Catherine Zeta-Jones has checked into a treatment centre for her bipolar II disorder.

The 'Chicago' actress is expected to complete a 30-day program as a "proactive" measure to help with her condition, which can cause high and low mood swings as well as depression.

Cece Yorke, her representative, told People magazine: "Catherine has proactively checked into a health care facility.

"Previously Catherine has said that she is committed to periodic care in order to manage her health in an optimum manner."

Catherine, 43, first sought medical help in 2011 when she spent time in a Connnecticut-based mental health facility.

A friend of the star's added that she simply wants doctors to monitor her medication this time, saying: "There was no big problem. This was just a good time to do it. She is in between projects.

"This has always been part of the plan. She would manage her health. She is vigilant about it."

The Welsh beauty and her husband Michael Douglas - who have children Carys, 10, and Dylan, 12, together - were last seen in public a week ago at the Film Society of Lincoln Center's 40th Annual Chaplin Award Gala.

Michael then stepped out alone at the White House Correspondents Dinner on Saturday, just two days before Catherine checked into the facility.

The star has been open about her bipolar disorder in the past and strives to be a positive role model for women with mental health issues.

She said: "If my revelation of having bipolar II has encouraged one person to seek help, then it is worth it.

"There is no need to suffer silently and there is no shame in seeking help."