major depressive disorder

major depressive disorder
Field	Psychiatry, Clinical psychology

major depressive disorder. It is a common and serious mood disorder characterized by persistent low mood and loss of interest, significantly impairing daily functioning. The condition is diagnosed based on criteria outlined in the Diagnostic and Statistical Manual of Mental Disorders, with symptoms lasting at least two weeks. Its global impact is substantial, contributing significantly to disability as measured by organizations like the World Health Organization.

Signs and symptoms

Core symptoms include a profoundly depressed mood and markedly diminished interest or pleasure in activities, known as anhedonia. Individuals often experience significant changes in appetite and body weight, alongside disturbances in sleep such as insomnia or hypersomnia. Psychomotor agitation or retardation is common, as are pervasive fatigue and feelings of worthlessness or excessive guilt. Impaired concentration and recurrent thoughts of death or suicidal ideation are critical symptoms, with severe cases potentially leading to psychosis featuring delusions or hallucinations. The Columbia Suicide Severity Rating Scale is sometimes used to assess risk. Many patients also report comorbid anxiety symptoms and various somatic complaints.

Causes

The etiology is understood as a complex interplay of genetic, neurobiological, and environmental factors. Family and twin studies indicate a significant heritability component, with research from institutions like the National Institute of Mental Health implicating variations in genes related to the serotonin system. Neurobiologically, theories involve dysregulation of monoamine neurotransmitters, hypothalamic-pituitary-adrenal axis hyperactivity, and reduced neuroplasticity in areas like the hippocampus and prefrontal cortex. Major life stressors, such as bereavement or unemployment, chronic medical conditions like cardiovascular disease, and substances including corticosteroids can precipitate episodes. The diathesis-stress model integrates these vulnerability and trigger factors.

Diagnosis

Diagnosis is primarily clinical, based on criteria in the DSM-5 published by the American Psychiatric Association. A diagnostic interview assesses for the presence of at least five of nine specific symptoms, including the core mood and anhedonia criteria. Clinicians use standardized tools like the Patient Health Questionnaire-9 or the Hamilton Rating Scale for Depression to gauge severity. It is crucial to rule out other conditions through differential diagnosis, such as bipolar disorder, persistent depressive disorder, adjustment disorder, and medical causes like hypothyroidism. The International Classification of Diseases provides an alternative diagnostic framework used globally.

Treatment

First-line treatment typically involves psychotherapy, pharmacotherapy, or a combination. Evidence-based psychotherapies include cognitive behavioral therapy, developed by Aaron T. Beck, and interpersonal psychotherapy. Common pharmacological treatments are antidepressants like selective serotonin reuptake inhibitors (e.g., fluoxetine), serotonin-norepinephrine reuptake inhibitors, and atypical agents such as bupropion. For treatment-resistant cases, options may include electroconvulsive therapy, transcranial magnetic stimulation approved by the U.S. Food and Drug Administration, or the NMDA receptor antagonist ketamine. Collaborative care models in settings like the Veterans Health Administration and lifestyle interventions addressing exercise and sleep hygiene are also important.

Epidemiology

It is a leading cause of disability worldwide, as highlighted in the Global Burden of Disease Study. Lifetime prevalence estimates vary but are commonly cited around 10-15% in many populations. It is approximately twice as common in women compared to men, with onset frequently occurring in early adulthood. Risk factors include a family history, adverse childhood experiences, and certain personality traits. High rates of comorbidity exist with other mental disorders, including generalized anxiety disorder and substance use disorder. Incidence appears to be increasing in younger cohorts in regions like North America and Europe.

History

Descriptions of melancholic states date back to ancient civilizations, including writings in Hippocrates' humoral theory. In the 19th century, Emil Kraepelin distinguished it from dementia praecox (later schizophrenia) within his classification of psychoses. The 20th century saw the advent of effective treatments with the accidental discovery of the first monoamine oxidase inhibitor, iproniazid, and the introduction of imipramine by Roland Kuhn. The development of the DSM-III by the American Psychiatric Association in 1980 established clearer operational criteria. Modern neuroscience research continues to evolve, driven by organizations like the National Alliance on Mental Illness and projects such as the Human Connectome Project.

Category:Mood disorders Category:Clinical psychology Category:Psychiatry