A mental disorder leads people to believe their loved ones were replaced by an impostor!

Imagine that your parents had been abducted by aliens. They looked like themselves, but they weren't you're real parents, and there was no way to prove they were impostors.

Pretty scary, right? Unfortunately, some people suffer from a neurological disorder that makes them believe something very similar.

Those with Capgras Syndrome believe that their friend, spouse, parents or other close family member has been replaced by an identical impostor.

This syndrome usually occurs in those with paranoid schizophrenia, a brain injury or dementia. And it occurs more frequently in females.

Scientists believe that humans both consciously and subconsciously recognize faces. They believe that those with Capgras Syndrome can recognize faces but the emotional response connected to those faces does not come through.

This causes them to think the familiar faces they see aren't actually the people they are emotionally connected to.

(Source)