Major depressive disorder overview

# Overview
Major depressive disorder a psychiatric disorder characterized by a pervasive low mood, loss of interest in usual activities, and a diminished ability to experience pleasure (anhedonia).
Depressive symptoms may affect quality of life more that the cardiac ejection fraction or cardiac ischemia or other illnesses.

# Historical Perspective
Clinical depression was originally considered to be a chemical imbalance in transmitters in the brain, a theory based on observations made in the 1950s of the effects of reserpine and isoniazid in altering monoamine neurotransmitter levels and affecting depressive symptoms.

# Classification
Based on the duration of symptoms, timing, and the presumed etiologies, depressive disorders are classified into 7 subtypes: major depressive disorder, persistent depressive disorder (or dysthymia), premenstrual dysphoric disorder, substance/medication-induced depressive disorder,  depressive disorder due to another medical condition, other specified depressive disorder, and unspecified depressive disorder.

# Pathophysiology
The exact pathogenesis of major depressive disorder is not fully understood.
However, it is thought that major depressive disorder is the result of decreased levels of serotonin, norepinephrine, and dopamine.

# Causes
Current theories regarding the causes of major depressive disorder can be broadly classified into two categories, Physiological and Sociopsychological.

# Differentiating Major depressive disorder from Other Diseases
Major depressive disorder must be differentiated from other causes of depressive symptoms.

# Epidemiology and Demographics
The one-year prevalence of major depressive disorder is approximately 7,000 per 100,000 (7%) of the overall population with marked differences by age groups.

# Risk Factors
Risk factors for clinical depression include genetic, temperamental, environmental, and psychological factors.

# Screening
According to theU.S. Preventive Services Task Force (USPSTF), screening for major depressive disorder is recommended in children and adolescents 12 to 18 years of age, in older adults, and in pregnant women (at least once during pregnancy and again 4-8 weeks after delivery).

# Natural History, Complications, and Prognosis
Common complications of [[major depressive disorder include alcohol or substance abuse, physical health problems, and suicide.

# Diagnosis

## Diagnostic Study of Choice
Major depressive disorder is diagnosed based on the DSM-V Diagnostic Criteria.

## History and Symptoms
Clinical depression can present with a variety of symptoms, but almost all patients display a marked change in mood, a deep feeling of sadness, and a noticeable loss of interest or pleasure in favorite activities.

## Physical Examination
Physical examination of patients with major depressive disorder is usually normal.

## Laboratory Findings
There are no diagnostic laboratory findings associated with major depressive disorder.

## CT scan
There are no gross CT scan findings associated with major depressive disorder.

## MRI
There are no MRI findings associated with major depressive disorder.

## Other Imaging Findings
There are no other imaging findings associated with major depressive disorder.

## Other Diagnostic Studies
A number of psychological tests can be used to help in the diagnosis and assessment of treatment efficacy in patients with major depressive disorder.

# Treatment

## Medical Therapy
The mainstay of treatment for major depressive disorder is pharmacologic therapy with serotonergic agents.

## Psychotherapy
There are a number of psychotherapies for depression, which may be provided individually or in a group format. Psychotherapy can be delivered by a variety of mental health professionals, including psychotherapists, psychiatrists, psychologists, clinical social workers, or psychiatric nurses.

## ECT
Electroconvulsive therapy (ECT), also known as electroshock or electroshock treatment, uses short bursts of a controlled current of electricity (typically fixed at 0.9 amperes) into the brain to induce a brief, artificial seizure while the patient is under general anesthesia.

## Surgery
Surgery is not the first-line treatment option for patients with . Surgery may be used for selected patients.

## Primary Prevention
There are no established measures for the primary prevention of major depressive disorder.

## Secondary Prevention
Effective measures for the secondary prevention of major depressive disorder include antidepressant maintenance therapy and psychotherapy.