depression
What are common symptoms of depression?
How does depression differ from grief or mourning?
What are some causes of depression?
What are the main treatments for depression?
What types of depression exist?
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depression, in psychology, a mood or emotional state that is marked by feelings of low self-worth or guilt and a reduced ability to enjoy life. A person who is depressed usually experiences several of the following symptoms: feelings of sadness, hopelessness, or pessimism; lowered self-esteem and heightened self-depreciation; a decrease or loss of ability to take pleasure in ordinary activities; reduced energy and vitality; slowness of thought or action; loss of appetite; and disturbed sleep or insomnia.
If you are experiencing a crisis or would like to speak with someone about depression, call the National Suicide and Crisis Lifeline at 988 or contact the Crisis Text Line by texting HOME to 741741.
Depression differs from simple grief or mourning, which are appropriate emotional responses to the loss of loved persons or objects. Where there are clear grounds for a person’s unhappiness, depression is considered to be present if the depressed mood is disproportionately long or severe vis-à-vis the precipitating event. The distinctions between the duration of depression, the circumstances under which it arises, and certain other characteristics underlie the classification of depression into different types. Examples of different types of depression include major depressive disorder (clinical depression), persistent depressive disorder, perinatal (postpartum) depression, and seasonal affective disorder.
Characteristics and causes of depression
Depression is one of the most common mental health disorders and has been described by physicians since before the time of ancient Greek physician Hippocrates, who called it melancholia. The course of the disorder is extremely variable from person to person; it may be mild or severe, acute or chronic. Untreated, depression may last an average of several months or longer. Depression is diagnosed about twice as often in women as in men, though the disorder affects people of all sexes and genders. The typical age of onset is in the 20s, but it may occur at any age.
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Depression can have many causes. Stressful or unfavorable life events can increase a person’s vulnerability to depression or trigger a depressive episode. Negative thoughts about oneself and the world can also contribute to the development and persistence of depressive symptoms. However, both psychosocial and biochemical mechanisms are thought to play important roles. Research suggests that depression involves complex interactions among neurotransmitters, neural circuits, genetic factors, hormones, immune-system activity, and environmental influences. In particular, neurotransmitters such as norepinephrine, serotonin, and dopamine, are suspected to be involved in mood regulation, though depression cannot be explained solely by deficiencies in these chemicals.
Depression is also associated with disordered rapid eye movement (REM) sleep. A region of the brain known as the amygdala contains neurons that project into the brainstem and may help regulate REM sleep. The amygdala is also involved in emotional processing and has been found in some studies to show altered activity or structure in depressed individuals. Although the significance of these findings remains under investigation, the links between depression, sleep disturbances, and brain function have contributed to ongoing research into the neurobiology and treatment of depressive disorders.
Research further suggests that depression is linked to physical activity, with regular exercise potentially lowering a person’s risk of developing depression and helping reduce symptoms in some individuals. People who exercise regularly often report better mental health and lower rates of depression than those who are physically inactive.
Types of depression
Major depressive disorder and persistent depressive disorder are among the primary types of depression. Major depressive disorder is characterized by severe symptoms that disrupt the individual’s daily life, typically with effects on appetite, sleep, work, or the ability to enjoy life. Episodes of major depression can occur at any age and may occur once or multiple times in an affected person’s life. Persistent depressive disorder involves symptoms that last two or more years, sometimes marked by episodes of major depression. Bipolar disorder is a related mood disorder characterized by episodes of depression alternating with periods of mania (abnormally elevated mood, energy, or activity) or hypomania (a less severe form of mania).
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Other types of depression include perinatal depression, psychotic depression, and seasonal affective disorder, each of which develops under specific circumstances. Perinatal depression can occur during pregnancy or after childbirth. Symptoms include anxiety, a lack of interest in caring for the infant, and feelings of sadness, hopelessness, or inadequacy. Postpartum depression is longer-lasting and more severe than the “baby blues,” a common condition among women after childbirth that typically involves mood swings, feelings of sadness, and crying spells. Psychotic depression (major depression with psychotic features) involves severe depressive symptoms accompanied by psychosis, which may include delusions, hallucinations, or paranoia. Seasonal affective disorder is characterized by the onset of depressive symptoms in autumn and winter, which are alleviated with increased exposure to natural light in spring and summer.
Treatments for depression
There are several effective treatments for depression. The two most widely used are psychotherapy and psychotropic medication, specifically antidepressants such as bupropion and selective serotonin reuptake inhibitors (SSRIs). Psychotherapy aims to alter the patient’s maladaptive cognitive and behavioral responses to stressful life events while also giving emotional support to the patient. Antidepressant medications affect brain systems involved in mood regulation; their therapeutic effects involve complex changes in neurotransmitter signaling, neural circuits, and neuroplasticity.
Two major classes of medications are SSRIs (such as fluoxetine, also known as Prozac) and serotonin-norepinephrine reuptake inhibitors (SNRIs), which increase the availability of neurotransmitters involved in mood regulation. Older classes of antidepressants, including tricyclic antidepressants and monoamine oxidase inhibitors (MAOIs), are also effective but are generally used less frequently because of their side-effect profiles and dietary or medication interactions.
In cases of severe depression in which therapeutic results are needed quickly, electroconvulsive therapy (ECT) has sometimes proved helpful. In this procedure, a convulsion is produced by passing an electric current through the person’s brain. For most persons with depression, however, the best therapeutic results are obtained by using a combination of psychotherapy and antidepressant medication.
Some individuals experience treatment-resistant depression (TRD), meaning that their symptoms do not respond adequately to standard therapies. For those individuals, scientists have been investigating alternative approaches, including deep brain stimulation (DBS), transcranial magnetic stimulation (TMS), ketamine and esketamine therapies, and other neuromodulation techniques. In DBS, experimental research has focused on the implantation of an electrode in a region of the brain known as the nucleus accumbens to alter neural activity. Although DBS has shown promise in some studies, it remains experimental for depression and is associated with potential risks. Research into the biological mechanisms of depression, including the role of proteins such as p11, continues to inform the development of new treatments.