Depression is one of the most devastating of all psychiatric disorders. It is the leading cause of disability in the United States and the world for people between ages 15 and 44 (Kessler et al., 2005; World Health Organization, 2004).
Defining and Diagnosing Depression
As much as it is important to know what depression is, it is equally important to recognize what it is not. Research literatures suggest that depression (across the spectrum of its manifestations) is most directly captured by three prominent features:
- a depressed mood,
- a lowering of self-esteem or self-worth, and
- an increase in self-criticism.
Phenomenologically, this weighting distinguishes depression from anxiety Opens in new window—which is most commonly experienced as a sense of uncertainty, apprehension, insecurity, and fear, as well as hyperarousal (which can then lead to appetite and sleep changes).
In grief Opens in new window, something of value to the sufferer (e.g. a partner, an ideal) is lost, but, in pure instances, the sufferer’s self-esteem is not reduced (only in about one-third of grieving individuals does depression, with its associated drop in self-esteem feature, develop).
As depression and anxiety Opens in new window (in particular) commonly co-exist (with the presence of each increasing the occurrence of the other), many clinicians are tempted to view anxiety Opens in new window and depression as synonymous. It is pertinent, for our purpose, to note that the phenomenological distinction of grief Opens in new window from depression is important, particularly in prioritizing treatment strategies.
Distinguishing meaningful expressions of depression is a less clear-cut process, but the obvious first task here is to contemplate what might distinguish normal depression and clinical depression.
Normal fluctuations in mood, even if they distress us, are appropriate, and may even be desirable; they can easily be quelled by such harmless antidotes as an early night to bed or an agreeable evening with convivial company.
To feel alive is to think, feel, and react both to our environment and to the people around us. When we stop thinking, feeling, and reacting, we become like automatons or robots.
When asked, more than 90% of people in the community have had episodes of depression — defined as “a state of depressed mood, lowered self-esteem and feeling hopeless, helpless, and pessimistic about the future”.
Most report that such states only last minutes to several days.
Such feeling blue states can then be described as normal depression, allowing that depression can be a normal reaction to the vicissitudes of everyday life.
A depressed mood can exist on its own, or, if accompanied by a number of concomitant features (discussed below), be defined as a syndrome. Such a state (e.g. feeling depressed, not sleeping well, and experiencing other mood-state concomitants does not, of necessity, establish disorder status.
For depression to be a disorder, it not only has to have some level of severity, but it must also be persistent, and impair function. Operationalizing each of those parameters is less clear-cut.
Persistence (of at least 2 weeks) is formalized in systems such as the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) (American Psychiatric Association, 1994) and appears (in practice) to be useful, in that normal depression usually lasts minutes to days.
Impairment should generally be interpreted in a commonsense way, in that the individual should have greater difficulty in engaging in tasks at work or at home.
Attempts to distinguish normal and clinical depression across other parameters, including severity, are more difficult as depressed mood severity (like pain severity) is very dependent on the subjective attributional style of any individual.
As indicated, for most people, an episode of normal depression (whether mild or severe) is relatively brief. It comes to an end either because it is destined to remit spontaneously and rapidly, or because the individual implements restitutive coping repertoires (e.g. discussing issues with and receiving support from friends, seeking distraction in work or hobbies) that serve to restore mental equilibrium.
Although many clinically depressed people also engage in such behaviors, relief from depression tends only to be brief or superficial. Thus, the distinction of clinical depression on the basis of differing coping repertoires is unhelpful, as coping secondary to the depression reflects a range of contributing factors.
Similarly, differences in stressors or stressor severity are not particularly helpful in defining clinical depression.
For every event or enormity that can occur in life which might trigger an episode of clinical depression, there will be people in the community who do not develop depression in response to that event, or, if they do become depressed, experience a rapid remission.
Diagnosis and Symptoms
As noted in the previous section, a key fey feature of clinical depression (sometimes called major depressive disorder (MDD)) is failure to experience a spontaneous remission. Why?
We argue that, for those who have the more biological types of depression, such a state is sustained and maintained by perturbed biological processes, while for those who have non-melancholic disorders, their personality style and social factors more tend to maintain the condition.
Thus, while understanding what separates those who are vulnerable (i.e. who develop clinical depression) from those who are resilient to depression, it is equally important to contemplate why the clinically depressed individual has failed to experience a spontaneous remission.
Clinical depression is predictably more severe than normal depression, with mood expressions including suicidal preoccupations as well as somatic features (such as sleep disturbance or poor concentration) being prominent.
Our clinical descriptions do not convey fully the sheer range and depth of problems encountered by sufferers, who consistently report that it can be one of the most devastating events that anyone can experience.
Authors who have been afflicted use descriptors such as “a black hole” or “dark shadow”.
Other terms (such as “black night of the soul”, “agony of mind or spirit”, and “anguish of the soul”) reflect the inner turmoil accompanying the more biological clinical depressive disorders, often despite a lack of outward signs.
While all depressive conditions are ultimately disorders of mood and loss of pleasure, many expressions encapsulate feelings of despair, wretchedness, and misery that obliterate all hope for recovery.
It is no wonder then that people refer to their battle with depression when describing their rehabilitation from a depressive episode.
Clinical depression is also a disorder of motivation, reflected in an inability to initiate purposeful activity, and to recover from everyday life stressors.
Clinically depressed patients often suffer from lassitude and apathy, accompanied by or oscillating with overwhelming feelings of regret and guilt.
By the time diagnosis of clinical depression is made, most sufferers have repeatedly encountered numerous unsuccessful attempts at starting or trying to complete tasks that they would otherwise be capable of accomplishing.
As clinical depression erodes a person’s capacity to give and receive affection, it eats into the sense of connection with others, leaving sufferer feeling simultaneously abandoned, isolated, and discomforted by an enforced sense of solitude.
As episodes are commonly recurrent, with sudden or insidious onsets, and lasting weeks to years, a progressively erosive process may, in itself, change the way an individual relates to others, perceives the world, and reacts to stress.
Clinical depression can go through many phases. Its onset may follow a period of anxiety and stress. Once established, it may plateau, or vary across the days and weeks. Improvements may be partial (termed remission) or complete (recovery), and further episodes can occur when the individual has only partially improved (relapse) or following a depression-free interval (recurrence).
Patients can present at any time during such cycles, perhaps most commonly when they are at their worst or after some improvement when they have regained enough energy to seek help. In the latter phase, they often primed to experience benefit from appropriate management.
The formal presence of clinical depression can be estimated in several ways. As noted earlier, both DSM-IV and the International Classification of Diseases, 10th edition (ICD-10) (World Health Organization, 1992) focus on the severity, duration, persistence, and recurrence of depressive symptoms, with the presence of such features used to assign an overall diagnosis of (say) major or minor depression (DSM model), or mild, moderate, or severe depression (ICD-10).
In order to meet a diagnosis of clinical depression under the current DSM-IV classification, an individual would have to fulfill the criteria of five or more symptoms (listed below), with at least one having to be either depressed mood and/or loss of interest or pleasure in most activities.
In addition, this state would need to last for more days than not over at least a 2-week period and be accompanied by significant impairments in social and/or work functioning. Other symptoms include:
- weight loss or weight gain,
- insomnia or hypersomnia,
- psychomotor retardation or agitation,
- recurrent thoughts of death or suicidal ideation,
- fatigue or loss of energy,
- feelings of worthlessness or guilt, and
- poor concentration or indecisiveness.
A similar criteria-based approach allows other DSM diagnoses to be made (e.g. major depression with melancholic features and dysthymia). Such criteria sets are useful in establishing a shared lexicon for superficial clinical communication but, as noted earlier, lack the precision necessary to advance clinical decision-making and research.
Prevalence and Life Course
The lifetime prevalence of clinical depression (or majar depressive disorder) is estimated at 16.9% (Kessler et al., 2003).
A 12-year prospective study indicated that for any given year of assessment the prevalence rates were 4–5%, but that over the whole 12-year period rates were 24.2% of women and 14.2% of men, which were twice as high as previous estimates (Pattern, 2009).
Relationship conflict is associated with increased risk for clinical depression: Women experiencing conflict in their marriages are 25 times more likely to become depressed (Hammen, 2004).
In addition, approximately 8–12% of women experience postpartum depression (Heneghan et al. 2000). The greatest risk for clinical depression occurs for individuals between 18 and 44 years of age, and the lowest risk is for those aged 60 and over. Over a 6-month period, 50% of children and adolescents and 20% of adults report some symptoms of depression (Kessler et al. 2001).
The lifetime prevalence rates of clinical depression for females are twice those of males. Rates for attempted suicide are higher for females, but completed attempts are higher for males, who prefer more lethal methods of suicide (e.g., guns and hanging as compared to medication overdose or wrist cutting).
The highest suicide risk is for the separated, divorced, and recently widowed, and the lower risk is for single and married individuals. Living alone and urban environment confer greater risk than cohabiting or rural residence.
Those individuals whose families show a history of suicide, alcoholism Opens in new window, and depression, or who perceive that they do not have good social support, are at greater risk.
Greater risk is also found for individuals with a personal history of self-harm or injury, with less social connectedness, and with perceptions of themselves as a burden to others (Joiner, Van Orden Witte, & Rudd, 2009).
- Genetic/Biological Factors
Estimates of the heritability for depression range between 37% and 66%, with early-onset depression marked by greater heritability. The concordance for monozygotic twins for clinical depression is about 50%, whereas the concordance for dizygotic twins is about 35% (Kaeler, Moul, & Farmer, 1995).
Kendler, Neale, Kessler, Heath, and Eaves (1992) estimate heritability for clinical depression at 39%, indicating some biological predisposition, but reflecting that other factors (such as life events, developmental history, and coping skills) are more prominent.
Early onset depression is associated with a family history of depression, implicating genetic factors in early onset (Nierenberg et al., 2007).
Genetics interacts with socialization, so that individuals at higher genetic risk are more likely to become depressed after experiencing stressful events during childhood; this interaction supports the stress-diathesis model of depression (Kendler, Kessler, et al., 1995).
Depression is higher among individuals whose parents divorced, separted, or died during the individual’s childhood (Blatt & Homann, 1992). Although loss of a parent is associated with greater risk for later depression, the way in which the loss was handled may be more important: Decreased warmth, care, and attention following the loss are associated with increased risk of depression (Harris, Brown, & Bifulco, 1986). Sexual abuse—or any abuse—is also associated with increased risk for depression (Bifulco, Brown, & Adler, 1991).
There is evidence that a combination of parental cognitive styles (negative attributional style), negative inferential feedback, and emotional maltreatment confer greater risk for depression later in life.
All these factors mediate the effects of stressful life events in leading to depression (Alloy et al. 2004; Panzarella, Alloy, & Whitehouse, 2006). In particular, socialization experiences that affect cognitive styles may lead to greater vulnerability to depression.
Clinical depression has high comorbidity with other disorders, including panic disorder, agoraphobia, social anxiety disorder (social phobia), generalized anxiety disorder, posttraumatic stress disorder, and substance abuse.
As indicated, marital conflict (for both males and females) is an excellent predictor of depression; indeed, some clinicians recommend marital/couple therapy as the treatment of choice for patients presenting with depression associated with relationship discord (Beach, Dreifuss, Franklin, Kamen, & Gabriel, 2008).
Physical illness, especially in the elderly, is correlated with depression. For individuals with chronic depression or a history of major depressive disorder (MDD), there is increased risk of Alzheimer’s disease, stroke, and poor outcome of HIV disease. Elderly people who are depressed are more likely to die earlier (Janzing, Bouwens, Teunisse, Vant’ Hof, & Zitman, 1999).
Several physical conditions are associated with depression; these may be:
- pharmacological (steroid use, amphetamine/cocaine/alcohol/sedative withdrawal),
- endocrine (hypothyroidism and hyperthyroidism, diabetes, Cushing’s disease),
- infectious (general paresis, influenza, hepatitis, AIDS), or
- neurological (multiple sclerosis, Parkinson’s disease, head trauma, cerebrovascular disorder) (See Akiskal, 1995, for a more complete list.)
In addition, clinical depression is highly correlated with personality disorders, although the diagnosis of a personality disorder may be uncertain until depression is alleviated.
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