Depression occurs in up to 18 million Americans, affecting all racial, ethnic, and socioeconomic groups (more common in lower socioeconomic groups). It affects both sexes, but is more commonly diagnosed in women.

Children and the elderly can also be affected and are often not diagnosed. According to the United States Department of Health and Human Services, 1 in every 12 adolescents experiences major depression each year, and more than twice as many females than males are affected.

The causes of depression aren’t completely understood and are probably due to a combination of genetic, familial, biochemical, psychological, and social factors as well as medical conditions. The incidence of depression is higher among people who also have a family member with depression or who have attempted suicide, which suggests an inherited predisposition. Research using brain imaging suggests that depressed people have physical brain changes. Other research suggests that dysregulation in neurotransmitters and hormones influences the development of depression. Psychological causes (the focus of many nursing interventions) may include the feelings of helplessness, vulnerability, anger, hopelessness and pessimism, and low self-esteem. Developing depression may be related to dysfunctional character and behavior patterns and troubled personal relationships. In many cases, the individual identifies a specific personal loss or severe stressor that probably combines
with the person’s predisposition to provoke major depression.

Depression may be secondary to a specific medical condition—for example, metabolic disturbances, such as hypoxia and hypercalcemia; endocrine disorders, such as diabetes and Cushing’s syndrome; neurologic diseases, such as Parkinson’s and Alzheimer’s diseases; cancer (especially of the pancreas); viral and bacterial infections, such as influenza and pneumonia; cardiovascular disorders, such as heart failure; pulmonary disorders, such as chronic obstructive lung disease; musculoskeletal disorders, such as degenerative arthritis; GI disorders, such as irritable bowel syndrome; genitourinary problems, such as incontinence; collagen vascular diseases, such as lupus; and anemia.

Drugs prescribed for medical and psychiatric conditions as well as many commonly abused substances can also cause depression. Examples include some antihypertensives, psychotropics, opioid and nonopioid analgesics, antiparkinsonian drugs, numerous cardiovascular medications, oral antidiabetics, antimicrobials, steroids, chemotherapeutic agents, cimetidine, and alcohol.

The primary features of major depression are a predominantly sad mood and a loss of interest or pleasure in daily activities. The patient may complain of feeling “down in the dumps,” express doubts about his self-worth or ability to cope, or simply appear unhappy and apathetic. Symptoms tend to be more severe than those caused by dysthymic disorder, which is a milder, chronic form of depression. (See Dysthymic disorder.)

Other common signs and symptoms include:

• difficulty concentrating or thinking clearly

• distractibility and indecisiveness

• reduced psychomotor activity (for example, slowed speech)

• agitation and restlessness

• anxiety

• crying for no reason

• hostility and irritability (in men)

• lack of energy

• anhedonia (inability to experience pleasure)

• severe stress or loss

• sleep disturbances (for example, insomnia or early wakening)

• weight loss or gain for no reason

• constipation or diarrhea

• loss of interest in sex and sexual dysfunction

• suicidal thoughts or preoccupation with death.

The patient’s medical history may implicate a physical disorder or the use of prescription, nonprescription, or illegal drugs that can cause depression. Note that many of the characteristics of depression, such as changes in eating and sleeping patterns, fatigue, and problems with concentration, may also occur in chronic medical conditions.

• Suicide

• Anxiety

• Heart disease—patients are twice as likely to develop cardiac disease within 10 years of being diagnosed with depression (Depressed patients are more likely to die after having a myocardial infarction.)

• Depressed immune response

• Substance and alcohol abuse

• Occupational and school problems

• Interpersonal relationship problems

• Social isolation

For characteristic findings in patients with this condition, see Diagnosing major depression, page 98.

• Psychological tests, such as the Beck Depression Inventory, may help determine the onset, severity, duration, and progression of depressive symptoms.

• Laboratory tests to exclude medical conditions may include:

— complete blood count

— thyroid function studies

— toxicology tests to detect alcohol and other substances

— cytochrome P450 test: pharmacogenetic test that indicates an individual’s ability to metabolize certain medications. (It’s used to help tailor and predict the patient’s response to antidepressants and other drugs.)

About 70% to 80% of people with depression demonstrate improvement in symptoms within a few months of starting treatment. Treatment may include:

• psychotherapy to help identify stressors, conflicts, and losses and to problem solve

• cognitive behavioral therapy to help the patient identify and change negative thoughts, beliefs, and behavior

• group and family therapy