Suspected Causes of Depression

Many potential causes of depression have been identified on the basis of research and keen observation. Various of these factors can interact and summate as they determine the course and severity of depressive episodes.

The following is a brief summary of possible causes:

Genetic factors have been implicated by researchers who study the extended families of depressed individuals and find that relatives have a significantly higher incidence of depression than the general population. Closer relatives of depressed persons have higher rates of depression than do distant relatives.

In twin studies identical twins have a much higher chance of both suffering from depression than do fraternal (nonidentical) twins. These kinds of studies could be taken as evidence for the learning of depressed behavior in families as a result of similar experiences, and learning can be an important factor. Adoption studies have also suggest that genetics can play a significant role in the development of depression.

Biochemical factors may also be involved in depression. Neurotransmitters are molecules that move between the neurons (special nervous system cells in the brain) allowing neuro-impulses to travel from one cell to the next. The search is not over, but so far, two specific neurotransmitters have been found to occur at low levels in depressed individuals. It has also possible that these neurotransmitters could be present in sufficient quantity, but may not used effectively by the brain. These neurotransmitters are norepinephrine and serotonin. Anti-depressant medications are known to increase the availability of these brain chemicals and/or to improve the way the brain uses them, thereby relieving depression.

Hormonal factors may also be involved in depression. It has been found that people who are depressed frequently show elevated levels of cortisol. Cortisol is a hormone released by the adrenal glands when individuals are under stress. Stressful events are often found to have preceded episodes of depression. High levels of another hormone named melatonin have also been implicated in depression. It is thought that the lack of sun associated with winter months may cause a build up of melatonin and produce the depression that is called seasonal affective disorder.

Psychological theories have identified many life events that predispose individuals to depression. Psychodynamic theorists have noted that the death or loss of a loved one early in life increases the likelihood of depression for the person experiencing the loss. The separation of children under six from their mothers has been found to lead to a form of child depression (anaclitic depression). These findings also hold for infant monkeys separated from their mothers. It appears that maintaining early emotional attachments with caretakers is very important to mental health of children and the adults that they become.

Behaviorists have observed that depressed individuals have often lost a significant proportion of the rewarding people, places, things, or abilities that they have customarily enjoyed in life. In some individuals a loss of important sources of rewards are thought to precipitate a downward spiral of depression in which these people do fewer things and therefore obtain even fewer rewards in their lives. Also, studies have demonstrated a behavioral contagion effect in which non-depressed people were exposed to other individuals who acted depressed. The findings were that some of those who were simply exposed to a depressed person began to feel depressed themselves.

Cognitive factors refer to a persons beliefs, attitudes and ways of thinking about the world. Cognitive-behavioral research has found that feelings of helplessness accompanying depressed behavior can be produced by repeatedly experiencing painful events over which the individual has no control. More recent changes to this theory note that a perceived lack of control over such painful events is more important than the actual control which is available.

Other psychologists have examined cognitive factors that can lead to depression. For example people can learn to think negatively about their past, present and future. They can also magnify various minor problems and minimize the good things in their lives. Depressed people also frequently have automatic thoughts which they think in a “reflexive”-like and uncritical way. Such thoughts might include things like: "I certainly am damaged goods", “I’ll never amount to anything”, I'm the biggest screw-up on earth", or "I've got so many problems I just can't take it anymore."

It is good that you have taken the time to become familiar with some of the likely factors that may predispose people to periods of depression. Knowing your risk factors could help you to lower some of them. Perhaps you could share this information with your loved ones. Knowing our risk factors can help us all to be more alert for early indications of depression and to seek professional help early.

As always, prevention and early treatment are the best approaches.

Dr. Tom
11/29/09