Is it coded into men’s DNA that they shed their male friends once they get married or enter into a long-term relationship with a woman? Why is it that the friendships they do form tend to be with the husbands of their wife’s friends, or the fathers of their children’s friends (“dad friends”), which tend to fade away over time?

The de-friending phenomenon, particularly among middle-aged men, has been receiving attention recently from psychologists, spurred by research into the long-term health costs of loneliness (social isolation has been shown to reduce longevity: in Australia, women live on average four years longer than men).

“Many men, whose identity is tied up with their job, are happy to let their wives be their social director,” says Greg Pankhurst, a clinical psychologist whose client base in western Sydney is mainly male. “This can become a problem if a marriage breaks down, or after retirement if a bloke’s social network has been limited to his work colleagues.”

When men are asked why they don’t have mates outside their wife’s social network, they usually plead lack of time or that they can’t be bothered. But can this really just be chalked up to emotional laziness? Could it be that some heterosexual men feel weirded out by pursuing friendships with other men, out of fear of it being perceived as gay?