Risk Factors

According to a major surveys, more than 13% of Americans experience major depression disorder over the course of their lifetimes. Furthermore, an estimated 18 million Americans experience major depression each year. Depression is second only to high blood pressure as a chronic condition encountered by primary care doctors. Depression is an illness that can afflict anyone, regardless of age, race, class, or gender. A third of all depressed people consider suicide, and 9% attempt it.

Gender and Depression

Depression in Women. At any given time, 5 - 9% of women are depressed, compared to 1- 3% of men. In one study, nearly half of all women surveyed had experienced depression at some point in their lives and over half of those who suffered from it had sought treatment. Women are also more apt to have multiple types of depression (dysthymia and major depression). [For more information, see box: Depression in Women.]

Depression in Men. Depression is not rare in men. In fact, prepubescent boys are more likely than girls of the same age to be depressed. Older men are also at much higher risk for suicide and, as with women, they are at risk for health complications of depression. Some evidence suggests that men are more apt than women to mask their depression by using alcohol, which may result in a lower reported (but not actual) incidence of depression in men. Some Swedish experts have suggested that men with depression might be identified with the following indicators:

• Low tolerance to stress
• Behaviors such as "acting out" and being impulsive
• A history of alcohol or substance abuse
• A family history of depression, alcohol abuse, or suicide

Depression is less reported in the male population, but this may be caused by male tendency to mask emotional disorders with behavior such as alcohol abuse.

Age and Depression

Depression in Children and Adolescents. Children between the ages of 12 and 16 are at high risk for depression. Studies suggest that 3 –5% of children and adolescents suffer from depression, and 10 – 15% have some depressive symptoms. Depression before puberty is more likely to occur in boys and after puberty in girls.

Depression in Adults. Surveys indicate that depression usually begins around the age of 30, although people do not generally seek treatment until they are about 33 years old. Statistics also suggest that depression is becoming more common among middle-aged people aged 45 to 64 years. According to a 2005 survey, middle-aged adults have the highest lifetime risk for depression.

Depression in the Elderly. Studies suggest that 5 – 14% of the elderly population suffer from some form of depression. In addition, the elderly are highly vulnerable to suicide. Elderly people comprise 13% of the US population but account for 18% of all suicide deaths.

Social Status and Economic Considerations

The role of society and economics has specific implications for women. [See Box Depression in Women.] Being in a low socioeconomic group is a major risk factor for depression in anyone. Money, of course, allows greater access to good medical care, but this factor does not fully explain the higher rates of depression in impoverished people. People at any income level are likely to be depressed if they have poor health and are socially isolated. Some studies suggest that Western cultural attitudes that link income to social status may play a significant role in the connection between poverty and depression:

• In one British study, actual poverty or unemployment increased the duration of any existing depression, but it did not appear to play any important causal role. Feelings of financial insecurity, however, both caused and prolonged depression.
• Another study reported that Mexican adults who immigrated to America had half the psychiatric illnesses as did Mexican-Americans born in the U.S., regardless of their income. But the longer the immigrants lived in the US, the greater their risk for psychiatric problems. Traditional influences of Mexican culture and social ties, then, appeared to protect newly arrived immigrants from mental illness, even when they were poor. Eventually, however, the consequences of Americanization added to poverty and led to feelings of alienation and inferiority.

Family History

Depression in family members increases the risk for depression in other family members. For example, studies report that depression for even one or two months in a mother increases the risk for depression in her children. The more severe the maternal depression, the higher the risk for depression in the children. In a perpetuating cycle, being depressed as a child increases the risk for depression during adulthood. In such cases, genetic or environmental factors or both may be responsible. Spouses of partners with depression are themselves at higher risk for depression.

Consequences of Loss and Trauma

Patients who have had serious bouts of depression usually cite a stressful life event as the precipitating factor for their illness. Adverse events during childhood pose a higher risk for depression in adulthood. In one study, parental divorce, physical abuse, and frightening experiences were particularly associated with onset of depression in adulthood. Only divorce was associated with recurrence, however.

Adverse events in adulthood also trigger depression. Losing a spouse through divorce or death is a major risk factor for depression in anyone. In fact, recent loss of a loved one is the most frequently reported precipitant of acute depression. All major (and even minor) losses, however, cause grief reactions. People who develop acute or chronic depression after a loss may have predisposing factors, including genetic or biologic ones, which make them more vulnerable. The existence or absence of a strong social network of family, friends, or both also has a major positive or negative effect, respectively, on recovery. Most people are able to cope with the emotional pain and eventually move beyond it without becoming chronically depressed. [See: Ruling out Grief and Loneliness in the diagnosis section of this report.]

Traumatic events such as abuse or even natural disasters can cause severe immediate or delayed depression from which recovery takes a long time.

Accompanying Medical Disorders

Severe or Chronic Medical Conditions. Any chronic or serious illness that is life threatening or out of a person's control can lead to depression.

Thyroid Disease. Thyroid disease can cause depression; however, it may be misdiagnosed as depression and go undetected.

Headaches. Studies have reported a strong association between depression and headaches, including chronic tension-type and migraine. Some experts believe that a syndrome of migraine headaches (and also possibly tension-type), anxiety, and depression, is caused by common factors, such as abnormalities in chemical messengers, particularly dopamine or serotonin.

Stroke. Having a stroke increases the risk of developing depression.

Medications

A number of drugs taken for chronic problems cause depression. Among them are pain relievers for arthritis, cholesterol-lowering drugs, medications for high blood pressure and heart problems, and bronchodilators used for asthma and other lung disorders.

Smoking

There is a significant association between cigarette smoking and a susceptibility to depression. People who are prone to depression face a 25% chance of becoming depressed when they quit smoking, and this increased risk persists for at least 6 months. What's more, depressed smokers are unlikely to stop smoking. Only about 6% remain smoke-free after a year. Smokers with a history of depression are not encouraged to continue smoking, but rather to keep a close watch on recurrence of depressive symptoms if they do stop smoking. The antidepressant bupropion (Wellbutrin), which is approved for helping people quit smoking (marketed under the name Zyban), is proving to be very useful in helping smokers to quit.

Anxiety Disorder

Chronic depression is a frequent companion to anxiety disorders. In one study, up to 96% of patients with depressive disorders experienced concurrent anxiety. More than two-thirds of people with obsessive-compulsive disorder, a common anxiety disorder, also suffer from depression.

Personality Characteristics and Disorders

Some evidence suggests that certain personality styles, which include an intense need for close relationships and concern for disapproval or need for control, pose a high risk for depression, particularly after an adverse life event. In line with these findings, the following specific personality disorders have been associated not only to a first episode of depression, but also to relapses:

• A person with borderline personality disorder acts impulsively and has a poor self-image and unstable relationships. In one study, patients with borderline personality disorder and major depression were more likely than those with either condition alone to plan and attempt suicide.
• An individual with an avoidant personality avoids strangers and unfamiliar situations.

(Personality disorders, as opposed to emotional disorders, are those with abnormal behavioral patterns rather than abnormal emotions.)

Insomnia and Sleep Disorders

Sleep abnormalities are an integral part of depressive disorders, with more than 90% of depressed patients experiencing insomnia. Although stress and depression are major causes of insomnia, insomnia may also increase the activity of the hormones and pathways in the brain that can produce emotional problems. Even modest alterations in waking and sleeping patterns can have significant effects on a person's mood. Persistent insomnia may even predict the future development of emotional disorders. Some investigators, in fact, are exploring the possibility of preventing psychiatric disorders by early recognition and treatment of insomnia.

Risk Factors for Seasonal Affective Disorder

Seasonal affective disorder (SAD) affects about one in 20 adults. About 80% of people who suffer from SAD are women. People who live in the north are more apt to experience SAD than are Southerners.