In an exclusive interview, Marais tells The Weekly she traces the on-set of her condition to the death of her father when she was only twelve years old.
"I was diagnosed at one point with bipolar," Jessica, 29, says in a wide-ranging interview. "I have developed ways to talk myself down from any ledges I find myself on. And I am very lucky that I have a very patient partner who supports me.
"I just think it's important to talk about depression. It's nothing to be ashamed of. And the more we talk about it as a community, the more we remove the stigma."
The former Packed To The Rafters and current Love Child actress will next month play the title role of Carlotta in an ABC telemovie about Australia’s most famous transsexual entertainer.
In the June issue of The Weekly, Jessica recalls the day her father died in front of her from a heart attack and wonders whether it triggered her bipolar. She was only twelve years-old at the time. She adds her partner, actor James Stewart, also a Packed To The Rafters alumni, has been a rock for her, and their two-year-old daughter Scout an important new focus in her life.
"My bipolar is actually very manageable," she says in the interview. "And having a child to pull me out of it has made all the difference in the world."
Sometimes referred to as the "creative curse", bipolar is a common condition which has been thought to have affected many high-functioning creative types throughout history – including Ernest Hemingway, Vincent Van Gogh and the author Graeme Greene.
Australia's pre-eminent authority on depression, the Black Dog Institute, describes bipolar as "a set of 'mood swing' conditions, the most severe of which used to be called manic depression."
On its website, which also features a self-test, Black Dog says there are "milder and more severe" forms of the condition which sometimes manifests itself in wild mood swings – from euphoric highs to crushing lows.
Recently, other high-profile sufferers of depression, including Ian Thorpe and high-profile TV producer, Adam Boland, have bravely shared their experiences in the public sphere.