Causal Factors of Mood Disorders

Mood disorders, much like anxiety disorders, are a product of interacting biological, psychological, and environmental factors.

Biological factors

Both neurological and genetic factors have been linked to depression; genetic factors surface in both twin and adoption studies. In identical twins, there is a higher concordance rate of experiencing clinical depression compared to fraternal twins. Among adopted people who develop depression, biological relatives have a higher chance of suffering from depression than adoptive relatives and a predisposition to depressive disorders is more likely to be inherited given certain kinds of environmental factors such as a significant loss, or low social support.

Influential Theory

Considering biological research, the focus has increased on the role of brain chemistry in depression. According to Influential Theory, depression is a disorder of motivational underactivity of a family of neurotransmitters, including dopamine, serotonin, and norepinephrine. These transmitters play important roles in several regions of the brain involved in reward and pleasure.

When neural transmissions in these brain regions decrease, it results in lack of pleasure, and motivational loss, which are characteristics of depression. In support of this theory, several effective antidepressants operate by increasing the activity of these neurotransmitters, further stimulating the neural system which underlies positive mood and goal-directed behaviour.

A study headed by Lescia Tremblay tested the amount of reward experienced by depressed patients when a stimulant drug was used to activate these centres, and individuals who were in severe depression showed a much stronger level of pleasure response to the drug, supporting the hypothesis of a deficit of pleasure in the brain.

Genetic Basis

Later research by Ian Gotlib with the use of fMRI (functional Magnetic Resonance Imaging) readings of emotion areas of the brain showed low neuron responsiveness to happy and sad scenes alike, as if the emotional response system had shut down. This may account for lack of positive emotionality and the empty feelings of depressive emotional experience.

Bipolar Disorder, in which depression alternates with less frequent manic periods, has been studied primarily at a biological level because it tends to have a stronger genetic basis than unipolar depression. Around 50% of patients with the disorder have parents, grandparents, or a child with bipolar disorder as well. Identical twins have a higher chance of developing bipolar disorder than fraternal twins, which suggests a genetic cause.

Manic disorders may stem from an overproduction of the same transmissions which are underactive in depression. Lithium chloride, which is most frequently used to calm manic disorders, is used to decrease the activity of these transmitters in the brain's motivational and pleasure activation system.

Psychological factors

Biological factors can cause a person to be more vulnerable to certain types of psychological and environmental events that can trigger such disorders.

Personality-based Vulnerability

According to the beliefs of psychoanalysts Sigmund Freud and Karl Abraham, early traumatic losses or rejection create vulnerability for later depression by creating a grieving and rage process which becomes part of the individual's personality. Subsequent losses and rejections cause the reactivation of the original loss, causing a reaction not just about the current event, but unresolved losses from the past, too.

British sociologists George Brown and Terrill Harris support Freud's theory of early loss. According to Brown and Harris, out of the women they interviewed in London, the rate of depression was three times higher among those who lost their mothers under the age of 11 and experienced severe recent losses than the women who had similar recent losses but no such previous loss. Experiencing the death of a parent in early childhood can cause an increased risk of depression later in life.

Cognitive process

According to Aron Beck, depressed individuals tend to victimize themselves with the beliefs that they are defective, inadequate and worthless. They feel that everything that happens to them is bad and that bad things will continually happen to them because of their personal defectiveness.

This depressive cognitive triad of negative thoughts concerning the world, oneself, and the future tends to pop up into the conscience automatically. Many depressed people are unable to control or suppress negative thoughts. Depressed individuals recall their failures more often than their successes and tend to focus more on their perceived inadequacies. They detect pictures of sad faces at times of lower exposure times and remember them better than individuals with no depressive disorders, which indicates a perpetual and memory sensitivity to the negative.

Most people take personal credit for the good outcomes in their lives, blaming their misfortunes on outside factors; thereby maintaining and enhancing their self-esteem. This is the opposite of what depressed people do, according to Beck. These individuals exhibit a depressive attributional pattern, which is attributing success or other positive events to factors outside oneself, while attributing negative outcomes to personal factors. According to Beck, not taking credit for success but in addition, blaming themselves for failures helps depressed individuals maintain low self-esteem and beliefs that they are failures.

Learned Helplessness

Another prominent cognitive account of depression referred to as Learned Helplessness Theory holds that depression occurs when people expect the occurrence of bad events and feeling unable to do anything to prevent or cope with them. Even though the depressive attributional pattern plays a central role in the learned helplessness, model learned helplessness theorists have taken it a step further by specifying what the negative attributions for failures are like.

According to them, chronic and intense depression is a result of negative attributions for personal failures. These people, who attribute negative events in their lives to factors such as low levels of intelligence, physical repulsiveness, or an unlovable personality tend to believe that their personal defects will render them helpless, making them unable to avoid negative future events This sense of hopelessness places them at a significantly higher risk of depression.

Behavioural Perspective

The behavioural perspective also has important things to say about depression. According to Peter Livingston, depression is usually triggered by a loss, punishing event, or by a drastic decrease in the amount of positive reinforcement received by an individual's environment. When depression takes hold, people stop performing behaviours that provided them with reinforcement, such as hobbies and socialising.

Depressed individuals, at times, tend to make others anxious. Those persons may lose patience due to their failure to understand why this individual doesn't break the cycle. This can further diminish social support and may cause depressed individuals to be abandoned by those most important to them. According to longitudinal studies, reduction in social support is a good predictor for subsequent depression.

Positive Reinforcement

According to behavioural theorists, for depressed individuals to feel better, they need to break this vicious cycle by forcing themselves to engage in behaviours that would provide them with some degree of pleasure. Eventually, positive reinforcement produced by the process of behavioural activation will begin counteracting the depressive affects undermining the feelings if hopelessness that characterise depression and thereby increasing feelings of personal control over the environment.

Environmental factors may help explain the reason depression tends to run in families. Constance Hammen studied family histories of depressed individuals; his conclusion was that children of depressed parents often experience poor parenting and many stressful experiences growing up. This may result in poor coping skills and a negative self-concept, making them more vulnerable later in life to stressful events, which may trigger depressive reactions. This conclusion is supported by findings that children of depressed parents exhibit a significantly higher incidence of depression and other disorders as adolescents and young adults.

Sociocultural factors

Depression exists virtually in all cultures; but its prevalence, symptom patterns, and causes reflect cultural variations. For example, Hong Kong and Taiwan have a far lesser prevalence rate of depressive disorders compared to Western countries. Individuals in these societies tend to have strong social support from family and other groups, and this helps them through the occurrence of negative impacts of loss and disappointment.

Cultural factors, too, can affect the way depression manifests. For example, in Western European countries and North America, there is a predisposition to feelings of guilt and personal inadequacy. On the other hand, people of Latin, Chinese, and African cultures more often tend to suffer from somatic symptoms of fatigue, loss of appetite, and sleep difficulties.

Finally, according to cultural factors in technologically-advanced countries such as Canada and the United States, women have been reported to be twice as depressed than men. Yet, this sex difference is not evident in developing countries.