It is associated with a group of disorders called leukodystrophies.

When that happens, as in Bruce's case, it is called bipolar type 2 disorder.

Depression that lasts a long time is called major depressive disorder.

Some older people experience dysthymic disorder, sometimes called minor depression.

It is also the first line of defense for a rare disorder called stiff-person syndrome.

This may lead to a type of metabolic disorder called porphyria.

Those are the classic symptoms of a common disorder called restless legs syndrome.

In the 20th century, the term was largely replaced by that of depression, which is also called major depressive disorder.

Some believe she may have been born with the disorder called Down syndrome but it has never been proved.

When people are very sad, and for a long time, the person could have a serious mental illness called depression or Bipolar disorder.