You're shopping for groceries. Out of the blue your heart starts to race, your knees feel week, you feel like you can't breathe, like you might be having a heart attack. You wonder if you're losing your mind -- but you're not. You're having a panic attack. 

About 1 in 4 people have had at least one panic attack during their lives, yet few like to admit it. Because panic manifests through physical symptoms that can mimic a heart attack, a lot of people feel shame when they go to the ER and find there's nothing wrong with them. In the absence of a test that defines panic, a lot of people worry they might be losing their mind.  

Also this hour: Panic ensued in Times Square in early August when a motorcycle backfired. Fear of being caught in the crossfire of gun shots has led to a collective panic of loud noises in public places.