Positivity, stubbornness and a conscientious work ethic could be key to living a longer life, a new study has found.

Researchers examined the mental and physical health levels of a group of Italians between the ages of 90 and 101 and found that there were many common psychological traits between them.

The study, which was published in International Psychogeriatrics concluded that the elderly participants had better overall mental well-being than their younger family members - they attributed this to their longevity.

Scientists at the University of California San Diego and the University of Rome La Sapienza surveyed 29 participants who lived in remote villages in southern Italy.

They assessed their mental and physical health through a series of tests and interviews.

For comparison purposes, they also conducted the same measures on the participants’ younger relatives who were asked to describe the personalities and lifestyles of their older family members.

In addition to having a sunny outlook on life, the researchers found that a lot of the elderly participants shared stubborn personality traits, which they claim can be psychologically beneficial because these people will tend to care less what others think of them.

Another common theme between the elderly participants was a passion for rural life.

"There have been a number of studies on very old adults, but they have mostly focused on genetics rather than their mental health or personalities," said Dilip V. Jeste, lead author of the study and professor of psychiatry and neurosciences at UC San Diego.

"The main themes that emerged from our study, and appear to be the unique features associated with better mental health of this rural population, were positivity, work ethic, stubbornness and a strong bond with family, religion and land,” he added.