Major depression is caused by factors relating to chemical substances in the brain, past incidences in family, and psychological disposition. Brain scans showed that there is difference between the brain pictures of normal and depressed people. The specific area that is supposed to be nerve center responsible for cognitive faculties such as mood, thoughts, behavior, rest and dietary habits was observed to be extremely active than normally do. It was also observed that there was imbalance of neurotransmitters in the affected area. These scans, however, do not tell us the cause of depression.

Sometimes depression runs in the generations indicating that there is hereditary factor to depression. But it does not indicate that people who have no hereditary factors do not get depressed. It is understood that hereditary factors act in tandem with other factors in causing depression in people. There are many causes that make onset of depression in people which include stress and anxiety, behavioral problems, trauma, etc. Relapses may occur without any apparent triggers.

Causes of Major Depression

Researchers categorized causes into areas such as organic, psychological and situational. These are the probable causal factors.

Organic Causes: As discussed above, researchers have discovered extreme activity in the functioning of neurotransmitters in people with major depression and also prevalence of hereditary connection to depression. A chemical called cortisol is examined to know its possible effects on people in depression. This chemical is found in blood stream in concentrations whenever a person is confronted with stressful situations like fear, anger or anxiety.

In normal situations, the cortisol level in a person attains peak levels in the early morning periods and gradually decreases and returns to normal during the rest of the day. In depressed people, the cortisol level does not decrease but remains at peak levels throughout the day. But research does not indicate that high level of cortisol is to be blamed for depression nor does it indicate that depression is causing high cortisol levels. But it can be safely said that high cortisol levels are always found in people with depression.

An additional organic factor that was extensively studied in people is the presence of neurotransmitters and the effects of the variations in their concentrations. These neurotransmitters hop across small nerve endings and carry neurological signals. The network of neurotransmitters is controlled by another chemical called serotonin. In depressed people, this serotonin is found to be in low levels than in normal people. That is why a certain branch of medications, called serotonin specific reuptake inhibitors (SSRIs), are prescribed to give relief to depressed people. These medications on depressed people act on receptors in their brain which selectively block reuptake of serotonin which is already in low levels.

Heredity and depression are inter-connected. Generations carry genetic codes connected with depression. Identical twins are a case in example. The causes and triggering factors of depression appear to be at the same level in both the twins. The levels are found to be dissimilar in normal twins.

Psychological Causes: Major depression may grow from our reaction to incidents rather than by the incidents themselves. People may imbibe a negative reaction to an incident or a situation in their mental framework which may later develop into depression. People may become self-critical for the adverse effects. They may attribute any positive happening to their good luck, while they curse themselves for any adverse showing. If this behavior becomes routine, then they start thinking that they are insignificant, incompetent, and mediocre. Sometimes, they may inherit such tendencies from parents.

Vulnerability breeds depression. People who feel vulnerable to events and situations may think that they can not cope with such situations and occurrences. That tendency leads them to depression. A case in point is verbal abuse. Children grow with that in mind and even when they become adults, they display the same tendency of mental resignation.

Situational Causes: People react to the surroundings that they are in. Family happenings such as death of loved ones, parental abuse, marital discord, financial problems, etc., will cause distress and despair which may eventually lead to depression. Occupational happenings such as office tensions, deadlines, targets, loss of job, etc., may create stress and anxiety. Social causes such as social status, sexual discrimination, racial abuse, etc., may add to the tensions.