When assessing the progress of society, there has been a tendency to move from easily quantifiable features—such as economy, education, and general health—toward an emphasis on mental issues ^[1][2]. The idea was made famous by the fourth King of Bhutan when he, in 1972, declared that, in Bhutan, gross national happiness (GNH) is more important than gross national product. Today, it has become customary to include items probing happiness in surveys on how various nations are doing, as exemplified by the World Happiness Reports regularly published by the Sustainable Development Solutions Network (an initiative of the United Nations).

In order to aim for enhancing happiness, it is important to understand the nature of happiness. As our brains are a product of evolution, one heuristic approach is to consider the various functions, or modules, that evolution has incorporated into the human brain. Included in this list are modules responsible for positive and negative feelings. These modules can be construed as the features responsible for our capacity for happiness; that is, the effect these modules have on conscious experiences decides how good or how bad you feel. In other words, happiness is a question of the net output of the brain’s modules responsible for feelings. I shall present a model that suggests when these modules first evolved, what function they were meant to perform, and what is presently known about their neurobiology.

After presenting this evolutionary model of happiness, I shall briefly discuss the role of happiness as a target when attempting to improve society. Finally, I add some words as to why the level of happiness may not be optimal today and suggest a strategy aimed at enhancing mental health and happiness.

The term happiness as used here covers the mental part of the quality of life. Life satisfaction and subjective well-being are, in the present context, closely related terms. It should be pointed out that notions such as contentment and hedonic and eudemonic pleasure are covered by the present concept of happiness.

Mental health and happiness are correlated insofar as the more common mental disorders imply activation of negative feelings—as exemplified by anxiety (here understood as hyperactivity in the fear module) and depression (hyperactivity of the low mood function). The diagnosable disorders of anxiety and depression are presumably only the ‘tip of the iceberg’, in that many more suffer from disproportional, but subclinical, levels of fear or low mood. While it is possible to have mental issues without experiencing any reduction of happiness, as exemplified by people with Down syndrome ^[3], in most cases, the two are intertwined.