When discussing depression as a symptom, a feeling of hopelessness is the most often described sensation. Depression is a common psychiatric disorder in the modern world and a growing cause of concern for health agencies worldwide due to the high social and economic costs involved. Symptoms of depression, like the disorder itself, vary in degree of severity, and contribute to mild to severe mood disturbances. Mood disturbances may range from a sudden transitory decrease in motivation and concentration to gloomy moods and irritation, or to severe, chronic prostration.
With treatment, more than 80% of people with depression respond favorably to medications, and the feeling of hopelessness subsides. With treatment, most people are able to resume their normal work and social activities.
Depression may occur at almost any stage of life, from childhood to middle or old age, as a result of a number of different factors that lead to chemical changes in the brain. Traumatic experiences, chronic stress, emotional loss, dysfunctional interpersonal relationships, social isolation, biological changes, aging, and inherited predisposition are common triggers for the symptoms of depression. Depression is classified according to the symptoms displayed and patterns of occurrence. Types of depression include major depressive disorder, bipolar depressive disorder, psychotic depressive disorder, postpartum depression, premenstrual dysphoric disorder, and seasonal disorder. Additional types of depression are included under the label of atypical depressive disorder. Many symptoms overlap among the types of depression, and not all people with depression experience all the symptoms associated with their particular type of the disorder.
Symptoms of a depressive disorder include at least five of the following changes in the individual’s previous characteristics: loss of motivation and inability to feel pleasure; deep chronic sadness or distress; changes in sleep patterns; lack of physical energy (apathy); feelings of hopelessness and worthlessness; difficulty with concentration; overeating or loss of appetite; withdrawal from interpersonal interactions or avoidance of others; death wishes, or belief in his/her own premature death. In children, the first signs of depression may be irritation and loss of concentration, apathy and distractibility during classes, and social withdrawal. Some adults initially complain of constant fatigue, even after long hours of sleep, digestive disorders, headaches, anxiety, recurrent memory lapses, and insomnia or excessive sleeping. An episode of maression may be preceded by a period of dysthymia, a mild but persistent low mood state, usually accompanied by diminished sexual drive, decreased affective response, and loss of interest in normal social activities and hobbies.
Most individuals with depression have difficulty in dealing with the challenges of daily life, and even minor obstacles or difficulties may trigger exaggerated emotional responses. Frustrating situations are frequently met with feelings of despair, dejection, resentment, and worthlessness, with people easily desisting from their goals. People with depression may try to avoid social situations and interpersonal interactions. Some people with depression overeat, while others show a sharp loss of appetite (anorexia). In some individuals, medical treatments for some other existing illness may also cause depression as an adverse reaction. For instance, antihypertensive drugs, steroids, muscle relaxants, anticancer drugs, and opioids, as well as extensive surgery such as a coronary bypass, may lead to depression. Cancer and other degenerative diseases, chronic painful conditions, metabolic diseases or hormonal changes during adolescence, or after childbirth, menopause, or old age may be potential triggers for depression. When the first onset of depression occurs after the age of 60, there is a greater possibility that the causative factor is a cerebrovascular (blood vessels in the brain) degeneration.
Molecular genetics research has recently shown that mutations in a gene coding for a protein that transports serotonin (a neurotransmitter) to neurons may determine how an individual will cope with stressful situations. A two-decade study involving 847 people of both sexes has shown that those who inherited two copies of the long version of the gene 5-HTT have a 17% risk of suffering a major depressive episode due to exposure to four or more identified stressful situations in their lives, whereas those with one long and one short version of the gene had the risk increased to 33%. The study has also shown that individuals with two short copies of the gene have a 43% probability of a major depressive episode when exposed to four or more stressful life events. The shorter version of the gene 5-HTT does not directly causes depression, but offers less protection against the harmful effects of traumatic or stressful situations to the brain. Studies of population genetics have also shown that about 50% of the world’s Caucasian population carry one short and one long version of 5-HTT genes.
Depressive episodes may be associated with additional psychiatric disorders. Neurotic depression is often triggered by one or more adverse life events or traumatic experiences that have historically caused anxiety in the life of the person experiencing depression. For example, loss of social or economical status, chronic failure in living up to the expectations of parents, teachers, or bosses, death of a close relation, work-related competitive pressures, and other stressful situations such as accidents, urban violence, wars, and catastrophic events may lead to a depressive episode. Conversely, anxiety disorders such as panic syndrome, phobias, generalized anxiety, and post-traumatic stress disorder may trigger a major depressive crisis. Psychotic depressive disorders are likely to be associated with other psychiatric diseases or caused by them. Eating disorders such as bulimia, anorexia nervosa, and binge-eating disorder are generally accompanied by depression or may be caused by an existing depressive state. Neurodegenerative diseases such as Alzheimer’s, Huntington’s, and Parkinson’s diseases frequently have depression among their symptoms.
Dysthymia is a mild but chronic depressed state, characterized by melancholic moods, low motivation, poor affective responsiveness, and a tendency for self isolation. A dysthymic state lasting two years or longer is a risk factor for the onset of a major depressive episode. However, many dysthymic individuals experience a chronic low mood state throughout their daily lives. Dysthymia is a frequent occurrence in individuals involved in chronic dysfunctional marriages or unsatisfying work conditions. Such chronic stressful situations alter the brain’s neurochemistry, thus the opportunity arises for symptoms of depression to develop.
Psychotic depression is a particularly serious illness and possesses biological and cognitive (thought) components. Psychotic depression involves disturbances in brain neurochemistry as a consequence of either a congenital (from birth) condition or due to prolonged exposure to stress or abuse during early childhood. Prolonged exposure to severe stress or abuse in the first decade of life induces both neurochemical and structural permanent changes in the developing brain with a direct impact on emotional aspects of personality. Normal patterns of perception and reaction give way to flawed mechanisms in order for a person to cope with chronic fear, abuse, and danger. Perception becomes fear-oriented and conditioned to constantly scan the environment for danger, with the flight-or-fight impulse underlying the individual’s reactions. Delusions, misinterpretation of interpersonal signals, and a pervading feeling of worthlessness may impair the individual’s ability to deal with even minor frustrations or obstacles, precipitating deep and prolonged episodes of depression, often with a high risk of suicide. Hallucinations may also occur, such as hearing voices or experiencing visions, as part of depression with psychosis.
A major depressive disorder (MDD) or clinical depression may consist of a single episode of severe depression requiring treatment or constitute the initial sign of a more complex disorder such as bipolar disorder. MDD may last for several months or even years if untreated and is associated with a high risk of suicide. In bipolar disorder, manic (hyper-excited and busy) periods alternate with deep depressive episodes, and are characterized by abnormal euphoria (an exaggerated feeling of happiness and well-being) and reckless behavior, followed by deep distress and prostration, often requiring hospitalization.
Major episodes of depression may last for one or more years if not treated, leading to a deep physical and emotional prostration. The person with major depression often moves very slowly and reports a sensation of heaviness in the arms and legs, with simple walking requiring an overwhelming effort. Personal hygiene is neglected and the person often desires to stay secluded or in bed for days or weeks. Suicidal thoughts may frequently occupy the mind or become recurrent patterns of thinking. Painful or unsettling memories are often recalled, and contribute to feelings of helplessness.
Atypical depression causes a cyclic behavior, alternating periods of severe and mild depressive states, punctuated by mood swings, hypersensitivity, oversleeping, overeating, with or without intermittent panic attacks. This depressive disorder is more common in women, with the onset usually occurring during adolescence.
Premenstrual dysphoric disorder (PDD) is not premenstrual stress. It is a more severe mood disorder that can cause deep depression or episodes of heightened irritation and aggressiveness, starting one or two weeks before menstruation and usually persisting during the entire period. Premenstrual dysphoric disorder is associated with abnormal changes in levels of hormones that affect brain neurochemistry.
Seasonal affective disorder (SAD) is caused by disturbances in the circadian cycle, a mechanism that controls conversion of serotonin into melatonin in the evening and mid-afternoon, and the conversion of melatonin into serotonin during daytime. Serotonin is the neurotransmitter responsible for sensations of satiety and emotional stability, which is converted at nighttime into melatonin, the hormone that regulates sleep and other functions. Some people are especially susceptible to the decreased exposure to daylight during long winter months and become depressed and irritable. Overeating and oversleeping during the winter season are common signs of seasonal affective disorder, along with irritation and depressed moods. However, as the amount of light increases during the spring and summer seasons, the symptoms disappear.
Postpartum depression is a severe and long-lasting depressive state also associated with abnormal changesmone levels affecting brain neurochemistry. If untreated, postpartum depression may last for months or even years, and is highly disruptive to family and maternal-child relations.
Without treatment, the risk of suicide as a consequence of depression should not be underestimated. Suicide accounts for approximately 15% of deaths among people with significant depression, and half of all suicide attempts in the United States are associated with depression. Persistent and recurrent depressive episodes are important contributors to other diseases alike such as myocardial infarction, hypertension, and other cardiovascular disorders.
Klein, Donald F., MD. Understanding Depression: A Complete Guide to Its Diagnosis and Treatment. New York: Oxford Press, 1995.
Solomon, Andrew. The Noonday Demon: An Atlas of Depression. New York: Scribners, 2002.
Manji, H. K., W. C. Drevets, and D. S. Charney. “The Cellular Neurobiology of Depression.” Nature Medicine (May 2001) 7: 541–546.
Teicher, Martin H. “Wounds That Won’t Heal–The Neurobiology of Child Abuse.” Scientific American (March 2002): 68–75.
National Institute of Mental Health: Depression. February 12, 2004 (March 31, 2004).
National Institute of Mental Health (NIMH). Office of Communications, 6001 Executive Boulevard, Room 8184, MSC 9663, Bethesda, MD 20892-9663. (301) 443-4513 or (800) 615-NIMH (6464); Fax: (301) 443-4279. firstname.lastname@example.org.