Which illness does actress Catherine Zeta Jones have?

The revelation that the seemingly unshakable actress Catherine Zeta-Jones has been diagnosed with bipolar II disorder illustrates the hallmarks of the disease.

Zeta-Jones suffering from depression, and despite initial apprehension, she spoke publicly about suffering from bipolar disorder. She sought treatment by checking herself into hospital in 2011, and again in 2013.

Bipolar disorder, also known as manic depressive illness, is a mental illness characterized by mood swings between the two psychological pulls of depression and euphoria. It can sometimes be controlled with medication and therapy.

Stress is one common trigger for bipolar disorder, according to the National Institutes of Mental Health. The condition can also be spotted if someone has a prolonged feeling of agitation, trouble sleeping, major changes in appetite, and thoughts of suicide.