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Depression (also known as unipolar depression or clinical depression) is a mood disorder which often involves a loss of interest in life, or "anhedonia".

It is common to feel sad, discouraged, or "down" once in a while, but for some people, this mood persists. When symptoms last two weeks or more, and are so severe that they interfere with daily living, one can be said to be suffering from depression.

Depression affects nearly 10% of the population at one time or another in their lives; it occurs most often between the ages of 24 and 44. About twice as many women as men report or receive treatment for depression, though the gap is shrinking.

Causes of depression

No specific cause for depression has been identified, but there are a number of factors believed to be involved.

  • Heredity The tendency to develop depression may be inherited; there is some evidence that this disorder may run in families.
  • Brain chemicals called neurotransmitters allow electrical signals to move from the axon of one nerve cell to the neuron of another.
  • A shortage of neurotransmitters impairs brain communication.

Physiology: There may be changes or imbalances in certain chemicals the brain uses to transmit information. These neurotransmitters include chemicals such as serotonin, and many modern antidepressants work on the assumption that an imbalance in this chemical is a factor in depression. While it is not clear which is the cause and which is the effect, it is known that antidepressant medications do help alleviate the symptoms of depression. Seasonal affective disorder (SAD) is a type of depressive disorder that occurs in the winter when daylight hours are short. It is believed that the body's production of melatonin, which is produced at increased levels in the dark, plays a major part in the onset of SAD, and that many sufferers respond well to bright light therapy, also known as phototherapy.

  • Psychological factors Low self-esteem and self-defeating or distorted thinking are connected with depression. While it is not clear which is the cause and which is the effect, it is known that sufferers who are able to make corrections to their thinking patterns can show improved mood and self-esteem. Psychological factors include the complex development of one's personality and how one has learned to cope with external environmental factors, such as stress.
    Early experiences Events such as the death of a parent, abandonment or rejection, neglect, chronic illness, and severe physical, psychological, or sexual abuse can also increase the likelihood of depression later in life. Post-traumatic stress disorder (PTSD) includes depression as one of its major symptoms.
  • Life experiences Job loss, financial difficulties, long periods of unemployment, the loss of a spouse or other family member, or other traumatic events may trigger depression.
    Medical conditions Certain illnesses including hepatitis or mononucleosis may contribute to depression, as may certain prescription drugs such as birth control pills and steroids.
  • Alcohol and other drugs Alcohol can have a negative effect on mood, and misuse or abuse of alcohol, benzodiazepine-based tranquillizers and sleeping medications, or narcotics can all play a major role in the length and severity of depression.
  • Post-partum depression About ten percent of new mothers experience some form of depression after childbirth. When it occurs, the onset is typically within three months after delivery, and it may last for several months. About two new mothers out of a thousand have depression so severe it includes hallucinations or delusions.
  • Living with a depressed person Those living with someone suffering from depression experience increased stress, anxiety, and life disruption, which increases the possibility of their also becoming depressed.
  • BioMechanical-Neurological Excessive stimulation of the neuroloigical system may lead to clinical depression. The degree and persistence of the depression is directly related to the degree and persistence of the stimulation. This neurological reflex is part of the bodies natural defenses,that have evolved through evolution,to protect itself from harm. Over work,physically or mentally, may over stimulate the neurological system which reflexively responds by creating a sense of tiredness mentally and physically-the desire to do anything is much reduced.

Signs and symptoms

According to the DSM-IV-TR (p. 356), the two principal or required elements of depression are:

  • depressed mood, or
  • loss of interest or pleasure.

It is sufficient to have either of these symptoms in conjunction with four of a list of other symptoms. The diagnosis does not require "loss of interest in life, anhedonia". Likewise, "lack of energy and motivation" is not at all a required symptom of major depression.

In adults, symptoms accompanying depression often include:

  • feelings of overwhelming sadness, or complete lack of emotion
  • marked decrease in interest in pleasurable activities
  • changing appetite and marked weight gain or weight loss
  • disturbed sleep patterns, either insomnia or sleeping more than normal
  • changes in activity levels, restless or moving significantly slower than normal
  • fatigue, both mental and physical
  • feelings of guilt, helplessness, anxiety, and/or fear
  • lowered self-esteem
  • decreased ability to concentrate or make decisions
  • thinking about death or suicide
  • drug or alcohol use.

Depression in children is not as evident as it is in adults; symptoms children demonstrate include

  • loss of appetite
  • sleep problems such as nightmares
  • problems with behavior or grades at school where none existed before
  • significant behavioral changes; becoming withdrawn, sulky, aggressive
  • In older children and adolescents, an additional indicator may be the use of drugs or alcohol.

Most people who have not experienced clinical depression do not properly understand its emotional impact, interpreting it instead as being similar to "having the blues" or "feeling down". As the list of symptoms above indicates, clinical depression is a syndrome of interlocking symptoms which goes far beyond sad or painful feelings. A variety of biological indicators, including measurement of neurotransmitter levels, have shown that there are significant changes in brain chemistry and an overall reduction in brain activity. One consequence of a lack of understanding of its nature is that depressed individuals are often criticized by themselves and others for not making an effort to help themselves. However, the more severe the depression is, the more the depression may take on an autonomous nature, responding neither to positive events nor to the person's own efforts to feel better. Because of its intractable nature, it is imperative that the depressed individual seek professional help. Untreated depression is typically characterized by progressively worsening episodes separated by plateaus of temporary stability or remission, and often leads to suicide.

Types of major depression

Major depression is also referred to as major depressive disorder or biochemical, clinical, endogenous, or biological depression. It is characterized by a severely depressed mood that persists for at least two weeks. Episodes of depression may start suddenly or slowly and can occur several times though a person's life.


Clinicians recognise several subtypes of major depression.

  • Melancholia is very severe, and includes a number of major physical symptoms including sleep and appetite disturbances, weight loss, and withdrawal. The name derives from 'black bile', one of the imagined 'four humours' postulated by Hippocrates.
  • Psychotic depression is similar to melancholia, and is accompanied by hallucinations or delusions.
  • Atypical depression is characterized by anxiety and panic attacks.
  • Chronic dysthymic disorder is a long-term, mild depression that lasts for at least two years. It often begins in adolescence and spans several decades.

Major depression may also be referred to as unipolar affective disorder.

Bipolar disorder

Bipolar disorder, sometimes called manic depression, is a cyclical illness in which moods fluctuate between extreme happiness or giddiness and frantic activity (the manic stage) and profound depression.


Treatment of depression varies broadly, and is different for each individual. Various types and combinations of treatments may have to be tried. There are two primary modes of treatment, typically employed in conjunction with one another, medication and psychotherapy. A third treatment, electroconvulsive therapy (ECT) may be used where chemical treatment fails. Other alternative treatments used for depression include exercise, and the use of vitamins, herbs, or other nutritional supplements.

The effectiveness of treatment often depends on factors such as the amount of optimism and hope the sufferer is able to maintain, the control s/he has over stressors, the severity of symptoms, the amount of time the sufferer has been depressed, the results of previous treatments, and the degree of support of family, friends, and significant others.


Medication which effectively ameliorates the symptoms of depression has been available for several decades.

Tricyclic antidepressants are the oldest, and include such medications as amitryptyline and desipramine. They are used less commonly now, due to side-effects which may include increased heart rate, drowsiness, and memory impairment.

Monoamine oxidase inhibitors (MAOIs) may be used if other antidepressant medications are ineffective. Because there are undesirable interactions between this class of medication and certain foods and drugs, it is important that the user be aware of which ones to avoid. A new MAOI has recently been introduced. Moclobemide (Manerix), known as a reversible inhibitor of monoamine oxidase A (RIMA), follows a very specific chemical pathway and does not require a special diet.

Selective serotonin reuptake inhibitors (SSRIs) comprise the current standard family of antidepressants. It is thought that one cause of depression is that an inadequate amount of serotonin, a chemical which the brain uses to transmit signals between nerve cells, is produced. These drugs work by preventing the reabsorption of serotonin by the nerve cell, thus maintaining the levels the brain needs to function effectively. This family of drugs includes fluoxetine (Prozac), paroxetine (Paxil), and nefazodone (Serzone). These antidepressants typically have fewer adverse side effects than the tricyclics or the MAOIs, though such effects as drowsiness, dry mouth, and decreased ability to function sexually may occur.

Some antidepressants have been found to work more effectively in some patients when used in combination with another drug. Such "augmentor" drugs include tryptophan (Tryptan) and buspirone (Buspar).

Tranquillizers and sedatives, typically the benzodiazepines, may be prescribed to ease anxiety and promote sleep. Because of their high potential for addiction, these medications are intended only for short-term or occasional use. Medications are often employed not for their primary function, but to exploit what are normally side effects. Quetiapine fumarate (Seroquel) is designed primarily to treat schizophrenia and bipolar disorder, but a frequently-reported side-effect is somnolence. Hence, this non-addictive drug can be used in place of an addictive anti-anxiety agent such as clonazepam (Klonopin, Rivotril).

Antipsychotics such as risperidone (Risperdal) and olanzapine (Zyprexa) are prescribed as mood stabilizers and are also effective in treating anxiety. However, they may have serious side effects, particularly at high doses, which may include blurred vision, muscle spasms, restlessness, tardive dyskinesia, and weight gain.

Lithium remains the standard treatment for bipolar disorder, but may also be effective for people with depression, particularly in preventing relapse. Lithium's potential side effects include thirst, tremors, light-headedness, and nausea or diarrhea.

Failure to take medication, or failure to take it as prescribed, is one of the major causes of relapse. Should one feel a change or discontinuation of medication is necessary, it is critical that this be done in consultation with a doctor.


In psychotherapy, or counselling, one receives assistance in understanding and resolving problems which may be contributing to depression. This may be done individually or with a group, and is conducted by health professionals such as psychiatrists, psychologists, social workers, or psychiatric nurses. It is important to enquire about both the therapist's training and approach; a very close bond often forms between practitioner and client, and it is important that the client feel understood by the clinician.

Counsellors can help a person make changes in thinking patterns, deal with relationship issues, detect and deal with relapses, and understand the factors that contribute to depression.

There are many therapeutic approaches, but all are aimed at improving an individual's personal and interpersonal functioning. Cognitive therapy focuses on how people think about themselves and their relationship to the world. It works to counteract negative thought patterns and enhance self-esteem. Therapy can be used to help a person develop or improve interpersonal skills in order to allow them to communicate more effectively and reduce stress. Behavioral therapy is based on the assumption that behaviors are learned. This type of therapy attempts to teach individuals new and healthier types of behaviors. Supportive therapy encourages people to discuss their problems and provides them with emotional support. The focus is on sharing information, ideas, and strategies for coping with daily life. Family therapy helps people live together more harmoniously and undo patterns of destructive behavior.

Electroconvulsive therapy

Electroconvulsive therapy, also known as electroshock therapy, shock therapy, or ECT employs a small and carefully controlled current of electricity to induce an artificial epileptic seizure while the patient is under general anesthesia. This therapy may be employed where other means of treatment have failed, or where the use of drugs is unacceptable, such as in pregnancy. In a typical regimen of treatment, a patient receives three treatments per week over three or four weeks. Repeat sessions may be required. Short-term memory loss or headache may result from this treatment.

Transcranial Magnetic Stimulation

Repetitive Transcranial Magnetic Stimulation (rTMS) is currently under study as a possible treatment for depression. Initially designed as a tool for physiological studies of the brain, this technique shows promise as a means of alleviating depression. In this therapy, a powerful magnetic field is used to stimulate the left prefrontal cortex, an area of the brain which typically shows abnormal activity in depressed individuals. Studies currently show an efficacy similar to that of ECT, but with fewer side effects. No sedation is required, and the only reported side effects are a slight headache in some patients, and facial muscle contraction during treatment.

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