A 25 year study by Bruce Headey at the University of Melbourne and his team has looked at what generates happiness in people. Starting initially looking at around 300 people per year it ended up consididering 60,000 per year by the end of the expanding study.

The results showed that certain changes changes in lifestyle led to significant long-term changes in life happiness. The notable point was that the changes were long term. This flies in the face of an older theory which suggested that level of happiness was genetically determined and changes in happiness level were just transitory with fairly short term reversion to the genetically predetermined norm.

Of the influences determining a persons happiness, the greatest was their partners level of neuroticism as determined by set tests for that factor. Altruism, family values, and shared strong devotion to a religion also were important. A persons weight was another factor for long-term happiness, especially women who reported significantly less happiness when they were obese. This was not mirrored in men however though underweight men scored slightly lower than those with healthy weights.