Experts say when it comes to mental illness, prevention and early detection are key. That's why the Hope Network hosted the first annual One in Five Marathon Relay at Millenium Park Saturday, to raise awareness about mental illness.

Meg Derrer, the Executive Director of the Hope Network Foundation, explains why it's called the "One in Five": "This year, one in five adults will experience a mental illness-but with early intervention, we can reduce the devastating effects."

Teams of five completed a full marathon. The first four runners each ran a 5-mile loop, and the last represented the one in five by taking on a more challenging 6.2-mile route.

Organizers estimated about 500 people participated, including Lt. Gov. Brian Calley.