National Alliance on Mental Illness
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Symptoms, Causes and Diagnosis
Depression can be difficult to detect from the outside looking in, but for those who experience major depression, it is disruptive in a multitude of ways. The symptoms of clinical depression usually represent a significant change in how a person functions. The following are key areas where depression causes major changes in people.
The general scientific understanding is that depression does not have a single cause; it arises from multiple factors that may need to occur simultaneously. A person’s life experience, genetic inheritance, age, sex, brain chemistry imbalance, hormone changes, substance abuse and other illnesses all play significant roles in the development of a depression. It also may be that there is no observable trigger leading to the illness; depression may occur spontaneously and be unassociated with any life crisis, physical illness or other currently known risks.
The occurrence of mood disorders and suicides tend to run in families. We know that a biologically inherited tendency to develop depression is associated with a younger age of depression onset, and that new onset depression occurring after age 60 is less likely due to genetic predisposition. Life factors seem to influence whether an inherited, genetic tendency will ever lead to an episode of major depression.
Certain aspects of life, such as marital status, financial standing and where a person lives, do have some bearing on whether someone develops depression, but it can be a case of “the chicken of the egg.” For instance, though depression is more common among people who are homeless, it may be that depression strongly influences why any given person becomes homeless. We also know that long-lasting stressors like unemployment or a difficult marriage play a more significant role in developing depression than sudden stressors like an argument or receiving bad news.
Traumatic experiences may not only contribute to one’s general state of stress, but also seem to alter how the brain functions for years to come. Early-life traumatic experiences have been shown to cause long-term changes in how the brain responds to future fears and stresses. This may be what accounts for the greater lifetime incidence of major depression in people who have a history of significant childhood trauma.
Other proposed genetic pathways in the development of depression include changes observed in the regional brain functioning. For instance, imaging studies have shown consistently that the left, front portion of the brain becomes less active during depression. Also, brain patters during sleep change in a characteristic way. Depression is also associated with changes in how the pituitary gland and hypothalamus respond to hormone stimulation.
Other factors that have been linked to depression include a history of sleep disturbances, medical illness, chronic pain, anxiety, attention-deficit hyperactivity disorder, alcoholism or drug abuse. Our current understanding is that major depression can have many causes and develop from a variety of genetic pathways.
The American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) is the current reference used by health care professionals to diagnose metnal illnesses such as depression. This manual was first published in 1952 and has since gone through several revisions. The current edition was published in 1994 and lists over 200 mental health conditions and the criteria required for each one in making an appropriate diagnosis. the DSM-V is scheduled to be published in 2013
In the DSM-IV, depression is classified as a mood disorder. the DSM-IV's criteria for a major depressive episode (which needs to last longer than two weeks) include:
There is a strong possibility that a depressive episode can be a part of bipolar disorder. Having a physician make the right distinction between unipolar and bipolar disorder is critical because treatments for these two depressive disorders differ. The use of antidepressants, (the cornerstone of treatment of major depression) can sometimes activate manic symptoms or even worsen depressive symptoms, including suicidal thinking, in people with bipolar depression. At the same time, antidepressants do not appear to be particularly effective for treating bipolar depression. In major depression associated with bipolar disorder, mood stabilizers and psychosocial treatments-not antidepressants-have a strong evidence base and can often be effective. Speaking with a mental health care provider can help guide this process.