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Mental disorders
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Help The Neurobiology of Depression Quelles sont les causes de la dépression? The Anatomy of Stress" Part 1 of 3
Current theories on the causes of depression Dr. Ivan's DEPRESSION CENTRAL Les troubles de l’humeur Psychomedia
Depression: Beyond Serotonin
Greg Siegle, Ph.D.

In some cases of depression, it is hard to discern any particular triggering event. Such depressions are described as endogenous (or, to use an older term, melancholic). Individuals with endogenous depression see themselves as the only possible source of their suffering and think that everything is their own fault. Their emotional pain is absolutely unaffected by the attitudes of the people around them. For such patients, treatment with antidepressants is often spectacularly successful.

In contrast, cases of reactive depression are associated with recent events or conflictual psychological situations. Individuals with reactive depression feel isolated and abandoned. Very often, they see what is happening to them as someone else's fault. They therefore tend to see themselves much more as victims than as guilty parties (the opposite of how people with endogenous depression see themselves). People with reactive depression often develop somatic symptoms and make suicide attempts, but these often represent a cry for help, a way of mobilizing support from the people around them.

The kinds of events that are often the cause of reactive depression include a death in the family, a relationship breakdown, or a business failure. But sometimes even problems that might seem trivial to an outside observer undermine an individual's self-esteem so seriously that they can lead to reactive depression. In such cases, the slightest experience that bolsters self-esteem can lead to dramatic improvements.



Debbie Aldridge/Illustration Services photo


Psychiatrists generally consider an individual to be suffering from depression when he or she presents a set of symptoms that include a morbid state of mind, a generalized sadness that pervades all areas of life, a loss of interest and pleasure in most activities, and a slowing of mental and motor activity, and when these symptoms persist every day for at least two weeks.

Most likely, the symptoms of depression actually reflect several distinct psychological mechanisms. These differences might explain why certain treatments with antidepressants have a beneficial effect on some patients but none at all on others.

Though we do not know the exact causes of depression, we do know that a number of factors contribute to its development. These factors interact, so that depression, rather than having a single cause, usually occurs when a number of unfavourable circumstances coincide in a person's life. These contributing factors can be classified into the following three categories.

Environmental factors

Environmental factors are events external to the individual that can contribute to the development of depression. Examples include the death of a loved one, divorce, job loss, financial problems, and a disabling illness or injury.

It is estimated that nearly half of all cases of depression are related to stressful situations. Also, several studies have shown that stress at an early age can predispose an individual to develop depression in adult life. In light of the harmful effects that chronic activation of the stress axis is known to have on neurogenesis, it is not surprising that inhibition of action can seriously predispose someone to depression.

Psychological factors

A person's history—whether they had a hard childhood or, on the contrary, were given lots of encouragement and opportunities to grow and flourish—shapes their personality and makes them more or less susceptible to depression.

People who are constantly having problems in their relationships, or trouble in communicating, or feelings of loneliness are at a greater risk of experiencing depressive episodes. The lack of a close, trusting relationship, whether with a friend or with a lover, can also increase the risk of depression. The quality of the support that we receive from our interpersonal relationships thus helps to reduce our physical and emotional reactions to stress and thereby protect us from depression.

  Genetic (hereditary) factors

We now know that some genetic factors that affect the functioning of the brain may make people more vulnerable to depression.

For example, people with close relatives who have suffered from depression have a 15% risk of developing it themselves, while people with no such relatives have only a 2 to 3% chance. Interestingly, children who are born to parents with histories of depression but adopted by parents with no such histories still have a 15% risk of developing this condition. In identical twins (who have exactly the same genes), the probability that one twin will experience depression if the other has done so jumps to 70%.

Even though certain genes are implicated in depression, they do not seem to trigger this illness inevitably. Instead, they simply transmit a susceptibility to falling into depressive states more readily—a greater likelihood that given the individual's particular personality traits, or a particular external event, he or she might develop clinical depression.

It is also important to realize that regardless of whether the factor or factors that trigger a depressive episode are environmental, psychological, or genetic, they will inevitably affect the activity of certain areas and certain neurotransmitters in the brain. In the final analysis, it is these physiological disturbances that are the proximal cause of the symptoms of depression. In contrast, the environmental, psychological, and genetic factors may be regarded as distal or ultimate causes. That is why it can be so important to try to trace these symptoms back to their ultimate causes through psychotherapy. For psychotherapy to succeed, however, the patient may sometimes have to be treated with medication first.


Depression can be regarded as an emotional disorder in which certain emotions are experienced very intensely. It is thus distinguished from psychotic disorders, which are related more to disordered thoughts. Sometimes, however, a depression can be so emotionally intense that it results in cognitive problems as well.


Causes of Depression Bipolar Disorders Link: Bipolar Disorder LA MANIACO-DEPRESSION
Link: Guide to Bipolar Disorder

Bipolar disorder involves mood disturbances that are manifested in phases of depression followed by phases of excitation (mania), which is why this disorder was long known as manic depression. These phases can vary in intensity and are sometimes interspersed with normal periods where the individual functions relatively well.

In the manic phase, the individual is in a state of extreme excitation. He or she may try to do several things at once and display mood swings from euphoria to aggressiveness.This manic phase is followed by a depressive phase, which comes on over the course of a few days or weeks. The individual then feels tired and irritable and no longer shows any interest in his or her surroundings or usual activities.

Manic depression affects both men and women and usually appears between ages 25 and 30. Though major depressive episodes can occur in childhood, outright manic episodes do not appear until after puberty. Left untreated, bipolar disorder generally grows worse over the years, so it is essential to treat it as soon as possible.

Though the exact causes of manic depression have not been determined, it is now agreed that several factors lie at its origin. The genetic factors are especially significant, because among adults age 18 and over, the risk of developing this disease ranges from 0.3 to 1.6% in the general population, but is far higher—15 to 25%—for people with collateral or first-degree relatives who had the disease.

Genetic factors thus go part of the way toward explaining manic depression, but not all of the way, because studies show that it occurs only 50 to 65% of the time in both members of a pair of identical twins. As with major depression, environmental and psychological factors also appear to be involved.

Accumulated stress due to problems of everyday life can trigger both depressive and manic episodes. The seasons also apparently can influence mood disorders: mania is more frequent in summer and fall, and depression is more common in winter.

A number of different genes are involved in manic depression, some of them on different chromosomes—18, 21, and X in particular. The role of the X chromosome would explain why genetic susceptibility to this disease is transmitted more readily through the mother than through the father.

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