Margot Kidder, Louis Lane in 'Superman,' bipolarism activist, dead at 69

The first one Kidder and Reeve in the first Superman film which came out in 1978

Margot Kidder, the Canadian actress who starred as a salty and cynical Lois Lane opposite Christopher Reeve in the "Superman" film franchise of the 1970s and 1980s, has died.

According to the Associated Press, the actress died Sunday at her home in Livingston, Montana.

Kidder had her own struggles for a time, though she seemed to overcome them.

Diagnosed with bipolar disorder, Kidder was a proponent of the no-psychology-without-biology view of mental health; for her, nutrient therapy and other complementary and alternative treatments were preferable to psychiatric drugs. She campaigned for her brother, John Kidder, a farmer from Ashcroft, who was running in Okanagan Coquihalla for the Liberal party. I'll miss you Margo Kidder. At the age of 14, she made her first suicide attempt, noting in her diary that she had extreme mood swings and that things would be bad one day, but fine the next. From there, she kicked off a career that included movies such as The Gravy Train, Black Christmas, The Great Waldo Pepper and The Amityville Horror.

Her last project was the film The Neighborhood with Danny Aiello, which came out earlier this year. She was best known for her role as Lois Lane in the "Superman" movies of the '70s and '80s.

Marlon Brando, Gene Wilder, Robert Redford, Rod Steiger and Gene Hackman were among her leading men who she shared the screen with.

Actress Margot Kidder is seen here with her Superman co-star Christopher Reeve.

In 1996, Margot reportedly went missing for four days and was later found by a homeowner, The Independent reported at the time.

Smart, funny, and absent a public persona, Kidder somehow stayed open to the world despite the sort of head-turning fame that eventually overwhelms so many public figures.

Kidder told PEOPLE five months later that the root of most of her problems - which included "mood swings that could knock over a building" - was manic depression.

Kidder is survived by her daughter, Maggie McGuane and two grandchildren. The Canadian-born actress had also dated Canadian prime minister Pierre Trudeau.