Happiness is something we all want. However, happiness varies greatly from person to person. A new study shows that how happy we are depends on a wide variety of factors. An assistant professor of psychology at the University of California led the study. It could help mental health professionals to provide better treatments for people who have depression and anxiety. The professor wrote: "We have to understand the sources of happiness to build effective interventions." Her study has been published in the journal "Nature Human Behaviour".

The professor suggested that happiness comes from external circumstances (like income and possessions) or internal feelings. She said there were three models of happiness. The first is "bottom-up". This is based on our overall satisfaction with factors like wealth, jobs and relationships. This is the one used for the World Happiness Report. The second is a "top-down" model. This suggests happiness comes from our attitudes towards life. People can control this through meditation or therapy. The final model is a bidirectional one, where bottom-up and top-down models interact.