Wives are fast catching up to and even passing their husband in the race to be a family’s main breadwinner, but success has a very dark side on a couple’s sex life: Men out-earned by their wives suffer from higher rates of erectile dysfunction and women are more likely to be wracked with anxiety and insomnia.

A huge new study from a Washington University professor and two colleagues from Denmark found that if a wife earns just 8 percent more than her husband, he has a much greater chance of needing Viagra or another ED drug. And the more the gap grows, the worse the husband’s condition can get.