On the outside, Andrea seemed like a devoted, involved stay-at-home mom. But inside, she was battling a mental disorder that disrupted her thoughts—and, she says, led her to do the unthinkable.

Andrea and her husband of 16 years already had a 13-year-old daughter when they decided to have a second child, a little boy they named Garrett. "He was precious," Andrea says. "He was so smart. He was already reading in kindergarten. He would entertain the class. He was so outgoing."

As Garrett grew older, Andrea was active in his school and volunteered for the PTA. But underneath the surface, she says she was troubled with dark, painful thoughts. "I struggled," she says. "Something didn't seem exactly right. I had bad feelings about myself that I was worthless, that I wasn't a good mom, that I wasn't a good person."