In 2012, mood and other behavioral health disorders were the most common diagnoses for Medicaid-covered and uninsured hospital stays in the United States (6.1% of Medicaid stays and 5.2% of uninsured stays).A study conducted in 1988 to 1994 amongst young American adults involved a selection of demographic and health characteristics. A population-based sample of 8,602 men and women ages 17–39 years participated. Lifetime prevalence were estimated based on six mood measures:

major depressive episode (MDE) 8.6%,
major depressive disorder with severity (MDE-s) 7.7%,
dysthymia 6.2%,
MDE-s with dysthymia 3.4%,
any bipolar disorder 1.6%, and
any mood disorder 11.5%. Research
Kay Redfield Jamison and others have explored the possible links between mood disorders – especially bipolar disorder – and creativity. It has been proposed that a "ruminating personality type may contribute to both [mood disorders] and art. "Jane Collingwood notes an Oregon State University study that

"looked at the occupational status of a large group of typical patients and found that those with bipolar illness appear to be disproportionately concentrated in the most creative occupational category. They also found that the likelihood of engaging in creative activities on the job is significantly higher for bipolar than nonbipolar workers".In Liz Patereks article "Bipolar Disorder and the Creative Mind" she wrote

"Memory and creativity are related to mania. Clinical studies have shown that those in a manic state will rhyme, find synonyms, and use alliteration more than controls. This mental fluidity could contribute to an increase in creativity. Moreover, mania creates increases in productivity and energy.
Classification
Depressive disorders
Major depressive disorder (MDD), commonly called major depression, unipolar depression, or clinical depression, wherein a person has one or more major depressive episodes. After a single episode, Major Depressive Disorder (single episode) would be diagnosed. After more than one episode, the diagnosis becomes Major Depressive Disorder (Recurrent). Depression without periods of mania is sometimes referred to as unipolar depression because the mood remains at the bottom "pole" and does not climb to the higher, manic "pole" as in bipolar disorder.Individuals with a major depressive episode or major depressive disorder are at increased risk for suicide. Seeking help and treatment from a health professional dramatically reduces the individuals risk for suicide. Studies have demonstrated that asking if a depressed friend or family member has thought of committing suicide is an effective way of identifying those at risk, and it does not "plant" the idea or increase an individuals risk for suicide in any way. Epidemiological studies carried out in Europe suggest that, at this moment, roughly 8.5 percent of the worlds population have a depressive disorder. No age group seems to be exempt from depression, and studies have found that depression appears in infants as young as 6 months old who have been separated from their mothers.Depressive disorder is frequent in primary care and general hospital practice but is often undetected.