Depression is the state of feeling unhappy, “being down in the dumps”, or having “the blues”, with the associated feelings of feeling unmotivated, and not feeling satisfied with things that ordinarily are naturally enjoyable, such as eating, sleeping, concentrating on things, exercising, or positive life events. Other associated feelings are feelings of low self-esteem, excessive guilt, feeling tired moving and thinking, and thinking more about death.
Because depression can range in intensity from a low grade state to one that overtakes the person’s existence, there are different levels of depression, categorized as major depressive disorder and dysthymia. There are different types of depression, some due to “unipolar” depression, and bipolar depression, in which the person has experienced not only depression, but also hypomania and mania. The descriptions in this page are of unipolar depression; bipolar depression is similar in signs and symptoms but will be discussed further in the page on bipolar disorder.
One of the major reasons seek out psychiatrists is to treat depression. According to the DSM-V, (the Diagnostic and Statistical Manual of Mental Disorders, edition 5), the rule book professionals use to diagnose mental conditions, the most serious type of depression is Major Depressive Disorder. In this condition, at least five of the following symptoms have been present during a 2-week period; at least one of the symptoms is either (1) depressed mood or (2) loss of interest or pleasure.
- Depressed mood most of the time, demonstrated in subjective report (e.g., feels sad, empty, hopeless) or observation made by others (e.g., appears tearful). (Note: In children and adolescents, can be irritable mood.)
- Decreased interest or pleasure in all, or almost all, activities most of the time (as indicated by either subjective report or observation).
- Significant weight loss when not dieting or weight gain or decrease or increase in appetite nearly every day.
- Insomnia or increased sleeping nearly every day.
- Psychomotor agitation or retardation most of the time, observable by others (increased restlessness, or the opposite, acting or speaking too slowly or after long pauses).
- Fatigue or loss of energy nearly every day.
- Feelings of worthlessness or excessive or inappropriate guilt (which may be delusional) most of the time, but not just being sad about being sick.
- Diminished ability to think or concentrate, or indecisiveness, most of the time.
- Recurrent thoughts about death, recurrent suicidal thoughts with or without a specific plan, or a suicide attempt.
Other than major depressive disorder, other forms of depression include Persistent Depressive Disorder (Dysthymia), a more more persistent but often lower grade form of depression. In this condition, there is depressed mood most of the time over 2 years, with the addition of 2 of the following 6 criteria:
- low self-esteem
- Insomnia or hypersomnia (oversleeping)
- Poor appetite or overeating
- Low energy or fatigue
- Poor concentration or difficulty making decisions
Another type of depressive disorder is Premenstrual Dysphoric Disorder. In the majority of menstrual cycles, at least five symptoms must be present in the final week before the onset of menses, start to improve within a few days after the onset of menses, and become minimal or absent in the week after the menses occurs.
One (or more) of the following symptoms must be present:
Marked affective lability (instability) occurs (e.g., mood swings; feeling suddenly sad or tearful, or increased sensitivity to rejection).
Marked irritability or anger or increased interpersonal conflicts.
Marked depressed mood, feelings of hopelessness, or self-deprecating thoughts.
Marked anxiety, tension, and/or feelings of being keyed up or on edge.
One (or more) of the following symptoms must additionally be present, to reach a total of five symptoms when combined with mood symptoms above.
- Decreased interest in usual activities (e.g., work, school, friends, hobbies).
- Subjective difficulty in concentration.
- Lethargy, easy fatigability, or marked lack of energy.
- Marked change in appetite; overeating; or specific food cravings.
- Hypersomnia or insomnia.
- A sense of being overwhelmed or out of control.
- Physical symptoms such as breast tenderness or swelling, joint or muscle pain, a sensation of “bloating,” or weight gain.
For every patient,, the illness begins with a single episode; however, in most cases, the episodes eventually become recurrent (estimates of recurrence range from ~ 50% within the first year to up to 85% during a lifetime; Mueller et al. 1999).
Most scenarios of major depressive disorder tend to be cyclical. The length of a depressive episode is in the range of 5–6 months, with approximately 20% of episodes becoming chronic (i.e., lasting beyond 2 years).
First-degree family members of individuals with MDD have a risk for MDD that is 2 to 4 times higher than that of the general population. Relative risks appear to be higher for early-onset and recurrent forms. Heritability is approximately 40%, with the personality trait neuroticism (defined as a predisposition toward negative affective states such as depression, anxiety, anger, and shame) accounting for a substantial portion of this genetic liability (Sullivan et al. 2000).
Neuroticism (is a well-established risk factor for the onset of MDD, and high levels appear to render individuals more likely to develop depressive episodes in response to stressful life events.
Features associated with lower recovery rates include long course duration, severity of symptoms, including psychotic symptoms, prominent anxiety, and co-existing personality disorders. The risk for recurrence falls slowly as time in remission increases and is higher when the preceding episode was severe, especially in younger individuals and in those who have already experienced multiple episodes (Kanai et al. 2003). The persistence of even mild depressive symptoms during remission is a powerful predictor of recurrence.
Essentially, all major non-mood-related psychiatric disorders increase the risk of an individual’s developing depression (Kessler et al. 1997). Major depressive episodes that develop against the background of another disorder often follow a more refractory course. Substance use, anxiety, and borderline personality disorders are among the most common of these, and the presenting depressive symptoms may obscure and delay their recognition (Kessler et al. 2005). However, sustained clinical improvement in depressive symptoms may depend on the appropriate treatment of underlying illnesses. Chronic or disabling medical conditions also increase risks for major depressive episodes. Such prevalent illnesses as diabetes, morbid obesity, and cardiovascular disease are often complicated by depressive episodes, which are more likely to become chronic than are depressive episodes in medically healthy individuals (McIntyre et al. 2012).
Adverse childhood experiences, particularly when there are multiple experiences of diverse types, comprise a set of potent risk factors for MDD. Stressful life events are well recognized as precipitants of major depressive episodes, but the presence or absence of adverse life events near the onset of episodes does not appear to provide a useful guide to prognosis or treatment selection.
Despite consistent differences between genders in prevalence rates for depressive disorders, there appear to be no clear differences by gender in phenomenology, course, or treatment response. The higher prevalence in females is the most reproducible finding in the epidemiology of MDD. Risks for suicide attempts are higher in women; however, risks for completion of suicides in women are lower. There are no consistent differences between genders in symptoms, course, treatment response, or functional consequences.
Similarly, there are no clear effects of current age on the course or treatment response of MDD. Some symptom differences exist, however, such that reverse vegetative symptoms are more likely in younger individuals, and melancholic symptoms, particularly psychomotor disturbances, are more common in older individuals. The likelihood of suicide attempts lessens in middle and late life, although the risk of completed suicide does not. Depressions with earlier ages at onset are more familial and are more likely to involve personality disturbances. The course of MDD within individuals does not generally change with aging. Mean times to recovery appear to be stable over long periods, and the likelihood of being in an episode does not generally increase or decrease with time.
Estimates of the lifetime prevalence of MDD vary from 4% to 30%. In the Western culture, the most generally accepted figure is 16%, with an range of variability between 15%–17% (Kessler et al. 2003). The 1-month prevalence in the National Comorbidity Study was estimated to be 6%.
Although over 90,000 references are identified when etiology and depression are searched in Medline, the etiology of major depression remains an enigma. Much is known and is being researched, yet consistently reproducible results remain on the horizon. One of the most helpful discussions for beginning an understanding of the complex etiologies behind a heterogeneous disorder such as major depression is in Perspectives of Psychiatry by McHugh and Slavney 1998).
There can be (at least) four perspectives to approaching and understanding depressive illnesses and phenomena. The biological perspective considers the increased genetic risk in affected family members, as well as biochemical and immunological factors such as inflammatory molecules and stress-related markers of the endocrine system. The behavioral perspective takes into account the role of motivated behaviors contributing to the clinical picture, including unhealthy lifestyle choices and related behaviors; smoking, drinking, unhealthy eating habits leading to obesity, and gambling are examples of behaviors that compromise moods and contribute to the etiology of major depression. Personality features and temperament contributing to mood disorders are captured in the dimensional perspective. Finally, the life-story perspective describes the influences that life events and environmental influences may have on the development of the disorder.