In the yogic tradition, headstands, or Shirshasana, are a revered yoga position, and are said to have many health benefits such as: an increased blood flow to the brain, improved concentration and balance, stimulating the digestive system, and also endowing a calming effect onto the practitioner. 

All I know, is that I get a real urge to do headstands when I am laying in bed, or in a field of grass. There is something so satisfying and exhilarating about turning your body upside down, feet to the sky. Like an expression of joy that radiates upwards.