Gene scans for everyone? Not so fast. New research suggests that for the average person, decoding your own DNA may not turn out to be a really useful crystal ball for future health.

Today, scientists map entire genomes mostly for research, as they study which genetic mutations play a role in different diseases. Or they use it to try to diagnose mystery illnesses that plague families. It's different from getting a genetic test to see if you carry, say, a particular cancer-causing gene.

But as genome mapping gets faster and cheaper, scientists and consumers have wondered about possible broader use: Would finding all the glitches hidden in your DNA predict which diseases you'll face decades later?