What is Bipolar II?

Catherine Zeta Jones has disclosed that she is receiving treatment for bipolar II disorder.

Catherine Zeta Jones has revealed that she sought treatment for manic depression Photo: REX FEATURES

Mental health professionals have identified four main subtypes of bipolar disorder that together are referred to as bipolar spectrum disorders: bipolar I, bipolar II, bipolar not otherwise specified, and cyclothymia.

Although symptoms vary significantly from person to person factors that differentiate the types of bipolar include the duration and intensity of the mood swings.

Depression is the primary characteristic of bipolar II. While those with bipolar II do have "up" periods, these episodes are less marked. Instead of full-blown mania, people with bipolar II experience hypomania, a milder form of mania. Studies show that women are slightly more likely to have bipolar II.

Though a person with bipolar II may deny that anything is wrong, loved ones will probably notice that he or she seems agitated, is flying off the handle more often, or seems unusually upbeat.

Bipolar II is sometimes mistaken for depression because the hypomanic periods are harder to detect. Over time, without treatment, hypomania -- the "up" period -- can progress into mania or turn into a depressed state.