On average, men's lives are less healthy — and shorter —than women's. This disparity exists in part because women take better care of themselves than men do. But studies have found that in many cases, a man and a woman with the same condition may respond differently. Yet medicine often uses a unisex approach, which can have dire results. Here are a few examples.

Cholesterol. Men with elevated cholesterol levels are more likely to suffer a deadly heart attack than women, said Erik Madssen of the Norwegian University of Science and Technology. For a dozen years, his team tracked more than 44,000 men and women with high cholesterol. One third as many women as men suffered fatal heart attacks. But when you consider that fewer men participated in the study than women, men died at four times the rate as women.

Melanoma. Twice as many men than women die of the disease. Some of the gap can be explained by the fact that men tend to get melanomas on the back. But Keiran Smalley, a researcher at the Moffitt Cancer Center & Research Institute, said the female hormone estrogen may have a protective effect against melanoma.

Depression. Half as many men as women have depression diagnosed. Professionals who screen for depression typically ask about feelings of guilt or worthlessness, sadness, trouble sleeping, and losing interest in activities. Men, however, tend to express their depression by getting angry, taking risks, becoming workaholics, and abusing alcohol and drugs. When clinicians include both sets of criteria, men are just as likely as women to have depression diagnosed.