A man who finds his wife's salary is eclipsing his own may feel that earnings difference in the bedroom -- and not in a good way.
That's according to a new study that found that men who made less than their wives were more prone to require impotence drugs, compared to when the income gap was the other way around.
Admittedly, the difference wasn't much: Men who were out-earned by their wives were 10 percent more likely to take drugs for erectile dysfunction, said study co-author Lamar Pierce, an associate professor of strategy at Washington University in St. Louis.
However, even a relatively small difference in income between the spouses boosted the odds that a man might need pharmaceutical help in the bedroom.
"Men who make [even] $500 less a year than their wives are 10 percent more likely to take ED medications than men who make $500 more," he noted.
The study was published online recently in the Personality and Social Psychology Bulletin.
A shift in the marital "income gap" seemed to be key: According to Pierce, the findings did not apply to couples where the woman already made more than the man going into the marriage. "Men who knowingly married a female [primary] breadwinner appear to suffer no costs from being out-earned," Pierce and co-authors wrote in the study.
Nor did the findings apply to unmarried couples who were living together.
To Pierce, that suggests that ''marriage is an important social construct dictating his role [as primary breadwinner]."
The study was done in Denmark, which is viewed as a socially progressive country, Pierce said. He believes the findings would apply in the United States, and probably even be more robust among American couples.
In the past 20 years, the percent of American wives who make more than their husbands has risen from 4 percent to 22 percent, said Pierce, citing research by others.
The new study focused on two databases. One included demographic information, such as income and other details, for all Danish citizens. Another included all medical prescriptions for the population. Pierce looked at data from 1997 to 2006,and zeroed in on more than 569,000 couples, aged 25 to 49, where both partners worked full time.
Men were not the only ones affected psychologically by income differences within marriage. For example, Pierce found that wives who out-earned their husbands were themselves more likely to take medications for insomnia and anxiety. Out-earned husbands were also more likely to take anxiety and depression medications compared to situations where the male was the major breadwinner.
The research suggests a link between marital income disparities and impotence, but it cannot prove cause-and-effect, Pierce stressed. He did add that he factored out issues such as health problems, which might affect income, and the link still held.
He can't explain for sure why the out-earned men turn to impotence drugs. "We can't directly say this is [a result of] them being emasculated," but it may be, he said.
Another expert sees two possible explanations. One might be that ''it is threatening for men to be out-earned by their wives, and that threat is carried all the way into the bedroom, which leads him to be less able to perform well sexually," said Kathleen Vohs, a professor of marketing at the University of Minnesota Carlson School of Management. Her work focuses on the impact of income/money on human psychology.
"Another explanation," she said, "which is similar but not quite, is that the husband might use the ED medication as a way to guarantee that he is not emasculated in the bedroom."
Pierce said it's important not to suggest that the trend toward female breadwinners is socially harmful. Many men are perfectly fine with, and very proud of, a spouse who earns more, he said.
However, he said, it is important for couples to think about this before they marry, and to marry someone with whom each is comfortable with the other's potential earnings, now and in the future.
And Vohs had this advice for men out-earned by their spouse: "Try not to take the discrepancy in income as having anything to do with your manliness," she said. "Try to remember that your partner loves you for who you are and not for how much money you earn."