Catherine Zeta-Jones' public fight with Bipolar Disorder II has proactively taken her into treatment for the second time in as many years, TMZ reports. The 43-year-old Oscar winner checked into rehab on Monday, as a source tells TMZ, it's for "maintenance" purposes.

Zeta-Jones was last seen in public on April 22, escorting her husband, actor Michael Douglas, on the red carpet at the 40th Anniversary Chaplin Award Gala at Lincoln Center. With Michael at her side, she looked to be in excellent health. But Douglas was flying solo at last weekend's White House Correspondent's Dinner. 

Zeta-Jones' rep, Cece York, told PEOPLE "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." 

A source told PEOPLE that Zeta-Jones was planning a return to treatment so that doctors could monitor her medication for the disorder. A friend said "There was no problem. This was just a good time to do it. She is in between projects. This has always been a part of the plan. She would manage her health. She is vigilant about it."

The buxom mother of two previously checked into the New Caanan, Connecticut Silver Hill Hospital for bipolar disorder in April of 2011, telling PEOPLE at the time, "This is a disorder that affects millions of people and I am one of them. 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." 

Zeta-Jones has also battled smoking, trying electronic cigarettes a few months after she initially checked herself into treatment in 2011. It was a way to support husband, Douglas, who was himself trying to kick the nasty habit as he underwent treatment for Stage IV throat cancer. 

Jones was last seen in theaters earlier this year in the disappointing Russell Crowe and Mark Wahlberg thriller, Playing for Keeps. She'll return to the big screen in July when she co-stars in Reds 2 with Anthony Hopkins and Bruce Willis. Douglas will head to the Cannes Film Festival in a couple weeks for his upcoming HBO biopic Behind the Candelabra starring Matt Damon.