Depression is a state of low mood and aversion to activity that can affect a person's thoughts, behavior, feelings and physical well-being. It may include feelings of sadness, anxiety, emptiness, hopelessness, worthlessness, guilt, irritability, or restlessness.
Depressed people may lose interest in activities that once were pleasurable, or suffer cognitive impairments (e.g., difficulty concentrating, remembering details, making decisions). They may contemplate or attempt suicide. Their weight may change dramatically. Insomnia, excessive sleeping, change in sleep patterns (e.g., waking in the middle of the night or early in the morning and being unable to fall asleep again), fatigue, loss of energy, and aches, pains or digestive problems that are resistant to treatment may be present.
Depressed mood is a normal reaction to certain life events, a symptom of many medical conditions (e.g., Addison's disease, hypothyroidism), and a feature of certain psychiatric syndromes.
A number of psychiatric syndromes feature depressed mood as a main symptom. Mood disorders are a group of disorders considered to be primary disturbances of mood. Within them, major depressive disorder (MDD), commonly called "major depression" or "clinical depression", is a condition where a person has at least two weeks of depressed mood or a loss of interest or pleasure in nearly all daily activities. People suffering bipolar disorder may also experience major depressive episodes. Dysthymia is a state of chronic depressed mood, the symptoms of which do not meet the severity of a major depressive episode. Outside the mood disorders, moderate chronic depressed mood is also commonly a feature of borderline personality disorder. Adjustment disorder with depressed mood is a mood disturbance appearing as a psychological response to an identifiable event or stressor, in which the resulting emotional or behavioral symptoms are significant but do not meet the criteria for a major depressive episode.
Depressed mood can be the result of a number of infectious diseases and physiological problems. For example, mononucleosis (glandular fever), which can be caused by two different viral infections, often results in symptoms that mimic a depressive psychiatric disorder; and depression is often one of the early symptoms of hypothyroidism (reduced activity of the thyroid gland). For a discussion of non-psychiatric medical illnesses that can cause depressed mood, see Depression (differential diagnoses).
Depression from life events can cause a dangerous feedback loop, and thus a self-fulfilling prophecy, where sad memories come to mind and cause deeper depression, all the while hurting the patient's abilities to problem solve and take initiative. A depressive mood from life events is a main focus of the field of positive psychology.
A 2010 Centers for Disease Control and Prevention survey investigated current depression in the United States during 2006 and 2008. Current depression was defined as either major depression or "other depression" during the 2 weeks preceding the survey. Among 235,067 adults (in 45 states, the District of Columbia [DC], Puerto Rico, and the U.S. Virgin Islands), 9.0% met the criteria for current depression, including 3.4% who met the criteria for major depression. By state, age-standardized estimates for current depression ranged from 4.8% in North Dakota to 14.8% in Mississippi.
A full patient medical history, physical assessment, and thorough evaluation of symptoms helps determine the cause of the depression. Standardized questionnaires can be helpful such as the Hamilton Rating Scale for Depression, and the Beck Depression Inventory.
A doctor generally performs a medical examination and selected investigations to rule out other causes of symptoms. These include blood tests measuring TSH and thyroxine to exclude hypothyroidism; basic electrolytes and serum calcium to rule out a metabolic disturbance; and a full blood count including ESR to rule out a systemic infection or chronic disease. Adverse affective reactions to medications or alcohol misuse are often ruled out, as well. Testosterone levels may be evaluated to diagnose hypogonadism, a cause of depression in men.
Subjective cognitive complaints appear in depressed people, but they can also be indicative of the onset of a dementing disorder, such as Alzheimer's disease. Cognitive testing and brain imaging can help distinguish depression from dementia. A CT scan can exclude brain pathology in those with psychotic, rapid-onset or otherwise unusual symptoms. Investigations are not generally repeated for a subsequent episode unless there is a medical indication.
What will work to treat a person's depression depends on the cause. This means there are a wide variety of possible solutions, and it can be exceptionally difficult for doctors, psychiatrists and psychologists to know which one is needed. All of this is only harder for non-professionals, and so depressed individuals are advised to talk to professionals.
Although depression is a highly treatable condition, some forms of depression may not be preventable. That's because depression may be triggered by a chemical malfunctioning in the brain. However, the latest medical studies confirm that depression may often be alleviated or sometimes prevented with good health habits.
Proper diet, exercise, taking time out for fun and relaxation, not overworking, and saving time to do things you enjoy may work together to prevent a depressed mood.