Depression is a normal human emotion that is experienced periodically in the form of “sadness,” “disappointment,” “grief,” or being “down in the dumps.” It is not uncommon to experience these feelings, particularly if environmental experiences are unrewarding, stressful, negative, or aversive. However, factors such as the frequency and duration of stressful life experiences, attribution style (or way of interpreting events), absence of environmental rewards, and a lack of coping resources influence whether these normal human experiences become symptomatic and evolve into a depressive disorder.

According to the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM—IV—TR), the two primary diagnostic criteria for major depressive disorder (MDD) are depressed mood and loss of interest or pleasure in most activities. At least one of these symptoms must occur for a duration of at least 2 weeks. Secondary symptoms include significant appetite change or weight loss or gain, sleep disturbance, psychomotor agitation or retardation, fatigue or energy loss, feelings of worthlessness or guilt, attention or concentration difficulties, and recurrent thoughts of death and/or suicide. Some depressed persons also may have psychotic symptoms (i.e., hallucinations or delusions). Typically, these symptoms are associated with increased depression severity, longer depressive episodes, and greater incapacity, and they are more resistance to treatment. The purpose of this entry is to provide information about the prevalence of depression and its effects on life functioning, risk factors associated with depression, and assessment strategies and treatment methods.

Prevalence and Impact of Depressive Disorders

The lifetime risk of MDD is between 10% and 25% for women and 5% and 12 % for men. There is some evidence that the incidence of depression and suicidal behavior is increasing across generations. For example, depression is now believed to be more frequent in adolescence than in adulthood. Within primary care medical settings, depression is possibly the most commonly experienced psychiatric problem. From 10% to 29% of patients in these settings have a depressive disorder and psychologists believe that clinical depression is largely unrecognized in this context.

Episodes of major depression are associated with extensive disruptions of normal functioning. These disruptions include exacerbation of medical illness and impaired physical health; diminished ability to concentrate, reason, and problem solve; decreased participation in pleasurable and rewarding activities; and problems with interpersonal relationships. The experience of a major depressive episode greatly increases the likelihood that future depressive episodes will occur. Major depression also increases vulnerability to other psychiatric problems such as anxiety disorders and alcohol abuse. The direct cost (e.g., health care and medication) of treating clinical depression is about $400 million to $500 million annually.

Depression Risk Factors

A variety of factors account for the greater incidence of depression observed among women relative to men. Women face different stressors (e.g., physical and sexual abuse) than men and have greater stress reactivity. They also differ in their cognitive coping styles and self-report strategies. Biological factors including increased responsiveness to hormonal changes such as those associated with the menstrual cycle and postpartum period also play a role.

Other risk factors include Caucasian ethnicity, marital separation or divorce, prior depressive episodes, poor physical health or medical illnesses, low socioeconomic status, unemployment, loss of a loved one, and family history of depression. Although major depression may develop at any age, the average age of onset is 15 to 19 years in females and 25 to 29 years for males. The average age of onset has been decreasing steadily over the past 3 decades. The elderly do not appear more susceptible to depression.

Depression Assessment Strategies

Numerous strategies have been developed to assess depression and related constructs such as attribution style, hopelessness, and depressive vulnerability. Approaches for assessing depression include unstructured or structured interviews, self-report measures, behavioral observation, and functional analysis. The level of skill and training necessary to use these strategies is quite variable, ranging from the minimal skill required to administer and interpret a self-report measure, to the moderate skill needed to conduct and evaluate a structured interview, to the extensive skill required to perform a comprehensive functional analysis of depressive symptoms.

Unstructured and Structured Interviews

Clinical interviews include unstructured and completely flexible approaches, semistructured approaches that provide some direction while maintaining a degree of flexibility (e.g., intake form), and structured methods that are more restrictive and goal directed. Most contemporary practitioners use a combination of assessment procedures that include some type of intake form or checklist and some unstructured procedures to allow a degree of flexibility. In recent years concerns about the reliability and validity of unstructured interviews has led psychologists to place greater emphasis on more structured procedures. Among the more common structured interviews are the Structured Clinical Interview for DSM-IV—Patient Version, Anxiety Disorders Interview Schedule, Schedule for Affective Disorders and Schizophrenia, and the Hamilton Rating Scale for Depression.

Self-Report Measures

Self-report measures of depression are useful as screening instruments, as one component of a comprehensive diagnostic process, as tools for monitoring progress across treatment sessions, and as outcome measures for assessing the effectiveness of various psychosocial and pharmacological interventions. Scales are available to assess a tremendous range of content areas, including affective, verbal-cognitive, somatic, behavioral, and social symptoms of depression. At present, there are at least 80 measures designed to assess depression and related constructs, and the majority of these instruments have adequate to excellent psychometric properties. The most commonly used measures include the Beck Depression Inventories, Hamilton Depression Inventory, Center for Epidemiological Studies’ Depression Scale, Harvard Department of Psychiatry/National Depression Screening Day Scale, Reynolds Depression Screening Inventory, Minnesota Multiphasic Personality Inventory-2 Depression Scale (MMPI-2), and the Personality Assessment Inventory. All of these assessment instruments are acceptable for use in clinical practice, but the latter two are more comprehensive and more costly personality inventories.

Observational Methods

Observational methods are used to measure the frequency and duration of observable behaviors that are symptomatic of depression. Some symptoms reflect behaviors that occur in excess of normal behavior (e.g., crying, irritation, and agitation). Others include deficits in normal behavior (e.g., minimal eye contact, psychomotor retardation, decreased participation in recreational and occupational activities, and disruption of sleeping, eating, and sexual behaviors).

Depressed individuals generally exhibit a slower and more monotonous rate of speech, take longer to respond to the verbal behavior of others, exhibit an increased frequency of self-focused negative remarks, and use fewer “achievement” and “power” words in their speech. Compared to nondepressed individuals, depressed individuals smile less frequently, make less eye contact, hold their head in a downward position more frequently, and are rated as less competent in social situations. Couples research suggests that when one partner is clinically depressed, interactions are more apt to involve conflict. Depressed mothers tend to be less active and playful and exhibit shorter eye-gaze durations with their children.

Several useful coding methods have been designed to assess both verbal and nonverbal behaviors. These methods will often involve video- and audiotape review, but more practically can involve direct observations in home, school, or employment contexts. Some behavioral coding systems require substantial training to achieve reliable and valid results.

Functional Analysis

Functional analysis is the process of identifying important, controllable, and causal environmental factors that may be related to the etiology and maintenance of depressive symptoms. Performing a functional analysis is an essential step prior to initiating an appropriate behavioral intervention. Functional analysis involves the operational definition of undesirable (nonhealthy) depressive behavior(s) such as lethargy, social withdrawal, crying, alcohol abuse, and suicide potential. Strategies for conducting functional analyses include interviews with the patient and significant others, naturalistic observation, and the manipulation of specific situations that result in an increase or decrease of target behaviors. Often functional analysis involves some form of daily monitoring (e.g., frequency of occurrence, the context and consequences of depressive behaviors).

When performing a functional analysis the therapist is concerned with identifying the function the depressed behavior serves for an individual (i.e., why the depressed behavior occurs). According to behavioral theory, depressive behavior occurs because reinforcement for healthy behavior is minimal or because reinforcement for depressive behavior is excessive. In other words, depressed behavior may be maintained because it leads to pleasant consequences (e.g., other people give the depressed person attention and sympathy and assume his or her responsibilities) or because it results in the removal of aversive experiences (e.g., they allow the depressed person to avoid unpleasant or stressful activities).

A functional analysis also may be performed by cognitively-oriented therapists to gain an understanding of the maladaptive thought processes they believe to be critical in eliciting depressive affect. Strategies such as thought-monitoring logs or thought-sampling methods can be used to identify the specific thought patterns elicited by certain environmental events and to determine how these cognitions correspond to depressive mood states. Behavioral interventions for depression also incorporate some form of functional analysis to help in generating specific treatment goals.

Depression Treatment Strategies

Treatment options for major depression generally include pharmacological, alternative, or psychotherapeutic approaches. Tricyclic antidepressants, monoamine oxidase inhibitors, selective serotonin reuptake inhibitors (SSRIs), and atypical antidepressants such as buproprion and venlafaxine have been shown to be effective in lessening clients’ feelings of depression. In general, tricyclic antidepressants, SSRIs, and the newer atypical agents are the pharmacological treatments of choice. SSRIs and atypical antidepressants are generally preferred when they are effective because they have fewer and less aversive side effects.

For more severe depressions where other interventions have not been useful, electroconvulsive shock therapy may provide some relief. Although the evidence is unclear at this stage, alternative treatments such as St. John’s Wort and omega-III fatty acids may have promise as effective treatments for clinical depression.

Psychotherapy for major depression generally includes cognitive-behavioral, problem-solving, interpersonal, supportive, psychodynamic, psychoanalytic, and couple and family approaches. Of these interventions, cognitive-behavioral, problem-solving, and interpersonal approaches have received the most support.

Research has demonstrated that both antidepressant medication and short-term psychotherapy can be effective in treating clinical depression. Some research suggests that in the short-term, antidepressant medications may be more effective than interpersonal psychotherapy or cognitive-behavioral therapy for individuals with less severe depression. Other studies suggest cognitive therapy is more effective than tricyclic medication in reducing depressive symptoms and in altering people’s views of themselves, the world, and the future. Although a combined treatment might logically seem to be more effective than psychotherapy or medications alone, research has not yet demonstrated that multi-modal therapy has an added benefit in treating clinical depression. However, several studies suggest this strategy may be promising among patients with more severe (chronic) depression. There are some data to suggest that depressed patients who respond to psychotherapy may be less likely to relapse following treatment termination than patients treated using only antidepressant medication.

Randomized clinical trials have been conducted to evaluate the efficacy of psychosocial interventions for depression. Using standard criteria, cognitive, behavioral, and cognitive-behavioral interventions are efficacious (i.e., empirically validated) and problem-solving therapy is possibly efficacious. It is difficult to draw conclusions about the relative therapeutic utility of these interventions, the generalizability of the findings, and the mechanisms responsible for the beneficial change. That is because researchers have used inconsistent operational definitions and measurement criteria, have provided inadequate sample descriptions, have used inappropriate statistical strategies, and have other methodological limitations.

Many factors are associated with a negative (or limited) treatment response, however, including increased severity and chronicity of depression, family history of depression, presence of a personality disorder, coexistent Axis I conditions (e.g., anxiety disorders), perceived social stigma, increased cognitive and/or social dysfunction, marital problems, decreased treatment expectations, and double depression (or a major depressive episode superimposed on a preexisting dysthymia).

Most individuals with clinical depression receive their treatment in primary care medical settings from their primary care physicians. Many depressed individuals are undiagnosed or misdiagnosed in this setting. Furthermore, the quality of care for depression for those who are correctly diagnosed is moderate to low compared with that provided in more traditional mental health settings. There is minimal evidence that the specific medication prescribed is related to the treatment outcome. A more serious problem is that only 11% of primary care medical patients receive an adequate dosage and duration of antidepressant medication. Even when primary care physicians are provided with psychiatric consultations, antidepressant pharmacotherapy still is not adequately provided to a majority of patients.

In primary care medical settings, psychotherapy and pharmacotherapy have much to offer patients who are diagnosed with depression. However, these treatments either are not readily integrated into today’s managed health care system, which does not support lengthier psychotherapy, or are often used inappropriately (e.g., prescription of inadequate doses of antidepressant medications). One potential solution seems to be increased use of collaborative care management programs. These programs involve an intensive primary care team (e.g., depression care manager, primary care physician, psychiatrist, and primary care expert) that provides a more integrated and effective treatment protocol to depressed patients. Given the training required to become proficient in interpersonal and cognitive psychotherapy and difficulties in administering these treatments in a time-efficient manner, the most feasible and effective psychosocial treatments for depression in primary care may be problem-solving therapy or behavioral activation. Indeed, there is no convincing research to suggest these abbreviated and more practical interventions can’t address depressive symptom patterns to the same extent as more comprehensive cognitive-behavioral or interpersonal approaches.

In conclusion, depression is a prevalent and debilitating psychiatric disorder. Psychologists have a solid understanding of many of the risk factors associated with depression and a number of effective, empirically-validated treatment strategies are available. These include cognitive-behavioral therapy, interpersonal psychotherapy, problem-solving therapy, and antidepressant medications that include tricyclic medications, SSRIs, and newer atypical antidepressants such as venlafaxine and cymbalta.

Nevertheless, many patients do not receive adequate treatment for depression in primary care settings and many patients are dissatisfied with the treatment they do receive for depression. Effective management of depressive symptoms via antidepressant medications is questionable, and antidepressants demonstrated as efficacious in clinical trials are not administered effectively under conditions of routine care. For this reason, psychotherapy for depression is preferred over pharmacotherapy in many cases. Psychotherapy appears to be equally or in some cases more effective than pharmacotherapy, and less patient relapse may occur following psychotherapy.


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