Catherine Zeta Jones has been treated for Bipolar disorder.
The Welsh actress checked into the Silver Hill Hospital in Connecticut last week for around five days.
Her representative said the illness—diagnosed as Bipolar II disorder—was triggered by the stress of her husband Michael Douglas's recent battle with cancer.
The spokesperson said: "After dealing with the stress of the past year, Catherine made the decision to check in to a mental health facility for a brief stay.
"She's feeling great and looking forward to starting work this week on her two upcoming films."
Bipolar disorder—also known as manic depression—is a mental illness where sufferers have elevated or irritable moods alternating with periods of depression. Bipolar II is marked by longer mood swings and more severe depression, and can be triggered by major life changes.
Michael, 66, underwent six months of intense chemotherapy and radiotherapy to treat a tumor in his throat before being given the "all clear" in January.
A friend of Catherine's told website People.com: "Catherine has had to deal with Michael's illness and that's been hard. She went in for a few days because she's about to start working, and wanted to make sure she's in top form, which she is."
Speaking about their relationship, Michael told OK! magazine: "I think you just spend the effort and time and don't take each other for granted. That probably is the most important thing."
The couple have two children together, Dylan, 10, and Carys, who will be eight next week.
Catherine, 41, is set to star in Playing the Field and Lay the Favorite, both of which are scheduled for release next year.