People with depressive illnesses do not all experience the same symptoms.
The severity, frequency, and duration of symptoms vary depending on the individual and his or her particular illness.
Brain-imaging technologies, such as magnetic resonance imaging (MRI), have shown that the brains of people who have depression look different than those of people without depression. The parts of the brain involved in mood, thinking, sleep, appetite, and behavior appear different. But these images do not reveal why the depression has occurred. They also cannot be used to diagnose depression.
Some types of depression tend to run in families. However, depression can occur in people without family histories of depression too. Scientists are studying certain genes that may make some people more prone to depression. Some genetics research indicates that risk for depression results from the influence of several genes acting together with environmental or other factors.
In addition, trauma, loss of a loved one, a difficult relationship, or any stressful situation may trigger a depressive episode. Other depressive episodes may occur with or without an obvious trigger.
Research indicates that depressive illnesses are disorders of the brain.1
Many social indicators fail to measure what people think and feel about their lives—the quality of their relationships, their positive emotions, resilience, satisfaction with life domains, or the realization of their potential. Positive evaluations of life including the presence of positive emotions (e.g., happiness, serenity, interest), social ties, and perceptions of life satisfaction and meaning, are commonly referred to as “well-being.”
To learn more about how well-being can be useful to public health, how it is measured, and what Centers for Disease Control and Prevention is doing to examine and promote well-being, please visit Health Related Quality of Life.22