Catherine Zeta-Jones has revealed she has undergone treatment in a mental health clinic for her bipolar illness. "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 to treat her Bipolar II disorder," said her publicist. The disorder, also known as manic depression, is marked by dramatic shifts in moods. Bipolar II is not as severe as Bipolar I. Zeta-Jones has been under particular stress this year because of husband Michael Douglas' battle with throat cancer, and a tough court struggle with his ex-wife over profits from his film Wall Street 2, notes ABC News. Click for more on Zeta-Jones.