ancestors lived, with a balanced diet, as well as plenty of exercise, sunlight, sleep, and social support. Dr. Ilardi developed the TLC approach based on increasing evidence of the mismatch between our modern environment and the environment our bodies were designed to live in. The elements of TLC can serve to combat this mismatch, thus helping to protect against a medley of mental and physical illnesses, including depression." - http://psych.ku.edu/tlc/
The Depression Cure: The 6-Step Program to Beat Depression without Drugs