A wide circle of friends is key to the well-being of middle-aged men and women, a new U.K. study says.

Researchers studied more than 6,500 British residents born in 1958. At age 42, the participants did a psychological test to measure their well-being, and they shared their marital status, job and the age they finished school.

When asked at age 45 how many friends they had, one in seven said they had no contact with relatives outside their immediate household and around one in 10 said they had no friends. Four out of 10 men and around one in three women said they had more than six friends they saw regularly.

When analyzed at age 50, researchers found "significantly lower levels of psychological well-being" among men and women with few friends, compared to those with 10 or more contacts, the study said.

The more schooling the participants completed, the more friends they had, the researchers said. Being in a relationship also boosted kinship.

Relationships with relatives is also important, but only for men. Researchers found a lack of contact with relatives had no emotional impact for women.

The study was published in the online Journal of Epidemiology and Community Health.