Predicting Health Problems
We all know that having a family history of an illness can put a child at risk. Some diseases, such as cystic fibrosis and hemophilia, are directly caused by an abnormality on just one gene. "Children who inherit a defect in the gene for cystic fibrosis from both parents, for example, will almost certainly get the disease," says Dr. Garber. However, most conditions involve multiple genes and complex traits that may increase a child's risk but not automatically doom him to developing the disease down the road. Type 2 diabetes is strongly genetic: If you have it before age 50, your child has a one-in-seven chance of developing it as well. However, people in non-Western countries who eat better don't get diabetes as often, which shows that lifestyle can reduce the risk. Similarly, genetics account for an estimated 75 to 80 percent of the difference between a skinny kid and an obese one, but even if a child has "fat genes," he can avoid weight-related problems like heart disease if he has healthy habits.
"Being aware of the risk can steer you and your child to healthier choices all her life," says Dr. Garber. For example, if your father had skin cancer and your child has strawberry-blond hair, you should be extra vigilant about using sunscreen. Parents with a history of depression can be on the lookout for symptoms in their kids and get them help as soon as possible -- if the condition ever occurs.
And that's a big if. "The more we know about the interplay of genetics and environment, the more we realize that human health and behavior are too complicated to be caused by just one thing," says Dr. Carey. "Our kids are like us in some ways but not in all. Whenever parents say, 'My child is just like me,' they usually qualify it by saying 'except for....'"