One in five. That's how many Canadians will have mental health issues at some time in their lives.

Despite its prevalence, mental illness still carries a huge stigma, and that could be costing sufferers their lives, a Toronto-area mother worries.

Lynda Thorogood's daughter, Stacey, 42, struggled for 20 years with mental illness before committing suicide last May.

For years, her parents thought she was simply a troubled young woman. It wasn't until Stacey's suicide attempts began two years before she died that her parents learned that their daughter was actually mentally ill.

"In her purse, she had written down that they'd diagnosed her with borderline personality disorder. That's the way I knew. That's the only way I knew," Lynda told CTV Toronto's Janice Golding in an interview this week.

Looking back now, Lynda says the signs were there for years, but her family didn't recognize them.

Stacey, who had been a valedictorian, dropped out of university and floated from job to job. She would lash out at her family, falsely accusing them of abuse. She had boyfriend after boyfriend and often accused them of abuse too.

"She would sometimes just phone up any family member and rage and say, ‘You're not my mother,' ‘You're not my sister,'" Lynda remembers.

"It never went through my head: mental illness. She was beautiful, she was intelligent. I thought she was lazy -- I had no clue."

Once Stacey's suicide attempts began, her family tried to help her, but didn't know how.

"It's just hell on wheels because… you're trying so hard to help this person you love so much and you can't help them," her mother says.

Her family knew she needed professional help. But Stacey refused treatment, and she slipped through the cracks.

"Each time she was in the hospital, I thought ‘Finally, she'll get help.' No help," her mother recalls.

Lynda Thorogood says she's been wracked with guilt since her daughter's death. But she says she's benefited greatly from therapy -- which she recommends for anyone dealing with similar circumstances.

With today Bell's "Let's Talk" Day, Thorogood says she hopes people will talk about mental illness, so that sufferers can ask for help without worries about stigma.

"It's a hidden epidemic and until we get it out of the shadows we are not ever going to bring out the solutions."

Peter and Martha Campbell lost two troubled sons to suicide. The family recalled that both sons developed major psychiatric illness at the age of 17.

Thomas Campbell killed himself in 2005, and three years later, younger brother George also committed suicide.

Wife Martha, who is a nurse, said the loss was "totally devastating."

The Campbells, who have four other children, are now on a mission to raise awareness about mental illness and emphasize that there is hope.

"It happens in normal families, to normal people," said Peter Campbell, who is also a doctor.

With a report from CTV Toronto's Janice Golding and Dana Levenson