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Depression Overview Everyone feels sad at times or inexplicably tearful or just plain "down." These uncomfortable feelings are part of life. But when they persist, affecting the way one eats and sleeps, feels about oneself, and thinks about family, friends, and work, then they are not just a part of life, but symptoms of a clinical illness. Three types of depressive disorders are most common. A major depression interferes with the ability to work, study, sleep, eat, and enjoy once pleasurable activities. Such a disabling episode may happen only once in a lifetime, but more commonly it occurs several times. Dysthymia is the term used to describe long-term symptoms that, while not disabling, keep one from functioning well or feeling good. Another type of depressive condition is bipolar disorder, also called manic-depressive illness, which is characterized by severe highs (mania) and lows (depression). In any one-year period, 9.5 percent of the population, or about 18.8 million American adults, suffer from a depressive disorder. Depression can strike anyone regardless of age, ethnic background, socioeconomic status, or gender. However, large-scale studies have found that depression is about twice as common in women as in men. The economic cost of these disorders is high--some estimates put the annual workplace cost of depression in America at over $40 billion. But the cost in terms of human suffering is incalculable. Depressive illnesses bring pain and suffering not only to those who have the disorder but also to those who care about them and for them. Indeed, one individual's depression can reverberate throughout an entire family. Also, most suicides are the result of untreated depression. But today much of this suffering is unnecessary. Over the past 20 years, biomedical research has shed considerable light on depression, and, as a result, new medications and psychosocial therapies exist to help depressed people. As more people recognize that these illnesses are treatable, more are rediscovering their sense of optimism and purpose through appropriate treatment. This section includes more on:
Need-to-know anatomy Despite years of research, no one knows precisely how the biology of depression works. Indeed, it may vary among different people. Nonetheless, three major biological systems--the nervous system and neurotransmitters, the limbic system, and the endocrine system--are all, in some way, linked to depression. This section has more on depression and:
Neurotransmitters Neurotransmitters are chemicals that circulate throughout the brain, carrying messages among the brain's nerve cells, or neurons. These neurons are responsible for everything our brains and bodies do. When we think, eat, want, run, read, even feel happy or sad, some of the billions of neurons in our brains make the action or emotion occur by transmitting signals from one neuron to another. About 30 different neurotransmitters flow through our system, making the important journey across the synaptic gulf between cells to bind to receptors on adjacent cells. The three neurotransmitters most closely linked to mood and depression are dopamine, norepinephrine, and serotonin. When the binding successfully occurs, emotions are regulated properly. When the binding doesn't work correctly, mood disorders can result. The limbic system The limbic system includes the hippocampus, the thalamus, the amygdala, and the hypothalamus, and is used to describe the part of the brain responsible for memory, emotions, mood, the experience of pleasure and pain, and the sense of smell, as well as various appetites. One part of the limbic system, the hypothalamus, regulates sleep, body temperature, sexual drive, and reactions to stress. When any part of this intricate system gets out of regulation, it affects the above functions, including moods. The endocrine system The endocrine system is a collection of glands that produce hormones throughout the body. Some hormones, like estrogen and testosterone, regulate the reproductive system, while others, like cortisol, mediate stress responses. When the body's level of a hormone is sufficient, the gland that produces it stops churning it out. The hormonal system that regulates the body's response to stress, the hypothalamic-pituitary-adrenal (HPA) axis, is overactive in many patients with depression. The hypothalamus, the brain region responsible for managing hormone release from glands throughout the body, increases production of a substance called corticotrophin-releasing factor (CRF) when a threat to physical or psychological well-being is detected. Elevated levels of CRF cause the pituitary and adrenal glands to increase the secretion of hormones that prepare the body for defensive action. The body's responses include reduced appetite, decreased sex drive, and heightened alertness. Persistent overactivation of this hormonal system may lay the groundwork for depression. Then when menopause, a medical illness like a thyroid condition or diabetes, or an unusual stress causes other hormones to fall out of balance, depression can result. At the same time, a depressive disorder can trigger the secretion of hormones that can then exacerbate other medical illnesses. Causes There is no single cause for depression. But its roots are generally found in the following:
Genes and depression Clearly, depressive illnesses run in families. But researchers have not yet located a single, defective gene responsible for the condition. Still, a host of studies have revealed that multiple gene variants, acting in concert with environmental stresses, can trigger psychiatric disorders. So while depressed parents don't pass on depression per se to children, the way they pass on hair or eye color, they can pass on a vulnerability to depression. Indeed, a depressed parent or sibling increases one's risk of developing the condition threefold. Studies of identical twins have been especially revealing. Researchers studying identical twins (who possess the same genetic code) have found that when one twin becomes depressed, the other twin also develops depression in 76 percent of cases. It would be easy to argue that this happens simply because they have shared the same early childhood experiences and, often, similar life stressors, too. But even when identical twins are raised apart, they will both become depressed 67 percent of the time. Fraternal twins have a much lower incidence of this kind of shared depression--only 19 percent of those whose twin is depressed will develop depression. Bipolar disorder has an even stronger genetic trail. When one parent has bipolar disorder, there is a significant chance that the child will develop some kind of clinical depression. When both parents have the disorder, the likelihood of passing it on to the children is even higher. Studies of families in which members of each generation develop bipolar disorder found that those individuals who develop the illness have a somewhat different genetic makeup from those who do not. However, it is important to note that not everyone with the genetic makeup that causes vulnerability to bipolar disorder will develop the illness. Additional factors, possibly stresses at home, work, or school, can act as triggers. Environment and depression Stressful occurrences in one's daily life--such as job pressures, divorce, illness, money problems, and deaths of close family members or friends--all are known risk factors for depression. Social isolation or emotional deprivation as a baby or young child may lead to permanent changes in brain function that increase one's susceptibility to depression. When a person also has a family history of this illness, the likelihood of difficult life events triggering a depression is increased. Medical illness and depression Depression frequently co-occurs with a variety of other physical illnesses, including heart disease, stroke, cancer, and diabetes. Depression also can increase the risk for subsequent physical illness, disability, and premature death. Further, the illness can make individuals less likely to seek and follow through with treatment for other medical illnesses. The symptoms of depression can also be caused by undiagnosed medical conditions, including epilepsy, multiple sclerosis, Huntington's disease, Parkinson's disease, hyperthyroidism, Lyme disease, and pancreatic cancer. When the medical illness is treated, the depression often lifts. This section has more on
Cancer Too often depression is seen as a "normal reaction" to a cancer diagnosis, which means that it doesn't require any special treatment. The prevalence of depression among cancer patients ranges from 23 percent to 60 percent. Obviously the life-changing nature of a cancer diagnosis has a great deal to do with this, but so do cytokines. Cytokines--such as interleukin--are secreted by the immune system to fight anything that can harm the body, including cancer or infections. Unfortunately, high levels of cytokines also result in a syndrome called "sickness behavior," characterized by a depressed mood, sleepiness, and poor concentration. In many patients, the emotional toll taken by a cancer diagnosis only intensifies this depressive syndrome. The challenge for physicians is to treat the depression while bolstering and sustaining the immunological response. Diabetes Many people who are depressed also have increased production of cortisol, the stress hormone. When cortisol is secreted, it leads to the release of amino acids, which are then turned into glucose, thereby raising blood sugar levels--which is a great problem for diabetics. Researchers have also found that patients with Type I diabetes have a hippocampus that is damaged, even atrophied, in a way that resembles those of people with depression. One possible explanation is that the brain structure changes caused by diabetes can also trigger depression. Another is that the brain structure changes caused by depression can exacerbate diabetes. Heart disease The link between depression and heart disease has been studied intensively. Many studies have demonstrated that when patients are depressed and have a heart attack or congestive heart failure, their outcomes tend to be poor compared with those of people who are not depressed. Indeed, depression appears to be an independent risk factor for the development of heart disease. Analysis of data from a large-scale survey revealed that individuals with a history of major depression were more than four times as likely to suffer a heart attack over a 12-to-13-year follow-up period as people without such a history. Even people with a history of 2 or more weeks of mild depression were more than twice as likely to have a heart attack, compared with those who had had no such episodes. Of course, depressed individuals are less likely to exercise, eat right, and take their medications. But the connection goes much deeper to the human stress response gone awry. When people are stressed, their blood-clotting system produces extra platelets, sticky cells that help slow down bleeding in the case of a wound. However, when the stress is emotional instead of physical, this response is maladaptive: Both heart attacks and strokes are caused by the formation of clots in the arteries. One study found that depressed patients exhibited increased platelet activation in comparison with normal subjects. Stress also activates cytokines, chemical messengers from the immune system, and elevated cytokine levels can trigger inflammation in the heart. Both depressed patients and cardiac patients lose flexibility in their heart muscles. A normal heart moves easily between its resting and beating states. But patients with severe coronary artery disease or with depression have more rigid hearts, less able to respond to the changing demands of the body for blood and oxygen. Osteoporosis Several studies have shown that an earlier history of depression is associated with marked osteoporosis, a disease in which bones become more porous and so more prone to breaking. Another study has found a link between reduced bone mineral density and depression. Risk factors Factors that may make you more prone to becoming depressed include:
Depression and gender Women experience depression about twice as often as men. Many hormonal factors may contribute to the increased rate of depression in women--particularly changes in hormone levels during the menstrual cycle, pregnancy, miscarriage, the postpartum period, peri-menopause, and menopause. Many women also face additional stresses, such as being the primary caretaker of children while working full time, single parenthood, or caring for children and for aging parents at the same time. The higher reported rate of depression among women might also stem from the fact that they tend to be more likely than men to talk about their unhappiness and seek treatment. Although men are less likely than women to suffer from depression, at least 6 million men in the United States suffer from a depressive disorder every year. But even though both men and women can develop the standard symptoms of depression, they often experience the illness differently and may have different ways of coping with the symptoms. Men are less likely to admit to feeling hopeless or sad. Instead, depression may show up as being irritable, angry, and discouraged. Further, men's depression is often masked by alcohol or drugs or by the socially acceptable habit of working excessively. Family history As much research has shown, depression can run in families. The connection stems not only from genes, however. When a family member has depression, spouses or siblings or children are inevitably affected emotionally by the illness, as well. Age Growing old is not easy: Friends and family members die. A satisfying professional life may be a thing of the past. Physical frailty usually may replace health, and the need for assistance with cooking, bathing, and dressing often replaces the ability to live independently. Still, depression should not be accepted as a normal part of aging. When left untreated, depression in the elderly causes needless suffering, both for individuals who could otherwise be leading a fruitful life and for family members whose emotional and financial resources may be depleted caring for those individuals. In the doctor's office, the older person may not discuss feelings of hopelessness or prolonged grief after a loss. But there is no stronger evidence of the problem of depression in older adults than the suicide rate. Suicide is often seen as a young man's act of desperation. But in fact, the elderly, particularly older white males, have the highest rates. Most older suicide victims have been to see their primary care physicians within the month of their death, many with a depressive illness that was not diagnosed, let alone treated. Medical illness and depression Many medical illnesses can trigger depression, and depressed people can be predisposed to developing some medical illnesses. When a person is diagnosed with a medical illness, managing the illness itself should often include treatment for depression. Our section on the causes of depression includes more on the relationship between depression and some medical illnesses. Pregnancy Hormonal and physical changes, loss of sleep, and responsibility for a new life can lead to postpartum depression in some women. While "post-baby blues" are common in new mothers, a full-blown depressive episode is not a normal occurrence and requires active intervention. Treatment by a sympathetic physician and support from family and friends can go a long way in helping new mothers recover their mental well-being. Seasonal affective disorder For some people, depression lifts when the spring and summer days are long and sunny, and descends during the darkness and gloom of late autumn and winter. Known as seasonal affective disorder (or SAD), this type of depression occurs more frequently in women than in men, but even children have suffered from it. While the precise cause of SAD is still being studied, researchers have found that the production of the neurotransmitter serotonin in the brain is directly related to the amount of time one is exposed to bright sunlight. Stress The stresses of divorce, unemployment, the illness of a close family member or friend, or even moving to a new city or getting married can trigger depression in people who are predisposed to the illness. Moreover, even if no stress caused the initial depression, subsequent stressors can deepen depression or prompt a second episode. One theory about how this happens is known as the "kindling/sensitization hypothesis." As the small flames in kindling can become a consuming forest fire, so too can the tougher stresses of normal life provoke a depressive episode in someone who is predisposed to the illness. Substance abuse Do people become substance abusers to ease symptoms of an underlying depression, or can excessive use of drugs or alcohol trigger depression? The answer appears to be both. Many people who are depressed but don't realize it "self-medicate" with drugs or alcohol. But this can have dire consequences in terms of addiction, as well as a more intractable depression when the initial euphoria from a drug- or alcohol-induced high triggers chemical reactions in the brain that lead to even deeper depression. Depression in children In the past, it was thought that depression simply was not a part of childhood. But over the past two decades, depression in children has become recognized as a serious medical problem that, if left untreated, can result in substance abuse, problems at school and relating to friends and family, and even suicide. Research has revealed that depression is occurring earlier in life today than in past decades. Early-onset depression often persists, recurs, and continues into adulthood. Depression in young people frequently occurs with other disorders like anxiety, attention deficit disorder, disruptive behaviors, substance abuse, and medical illnesses, including diabetes. A younger child who is depressed may pretend to be sick, refuse to go to school, cling to a parent, or be fixated on the fear that a parent may die. Older children may sulk, get into trouble at school, be negative and grouchy, and feel misunderstood. Childhood depression is sometimes missed because the above behaviors are viewed as normal at various childhood stages, so it can be difficult to tell whether a child is just going through a temporary "phase" or is suffering from true depression. Suicide When left untreated, severe depression can result in a suicide attempt, which in 30,535 cases each year is, tragically, successful. About 15 percent of those who are clinically depressed will die by suicide. The highest rate of suicide is among white men who are over the age of 85. But teenagers and adults in their early 20s are at the highest risk for suicide since so many contemplate and even attempt it, though far fewer successfully complete the act. Each year, about 20 percent of adolescents contemplate suicide; by the end of high school, 1 in 10 will have attempted it, with almost 2,000 succeeding each year. About half of those who die suffer from major clinical depression. In both depression and suicide, levels of a key neurochemical called serotonin are abnormally low. Advocates for the use of antidepressants point out that the teen suicide rate increased from 5.9 to 11.1 per 100,000 between 1970 and 1994 but declined to 7.4 per 100,000 in 2002, just when the drugs were increasingly being prescribed for children.Modern antidepressants that boost serotonin levels are also credited with the small but real decline in the overall suicide rates internationally. But occasionally these drugs energize a depressed person before actually lifting the depression. Thus, in those rare cases, the risk of suicide can increase after a person begins taking medications. In addition, the Food and Drug Administration has cautioned that some of these drugs, when used in those under 18, might increase suicidal behavior. A universal and perplexing reality is suicide's maleness. More than four times as many men as women die by suicide (although more women report making the attempt). Boys kill themselves six times as often as girls do. In 2000, the United States had 4,294 recorded suicides in the 10-to-24-year-old age group; only 632 of them were girls--this despite the fact that females are diagnosed with depression more often and make many more suicide attempts. A closer look suggests that males often experience and express their illness differently--more aggression, anger, irritability, and impulsiveness and less of the overt hopelessness, helplessness, and sadness common in suicidal females. These numbers reveal not only the scope of the problem but also the vast difference between the state of contemplating suicide--also called suicidal ideation--a suicide attempt, and an actual suicide. Ideation, it seems, is part of adolescence for 1 in every 5 kids in a high school classroom. A suicide attempt, however, becomes murkier in terms of reporting: Is cutting oneself on the wrist, say, a suicide attempt or a way of relieving tension? Of course, it depends on the patient. If someone is cutting herself, this self-mutilation is often serious and scarring, according to psychiatrists, but still is not attempted suicide. Researchers have found that those who cut themselves have no wish to die, no matter how difficult that may be to understand. They find that cutting relieves unbearable anxiety, somehow, or channels anger. What is most important, however, is the link between depression and suicide. The suicide prevention programs that are the most likely to succeed are those that focus on the identification and treatment of depression and substance abuse and that teach people how to cope with stress and manage their aggressive behaviors and feelings. |
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