A recent article in the weekly International Magazine The Economist ("The U-bend of Life" - December 18, 2010, page 33) reports that happiness doesn't just make people happy - it also makes them healthier and more productive. Here follow their stated details.

1. John Weinman, professor of psychiatry at King's College London, monitored the stress levels of a group of volunteers and then inflicted small wounds on them.
   The wounds of the least stressed healed twice as fast as those of the most stressed.
   
   
2. Sheldon Cohen at the Carnegy Mellon University in Pittsburg, infected people with cold and flu viruses.
   He found that happier types were less likely to catch the virus, and showed fewer symptons of illness when they did.
   
   
3. Andrew Oswald, Eugenio Proto and Daniel Sgroi of the University of Warwick UK, cheered up a bunch of volunteers by showing them a funny film, then set them mental tests and compared their performance to groups that had seen a neutral film, or no film at all.   The ones who had seen the funny film performed 12% better.

The Norwegian biologist Bjørn Grinde, in his book Darwinian Happiness, takes the importance of Happinss even a step further.   Here is part of a synopsis of his book from the Wikipedia :

Bjørn Grinde argues that human emotions find their cause in evolution and offers ways by which we can use this for our advantage.
More specifically, mammals are equipped with a nerve system that enables them to distinguish not only between pleasant and unpleasant sensations, but positive and negative experiences in general.

While the biological term fitness refers to the capacity to create offspring, happiness (or quality of life) is, at least in a biological perspective, a question of the qualities of the experiences our nervous system offers us.
In order to improve these experiences there are two main principles to consider:

1. To utilize the rewarding sensations the brain is designed to offer in a way that gives optimal long-term benefits; and, similarly, to avoid punishing sensations.
   
   
2. To avoid stress and maladaptive ways of living in order to have a healthy mind with optimal potential for positive experiences.

Humans may actually have been equipped with more powerful positive and negative sensations, compared to other mammals, due to our capacity for free will. That is, evolution might tend to add stronger incentives for behavior benefiting the genes in an individual with a powerful free will; as otherwise, the free will could easily result in maladaptive behavior.

I find this a very exiting idea, as it strongly suggest that the pursuit of Happiness (as well as all other qualities we consider as good, positive or beautiful) actually helps to steer the evolution of our human species as a whole onto a progressive, positive course.

Therefore the pursuit of happiness produces benefits at three levels :