Risk Factors:

According to major surveys, major depressive disorder affects nearly 15 million Americans (nearly 7% of the adult population) in a given year. While depression is an illness that can afflict anyone at any time in their life, the median age of onset is 32 (although adults age 49 -54 years are the age group with the highest rates of depression.). Other major risk factors for depression include being female, being African-American, and living in poverty.

Depression in Women

Women, regardless of nationality, race, ethnicity, or socioeconomic level, have twice the rate of depression than men. (Women with depression also oftentimes have accompanying eating disorders, such as anorexia nervosa and bulimia. [For more information, see In-Depth Report #49: Eating disorders.]) While men are more likely than women to die by suicide, women are twice as likely to attempt suicide.

The causes of such higher rates of depression appear to be a mix of sociocultural and hormonal factors:

• Sociocultural Factors. Stress from work, family responsibilities, and childcare can play a role in triggering depression in women. In addition, many women live in poverty and have a history of sexual abuse, both of which are risk factors for developing depression.
• Hormonal Factors. Hormonal changes that accompany womenâ ' s developmental and reproductive processes may play a role in depression. Hormonal influences are particularly associated with: Puberty. While both boys and girls have similar rates of depression before puberty, girls have twice the risk for depression once they reach puberty.
• Menstruation. While many women experience mood changes around the time of menstruation, a small percentage of women suffer from a condition called premenstrual dysphoric disorder (PMDD). PMDD is a specific psychiatric syndrome that includes severe depression, irritability, and tension before menstruation. [For more information, see In-Depth Report #79: Premenstrual syndrome.]
• Pregnancy and Childbirth. Hormonal fluctuations that occur during pregnancy, especially when combined with relationship stresses and anxiety, can contribute to depression. About 10 - 15% of women, especially first-time mothers, experience post-partum depression, a severe depression (sometimes accompanied by psychosis) that occurs within the first year after giving birth. The rapid decline of reproductive hormones that accompany childbirth is likely to play the major role in postpartum depression in susceptible women. Studies suggest that women who are more sensitive to hormone fluctuations are at greater risk for postpartum depression if they have a personal or family history of depression. Miscarriage also poses a risk for depression.
• Perimenopause and Menopause. Hormonal fluctuations that can trigger depression also occur when a women is transitioning to menopause (perimenopause). Sleep disruptions are also common during perimenopause and may contribute to depression. Once women pass into menopause, depressive symptoms generally tend to wane. [For more information, see In-Depth Report #40: Menopause.]

Depression in Men

Depression is not rare in men. In fact, white men over age 85 have the highest rates of suicide of any group. 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 research suggests that depression in men is associated 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.

Depression in Children and Adolescents

Depression can occur in children of all ages, although adolescents have the highest risk. Risk factors for depression in young people include having parents with depression, particularly if it is the mother who is depressed. Early negative experiences and exposure to stress, neglect, or abuse also pose a risk for depression. Sometimes depression develops after a physical illness. In adolescents, feeling alienated from parents is a strong predictor for depression.

Adolescents who have depression are at significantly higher risk for substance abuse, recurring depression, and other emotional and mental health problems in adulthood.

Studies suggest that 3 - 5% of children and adolescents suffer from clinical depression, and 10 - 15% have some depressive symptoms.

Symptoms for depression in children often differ from those in adults and may include:

• An inability to enjoy favorite activities
• Persistent sadness
• Increased irritability
• Complaints of physical problems, such as headaches and stomachaches
• Poor performance in school
• Persistent boredom
• Low energy
• Poor concentration
• Changes in eating and/or sleeping patterns

Risk for Suicide in Adolescents. Suicide is the third most common cause of death among adolescents, and is one of the most devastating events than can happen to a family. Suicide is most commonly associated with depression in young people but it is also linked with anxiety, psychosis, substance abuse, or impulsivity. More girls attempt suicide but more boys succeed, most often because they choose guns or violent methods while girls tend to overdose, which is more treatable. Nevertheless, attempts are major risk factors for a later suicide. Any expression of suicidal intent should be treated very seriously.

The following are danger signs in young people:

• Withdrawal from friends
• Sudden decrease in school performance
• Loss of interest in activities that were previously pleasurable
• Unusual irritability
• Unusual changes in sleep or eating habits

Risk factors for suicide include a history of neglect or abuse, history of deliberate self-harm, a family member who committed suicide, access to firearms, and living in communities where there have been recent outbreaks of suicide among young people. A romantic break-up is often the trigger for a suicidal attempt in teenagers. Feeling connected with parents and family can help protect young people with depression from suicide.

Parents should not hesitate to seek professional help for their children if they suspect they are thinking about killing themselves. This is a medical emergency and requires immediate treatment.

Behavioral therapies and antidepressants are promising treatments for preventing suicide but need study. There has been a decline in adolescent suicides over the past decade, which some researchers attribute to the increased use of antidepressants in this population. However, recent evidence has indicated that antidepressants can also raise the risk for suicidality (suicidal thoughts and behavior) in some people. Children, adolescents, and young adults who are prescribed antidepressant medication should be carefully monitored by both their parents and doctor, especially during the first few months of treatment, for any worsening of depression symptoms or changes in behavior. [See "Suicide Risk" and "Antidepressant Medications" in Medication section of this report.]

Depression in the Elderly

About 1 - 5% of elderly people suffer from depression. However, the rate increases significantly for those who have other chronic health problems, especially medical conditions such as Alzheimerâ ' s, Parkinsonâ ' s disease, heart disease, and cancer that interfere with functional abilities. Depression occurs in about 12 - 14% of elderly people who require home healthcare or hospitalization. In addition, older people often have to contend with significant stressful life changes such as the loss of a spouse. Suicide in the elderly is the third-leading cause of death related to injury. Men account for the majority of these suicides, with divorced or widowed men at highest risk.

Medical Conditions Associated with Increased Risk of Depression

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. Many medications taken for chronic medical problems can 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.

Thyroid Disease. Hypothyroidism (a condition caused when the thyroid gland does not produce enough hormone) can cause depression. However, hypothyroidism may also be misdiagnosed as depression and go undetected.

Chronic Pain Conditions. Studies have reported a strong association between depression and headaches, including chronic tension-type and migraine. Some research indicates 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. Fibromyalgia and other chronic pain syndromes are also associated with depression.

Stroke and Other Neurological Conditions. Having a stroke increases the risk of developing depression. Also, patients with Parkinson's disease, spinal cord injuries, and other similar problems that impair movement or thinking are associated with depression.

Heart Failure. Patients with heart failure or patients who have suffered a heart attack may also be at increased risk for depression.

Insomnia and Sleep Disorders. Sleep abnormalities are an integral part of depressive disorders, with many 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.

Diabetes. There appears to be an association between depression and type 2 diabetes. Recent research suggests that depression may modestly increase the risk for diabetes, and that diabetes may increase the risk for depression.

Other Risk Factors

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 some smokers to quit.