(CNN) -

After Katherine Stone's first child, a son, was born 12 years ago, she immediately felt "super anxious."

Her son had jaundice, a relatively common yellow discoloration of a newborn's skin and eyes. "I thought he was going to die," said Stone, an Atlanta mom of two.

When hospital staff wanted to discharge her while her son remained behind for more treatment, she refused to depart, so she had to pay full price for a hospital room to stay.

"I was like, I'm not leaving ... I'll be a horrible mother if I walk out of this hospital, so I was already intently hyper-vigilant," Stone said in an interview.

Things only got worse when she arrived home. She constantly scrubbed bottles and kept reorganizing the basket of diapers so they were all straight.

Then, around seven weeks postpartum, Stone had the first of what are called intrusive thoughts -- frightening notions about what could happen to you or someone else in your life. She thought about smothering her son with a burp cloth.

She reached out for help about a month later, not because she thought she could get better if she got treatment; she just wanted the pain to go away.

"I'm not insane?"

"I thought they would cart me off either to jail or a mental institution," said Stone. "I really thought when I told the therapist that I met with for the first time about my intrusive thoughts that she was going to pick up the phone right then and dial 911. And she goes, 'Well those are intrusive thoughts, and this is what that is, and it's very common.'"

"I'm not insane?" Stone thought, with relief.

She was diagnosed with postpartum depression and anxiety and was treated through therapy and medication.

As many as one in seven women in the United States, or nearly 15 percent of new moms, is believed to suffer from some form of mental illness during or after pregnancy, according to the American College of Obstetricians and Gynecologists.

The spectrum of illnesses goes beyond depression, which people don't realize, said Stone. Moms could be suffering from a range of mood and anxiety disorders; in the most rare and serious cases, impacting only 0.2 percent of all moms, they suffer from psychosis, the disorder that often garners the painful national headlines.

Those cases include one of the most horrific in recent memory, when Texas mom Andrea Yates drowned her five children in a bathtub in 2001, and one of the more recent, when Miriam Carey was shot and killed after she led police on a high-speed chase in the nation's capital last year with her 1-year-old, who was unharmed, in the car.

In the vast majority of cases, women with perinatal mental illness won't ever physically harm themselves or their children.

The birth of a mission

As for Stone, it took many months before she felt like herself again.

When she returned to her corporate marketing job, she'd go into the bathroom and just sit in a stall, she said. She'd think, "I don't know what I'm doing. I don't know who I am. I don't know where I am. I don't know what's going on."

Even after she got better, she felt alone and somewhat angry. How could a fairly educated woman like herself not know anything about intrusive thoughts or how postpartum mental illness could include anxiety disorders?

She decided to write a blog post. It was July 2004.

"I thought, 'I'll write and hopefully someone will read it,'" she said.

Ten years later, Stone and her blog, Postpartum Progress, are considered one of the leading sources of information and support for moms suffering from some form of perinatal mental illness. The blog, which half a million women access annually, has also led to the creation of a nonprofit with the same name focused on raising awareness, pushing for more scientific research on causes and treatments and improving screening for the disease.

"People always think you have a master plan and honestly, even from the start with the first blog post, there was never a master plan," said Stone, whom I interviewed last year and again this year for this story. "The focus was always on what can be done to help other moms so they're not alone."

'Climb Out of the Darkness'

To help raise money for the nonprofit, last year one of Postpartum Progress' board members suggested holding an event on the longest day of the year, the first day of summer, to shine the most light on the issue. Four weeks later, the first annual "Climb Out of the Darkness" was held, with 177 people from around the world climbing mountains, hiking and walking along beaches to raise $40,000 from family, friends and other loved ones.