Very interesting post to which I have several comments:

• There is a correlation of sun light exposure and uplifted mood - less depression when you spend time under (free) sunlight. Another reason for kids to play.
• Grownups could easily fall in the same category of unhappy at work and happy in weekends. They need play, too.
• Diet is often overlooked, but has an incredible impact on depression, energy, and ability to focus.
• Sugar, wheat and dairy, as well as processed foods are a mainstay of the American diet. And many countries are following suit. These foods cause addictive reactions in our body to crave more of the same. It isn't a matter of willpower to resist them, but automatic bodily functions for survival.
• If we get off that junk food merry-go-round for just a few days, we become much more aware of how much better we feel. Internal decision making, only now, can play a role: Do I want to eat this food which gives me temporary joy, or do I want to eat foods that support my thinking ability, physical capability, mood, and won't make me crave more foods that don't support me?