Major Depressive Disorder is a condition characterized by one or more Major Depressive Episodes without a history of Manic, Mixed, or Hypomanic Episodes. These Major Depressive Episodes are not due to a medical condition, medication, abused substance, or Psychosis. If Manic, Mixed, or Hypomanic Episodes develop, the diagnosis is changed to Bipolar Disorder.
A person who suffers from a major depressive disorder (sometimes also referred to as clinical depression or major depression) must either have a depressed mood or a loss of interest or pleasure in daily activities consistently for at least a 2 week period. This mood must represent a change from the person’s normal mood. Social, occupational, educational or other important functioning must also be negatively impaired by the change in mood. For instance, a person who has missed work or school because of their depression, or has stopped attending classes altogether or attending usual social engagements.
A depressed mood caused by substances (such as drugs, alcohol, medications) is not considered a major depressive disorder, nor is one which is caused by a general medical condition. Major depressive disorder generally cannot be diagnosed if a person has a history of manic, hypomanic, or mixed episodes (e.g., a bipolar disorder) or if the depressed mood is better accounted for by schizoaffective disorder and is not superimposed on schizophrenia, a delusion or psychotic disorder. Typically the diagnosis of major depression is also not made if the person is grieving over a significant loss in their lives (see note on bereavement below).
Clinical depression is characterized by the presence of the majority of these symptoms:
- Depressed mood most of the day, nearly every day, as indicated by either subjective report (e.g., feeling sad or empty) or observation made by others (e.g., appears tearful). (In children and adolescents, this may be characterized as an irritable mood.)
- Markedly diminished interest or pleasure in all, or almost all, activities most of the day, nearly every day
- Significant weight loss when not dieting or weight gain (e.g., a change of more than 5% of body weight in a month), or decrease or increase in appetite nearly every day.
- Insomnia or hypersomnia nearly every day
- Psychomotor agitation or retardation nearly every day
- Fatigue or loss of energy nearly every day
- Feelings of worthlessness or excessive or inappropriate guilt nearly every day
- Diminished ability to think or concentrate, or indecisiveness, nearly every day
- Recurrent thoughts of death (not just fear of dying), recurrent suicidal ideation without a specific plan, or a suicide attempt or a specific plan for committing suicide
In addition, for a diagnosis of major depression to be made, the symptoms must not be better accounted for by Bereavement, i.e., after the loss of a loved one, the symptoms persist for longer than 2 months or are characterized by marked functional impairment, morbid preoccupation with worthlessness, suicidal ideation, psychotic symptoms, or psychomotor retardation.
Completed suicide occurs in up to 15% of individuals with severe Major Depressive Disorder. There is a fourfold increase in deaths in individuals with this disorder who are over age 55. Individuals with this disorder have more pain and physical illness and decreased physical, social, and role functioning.
Alcoholism and illicit drug abuse dramatically worsen the course of this illness, and are frequently associated with it. Dysthymic Disorder often precedes the onset of this disorder for 10%-25% of individuals. This disorder also increases risk of also having Panic Disorder, Obsessive-Compulsive Disorder, Anorexia Nervosa, Bulimia Nervosa, and Emotionally Unstable (Borderline) Personality Disorder.
Associated Laboratory Findings
No laboratory test has been found to be diagnostic of this disorder. Sleep EEG abnormalities are evident in 40%-60% of outpatients and in up to 90% of inpatients with this disorder. The most frequent EEG sleep abnormalities are reduced rapid eye movement [REM] latency, increased REM density, reduced slow-wave sleep, and impaired sleep continuity. In some depressed individuals, hormonal disturbances have been observed, including elevated glucocorticoid secretion (e.g., elevated urinary free cortisol levels or dexamethasone nonsuppression of plasma cortisol) and blunted growth hormone, thyroid-stimulating hormone, and prolactin responses to various challenge tests. In some individuals, functional brain imaging shows increased blood flow in limbic and paralimbic regions and decreased blood flow in the lateral prefrontal cortex. Depression beginning in late life is associated with alterations in brain structure, including periventricular vascular changes (suggesting vascular depression).
Lifetime prevalence for this disorder in the general population is 10% to 25% for women and from 5% to 12% for men. In any year, 5% to 9% of women will have this disorder and from 2% to 3% of men will have it. The prevalence rates for this disorder appear to be unrelated to ethnicity, education, income, or marital status. In childhood, boys and girls are equally affected. However, in adolescence and adulthood, this disorder is twice as common in females as in males.
This disorder may begin at any age, with an average age at onset in the mid-20s. Some individuals have isolated episodes that are separated by many years without any depressive symptoms, whereas others have clusters of episodes, and still others have increasingly frequent episodes as they grow older. After the first episode of this disorder, there is a 60% chance of having a second episode. After the second episode, there is a 70% chance of having a third, and after the third episode, there is a 90% chance of having a fourth. About 5%-10% of individuals with this disorder subsequently develop Bipolar I Disorder. The acute onset of severe depression, especially with psychotic features and psychomotor retardation, in a young person without prepubertal psychopathology is more likely to predict a bipolar course. A family history of Bipolar Disorder may also be suggestive of subsequent development of Bipolar Disorder.
In two-thirds of cases, the Major Depressive Episode ends with complete recovery. For individuals that have only a partial recovery, there is a greater likelihood of developing additional episodes of this disorder and of continuing the pattern of partial interepisode recovery. Individuals that have pre-existing Dysthymic Disorder prior to the onset of this disorder are more likely to have additional Major Depressive Episodes, have poorer interepisode recovery, and have more difficult to treat Major Depressive Episodes. One year after the diagnosis of this disorder, 40% have no mood disorder; 20% are partially recovered; and 40% still have symptoms that are sufficiently severe to meet the criteria for a full Major Depressive Episode. The severity of the initial Major Depressive Episode appears to predict persistence. Chronic general medical conditions are also a risk factor for more persistent episodes. Among those with an onset of depression (depression treatment in Dubai & Abu Dhabi) in later life; there is evidence of subcortical white matter hyperintensities associated with cerebrovascular disease. These vascular depressions are associated with greater neuropsychological impairments and poorer responses to standard therapies.
Episodes of this disorder often follow a severe psychosocial stressor, such as the death of a loved one or divorce. Stressors may play a more significant role in the precipitation of the first or second episode of this disorder and play less of a role in the onset of subsequent episodes. Chronic medical conditions and Substance Dependence (particularly Alcohol or Cocaine Dependence) may contribute to the onset or exacerbation of this disorder.
First-degree biological relatives of individuals with Major this disorder are 1.5-3 times more likely to develop Major Depressive Disorder. They also have an increased risk of having Alcohol Dependence, Anxiety Disorder (e.g., Panic Disorder, Social Phobia), and Attention-Deficit/Hyperactivity Disorder compared with the general population.
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