What is Depressive Disorder and How Does it Affect the Quality of Life?

Some types of depression run in families, indicating that a biological vulnerability to depression can be inherited. .This seems to be the case especially with bipolar disorder. Studies have been done of families in which members of each generation develop bipolar disorder. The investigators found that those with the illness have a somewhat different genetic makeup than those who do not become ill. However, the reverse is not true. That is, not everybody with the genetic makeup that causes vulnerability to bipolar disorder has the illness. Apparently, additional factors, possibly a stressful environment, are involved in its onset.

Major depression also seems to occur in generation after generation in some families, although not as strongly as in Bipolar I or II. Indeed, major depression can also occur in people who have no family history of depression.

An external event often seems to initiate an episode of depression. Thus, a serious loss, chronic illness, difficult relationship, financial problem, or any unwelcome change in life patterns can trigger a depressive episode. Very often, a combination of genetic, psychological, and environmental factors is involved in the onset of a depressive disorder.

Nothing in the universe is as complex and fascinating as the human brain. The over 100 chemicals that circulate in the brain are known as neurochemicals or neurotransmitters. Much of our research and knowledge, however, has focused on four of these neurochemical systems: norepinephrine, serotonin, dopamine, and acetycholine. In the new millennium, after new discoveries are made, it is possible that these four neurochemicals will be viewed as the "black bile, yellow bile, phlegm, and blood" of the twentieth century.

Different neuropsychiatric illnesses seem to be associated with an over-abundance or a lack of some of these neurochemicals in certain parts of the brain. For example, a lack of dopamine at the base of the brain causes Parkinson disease. Alzheimer dementia seems to be related to lower acetylcholine levels in the brain. The addictive disorders are under the influence of the neurochemical dopamine. That is to say, drugs and alcohol work by releasing dopamine in the brain. The dopamine causes euphoria, which is a pleasant sensation. Repeated use of drugs or alcohol, however, desensitizes the dopamine system, which means that the system gets used to the drugs and alcohol. Therefore, a person needs more drugs or alcohol to achieve the same high feeling. Thus, the addicted person takes more and more to feel less and less high.

The different types of schizophrenia are associated with an imbalance of dopamine (too much) and serotonin (poorly regulated) in certain areas of the brain. Finally, the depressive disorders appear to be associated with altered brain serotonin and norepinephrine systems. Both of these neurochemicals are lower in depressed people. Please note that I specified, "associated with" instead of, "caused by." I made this distinction because we really don't know whether low levels of neurochemicals in the brain cause depression or whether depression causes low levels of neurochemicals in the brain.

What we do know is certain medications that alter the levels of norepinephrine or serotonin can alleviate the symptoms of depression. Some medicines that affect both of these neurochemical systems appear to perform even better or faster. Other medications that treat depression primarily affect the other neurochemical systems. The most powerful treatment for depression, electroconvulsive therapy (ECT), is certainly not specific to any particular neurotransmitter system. Rather, ECT, by causing a seizure, produces a generalized brain activity that probably releases massive amounts of all of the neurochemicals.

Women are twice as likely to become depressed as men. However, scientists do not know the reason for this difference. Psychological factors also contribute to a person's vulnerability to depression. Thus, persistent deprivation in infancy, physical or sexual abuse, clusters of certain personality traits, and inadequate ways of coping (maladaptive coping mechanisms) all can increase the frequency and severity of depressive disorders, with or without inherited vulnerability.