Both Montgomery and her husband suffered from depression. (Canadian Press)

The granddaughter of Lucy Maud Montgomery has revealed a long and closely held family secret about how the author of Anne of Green Gables died.

In an essay in the Globe and Mail on Saturday, Kate Macdonald Butler said Montgomery committed suicide. She said there was a note, which she's never seen, but she was told it asked for forgiveness.

Macdonald Butler said it seemed appropriate to lift the secrecy on the 100th anniversary of the publishing of Montgomery's first and most famous book. She was inspired to reveal the truth because of a series published in the Globe on mental health, and she hoped it would help get rid of the stigma of mental illness.

Society has the idea that depression happens to "other people," she wrote, and in particular that it doesn't happen to our "heroes and icons."

Lucy Maud Montgomery published about 500 short stories and poems, and 20 novels, 19 of which are set on P.E.I.

Montgomery community buzzing with the news

There has been a lot of discussion in the online Montgomery community about the article, said Mark Leggot, chair of the L. M. Montgomery Institute in Charlottetown.

Leggot said comments among the 600 members of the Kindred Spirits List have been varied.

"Things like, 'You know there has been rumours in the community for years,' or 'I'm so surprised and shocked,' and a very common one is, 'It's nice to see the family use such a prominent figure to educate people about mental illness and the issues associated with that,'" he said.

"It's actually quite a range of things that to a large degree reflect the issues that Kate rose in the article."

Leggott said he didn't know it was coming, but he was not surprised that such a creative and well-loved author as L. M. Montgomery suffered from a mental illness.

Mental health group applauds announcement

The news that Montgomery killed herself will likely encourage families of people who have committed suicide to get help, said Reid Burke, executive director of the Canadian Mental Health Association on P.E.I.

'This is not a new issue.'— Reid Burke, Canadian Mental Health Association

Burke said Macdonald Butler's essay brings home the message that mental illness affects people of all types, even famous authors.

'[It's] very positive to see her stepping forward, making sure that people understand that this is not a new issue. This is an issue that people dealt with for years," he said.

"After all this time, it is actually becoming more acceptable, when they come forward and talk about how her grandmother struggled. There is that kind of myth that if you don't talk about it, it will go away. And it doesn't go away. It affects families and the survivors for years."

Burke said the family's decision to reveal how Montgomery died shows that great strides have been made in recent years to de-stigmatize mental illness.

Both Montgomery and her husband Ewan Macdonald suffered from depression. She died in 1942 at the age of 67. He died a year later.

Macdonald Butler said she discussed revealing Montgomery's suicide with her family and that they agreed.

CBC News spoke with Dr. Mary Rubio, Canada's best-known Montgomery scholar, who declined to be interviewed but did say the note and the context around it will be part of her upcoming Montgomery biography.