Happiness in life is as much attributable to having the right genetic mix as it is to external factors such as relationships, health and careers, says a new study.

In the study, the researchers found that happiness is partly determined by personality traits and that both personality and happiness are largely hereditary.

With the help of a framework which psychologists use to rate personalities, called the Five-Factor Model, the researchers found that people who do not excessively worry, and who are sociable and conscientious tend to be happier.

In the study, researchers used personality and happiness data on more than 900 twin pairs and identified evidence for common genes which result in certain personality traits and predispose people to happiness.

The findings suggest that all those people who have the right inherited personality mix have an 'affective reserve' of happiness which can come handy in stressful times.

Researchers say that although happiness has its roots in our genes, around 50 per cent of the differences between people in their life happiness is still down to external factors such as relationships, health and careers.

"Together with life and liberty, the pursuit of happiness is a core human desire. Although happiness is subject to a wide range of external influences we have found that there is a heritable component of happiness which can be entirely explained by genetic architecture of personality," said Dr Alexander Weiss, of the University of Edinburgh's School of Philosophy, Psychology and Language Sciences, and the study's lead author.

The scientists suggested that this type of personality mix can act as a buffer when bad things happen.