Last reviewed: 2 Sep 2023
Last updated: 09 Nov 2022

This page compiles our content related to depression. For further information on diagnosis and treatment, follow the links below to our full BMJ Best Practice topics on the relevant conditions and symptoms.



Major depressive disorder is characterized by at least 5 symptoms and can be classified along a spectrum of mild to severe. Depressive symptoms include depressed mood, anhedonia, weight changes, libido changes, sleep disturbance, psychomotor problems, low energy, excessive guilt, poor concentration, and suicidal ideation. In some cases the mood is not sad, but anxious or irritable or flat.[2]

One of the most common pediatric psychiatric disorders, especially among girls during adolescence. It may be characterized more by irritability than sadness, and it often occurs in association with other conditions such as anxiety.[3]

Disruptive mood dysregulation disorder

Disruptive mood dysregulation disorder is a category of depressive disorders first diagnosed at 6 to 18 years of age, with age of onset before 10 years. It is characterized by the Diagnostic and Statistical Manual of Mental Disorders, fifth edition, text revision (DSM-5-TR) as severe and recurrent temper outbursts on average 3 or more times per week for at least 1 year, and a persistent irritable or angry mood for most of the day nearly every day between temper outburst.[2]

Includes common forms of depression, but lasting longer than acute major depressive disorder. The DSM-5-TR modified its classification system to include all chronic forms of depression under the single category persistent depressive disorder, which includes both chronic major depressive disorder and the previous category of dysthymic disorder (dysthymia), or chronic low-grade depression. The DSM-5-TR includes specifiers to identify different pathways to the diagnosis of persistent depressive disorder and various presentations based on severity and clinical characteristics.[2]

Postpartum depression is not recognized by current classification systems as a condition in its own right, but the onset of a depressive episode within 4 weeks of childbirth can be recorded via the peripartum-onset specifier in the DSM-5-TR.[2] In common usage, depressive episodes occurring within 6 to 12 months of delivery may be considered to be postpartum depression.

Characteristics of postpartum depression may include guilt about the depressive symptoms, ambivalent feelings toward the infant, impaired bonding, and obsessive ruminations, including intrusive thoughts about harming the infant. Postpartum depression should be distinguished from a minor mood disturbance (postpartum blues or "baby blues"), in which the symptoms generally resolve within 2 weeks.

Premenstrual syndrome (PMS) is characterized by cyclical, physical, and behavioral symptoms occurring in the luteal phase of the normal menstrual cycle (the period between ovulation and onset of menstruation). Premenstrual dysphoric disorder (PMDD) is a more severe variant that includes at least one affective symptom. Depression may coexist with PMS or PMDD in up to 50% of cases. A diagnosis of PMS or PMDD may predate a diagnosis of depression.[4]

Seasonal affective disorder (SAD) is a subtype of major depression and bipolar disorder, occurring with seasonal change over at least a 2-year period. Most commonly presents with onset of depression in the autumn or winter, and full remission of symptoms over the spring or summer. Lifetime estimates for depressive and bipolar disorders with a seasonal pattern average between 0.4% and 2.9% in US, Canadian, and UK community studies.[5][6][7] Some estimates may be as high 9.7%.[8] However, these differences are probably due to differences in the sampling and diagnostic criteria used.

A recurrent and often chronic mental illness, bipolar disorder is marked by episodes of hypomania or mania and depression, associated with a change or impairment in functioning. The long-term course of illness is characterized by a predominance of depression, although a history of at least one manic, hypomanic, or mixed episode is required to make the diagnosis of a bipolar disorder.

Bipolar I disorder: at least one manic episode.

Bipolar II disorder: has never had a full manic episode; at least one hypomanic episode and at least one major depressive episode.[2]

Bipolar disorder is an uncommon condition in children that becomes more frequent in teens, approaching the rate of frequency seen in adults.[9][10] The adult criteria describe a disorder of fluctuating mood cycles, consisting of episodes of elevated mood and increased activity or energy (mania) lasting at least 1 week, and episodes of lowered mood and activity (depression); an episode of mania is necessary for a diagnosis to be made. The diagnosis can be controversial, as criteria overlap with other childhood conditions such as ADHD and comorbid oppositional defiant disorder. 

Suicide is an important cause of death globally and a significant public health concern. An estimated 800,000 people die by suicide each year; it is the second leading cause of death among people aged 15 to 29 years.[11] Originally called suicide risk management, suicide risk mitigation aims to be a more realistic and compassionate approach.[12][13][14] It refers to the identification, assessment, intervention, and treatment of a person at risk of suicide. It is an ongoing process whether due to a mental illness or a life crisis. 



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