How much hair loss people experience is usually determined by our genes. For instance, if your grandpa lost all of his hair at midlife, you could face a similar story. But now, doctors say we might have some control over hair loss. Researchers at University Hospitals Case Medical Center in Cleveland, Ohio studied 150 sets of twins at a twin festival in Twinsburg, Ohio. Dr. Bahman Guyuron took photos of the identical twins and asked them a long list of questions: did they smoke, have children, etc. "Twins are destined to have similar faces, similar amount of hair," says Dr. Guyuron. So if there's a big difference in how they look, like the amount of hair, Dr. Guyuron figures it has to do with a person's lifestyle. Divorce and spouse death were among the strongest predictors of hair loss in women. Heavy drinking was another factor. For men who want to keep their hairlines from receding, cut down on sun exposure by wearing a hat, get some exercise and put out the cigarette. "Avoid smoking, reduce alcohol consumption, reduce the stress as much as they can," says Dr. Guyuron. Overall, it seems that stress is the main factor for both men and women. So stay stress-less if you don't want to be hairless.