Mood disorders represent a broad spectrum of psychiatric conditions that primarily affect an individual's emotional state, causing significant disturbances in mood regulation.

These disorders are characterized by prolonged periods of either abnormally elevated mood or debilitating depression, often fluctuating in intensity and duration.

Classification and Overview

Mood disorders are generally classified into two principal categories: depressive disorders and bipolar disorders, as delineated by authoritative psychiatric manuals such as the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) and the International Classification of Diseases (ICD-10). Both categories comprise distinct disorders, differentiated by symptom patterns, course, and severity.

Depressive Disorders

Depressive disorders primarily involve persistent low mood and loss of interest or pleasure in usual activities. Several subtypes exist within this group:

Major Depressive Disorder (MDD)

Characterized by episodes of intense sadness or hopelessness lasting at least two weeks, coupled with symptoms such as fatigue, sleep disturbances, and impaired concentration. MDD significantly impairs daily functioning and may include psychotic features in severe cases.

Persistent Depressive Disorder (Dysthymia)

Marked by a chronic, less severe depressive mood persisting for at least two years. Although symptoms are milder than MDD, their prolonged nature results in considerable distress and functional impairment.

Disruptive Mood Dysregulation Disorder (DMDD)

Primarily diagnosed in children and adolescents, DMDD involves severe temper outbursts and chronic irritability, differentiating it from typical mood fluctuations in youth.

Seasonal Affective Disorder (SAD)

A form of depression related to seasonal changes, usually occurring in fall and winter, linked to decreased sunlight exposure.

Bipolar and Related Disorders

Bipolar disorders involve alternating episodes of mood elevation and depression, with mood states ranging from mania or hypomania to major depression. Key types include:

Bipolar I Disorder

Defined by the presence of at least one full manic episode, often accompanied by major depressive episodes. Mania is characterized by abnormally elevated mood, increased energy, decreased need for sleep, and sometimes psychotic symptoms. The severity of manic phases distinguishes Bipolar I from other types.

Bipolar II Disorder

Marked by at least one hypomanic episode—a milder form of mania without severe impairment—and one or more major depressive episodes. Hypomanic episodes do not include psychotic features and generally cause less functional disruption than mania.

Cyclothymic Disorder

A chronic mood disorder involving numerous periods of hypomanic symptoms and depressive symptoms that do not meet full criteria for mania or major depression, lasting for at least two years. Cyclothymia often precedes bipolar disorder and involves fluctuating, unstable mood.

Other Specified and Unspecified Mood Disorders

These categories include mood disturbances that do not fully correspond to the typical presentations of depressive or bipolar disorders but still cause clinically significant distress or impairment. This includes mixed episodes where symptoms of both mania and depression occur simultaneously or rapidly alternate.

Dr. Kay Redfield Jamison, a clinical psychologist and expert has argued, mood disorders — including depression and bipolar illness — are common, serious, and often disabling; careful diagnosis and individualized, competent treatment are critical to effective care.

Mood disorders encompass a diverse range of conditions characterized by significant and sometimes fluctuating mood disturbances. Depressive disorders predominantly involve prolonged low mood states, while bipolar disorders are defined by oscillations between mood elevation and depression. Subtypes like persistent depressive disorder, disruptive mood dysregulation disorder, and cyclothymic disorder further illustrate the heterogeneity within this category.