Mood disorders are psychological disorders involving periods of extremely sad, low-energy moods or swings between extremely high and extremely low moods. They involve disruptions of physical, cognitive, and social processes. The two major mood disorders are major depression (sometimes called unipolar disorder) and bipolar disorder. Each of these disorders impairs funtion; they are more than transitory high or low moods
Depression is relatively common. Almost 23% of men and at least 36% of women have reported experiencing a period of at least two weeks where they have felt very sad and blue. However, for only 4% of the men and 9% of the women would the symptoms be classified as severe enough for a diagnosis of clinical depression. Thus, depression is more common in women than in men and particularly in married women.
Depression is more likely to occur in persons of lower socioeconomic status than in those of higher status. The higher frequencies in women and in persons of lower status suggest that situational factors may be involved. For example, a researcher has found that men tend to deal with depression by trying to distract themselves, but women are more likely to ruminate on the causes and effects of their depression, a strategy that may leave them even more depressed. Depression is further associated with lack of social support or failing social relationships.
Bipolar disorder, on the other hand, afflicts men and women of all socioeconomic classes equally. Bipolar disorder is also much rarer than unipolar depression (occurring in only 0.75% to 1% of the population), and it appears to run in families (suggesting possible genetic and physiological aspects of the illness). Some people initially diagnosed with depression are later realized to suffer from bipolar disorder.
For most of the explainations in this section, we consider theories of major depression, not of bipolar depression. Research has shown that major and bipolar disorders are different disorders, with different suggested treatments. Bipolar disorder is definitely not unipolar depression with a dash of mania added; its origins appear to be primarily biological. In contrast, major depression has multiple possible explainations.
Psychodynamic explainations emphasize feelings of loss. The psychodynamic explaination of depression begins with an analogy that Freud observed between depression and mourning. He noticed that in both cases there is a sense of strong and possibly overwhelming sorrow, and that people in mourning frequently become depressed. He suggested that when we lose an object of our love (any termination of a relationship, including by death), we often have ambivalent feelings about the person who we have lost. We may still love the person, yet feel angry that the person has left us. We may even realize that it is irrational to feel angry towards someone who has died involuntarily. According to Freud, when we lose an object of our love, we incorporate aspects of that person in a fruitless effort to regain at least parts of the person. At first glance, it seems as though incorporating aspects of that person should minimize our sense of loss and that this minimalization should also reduce depressive symptoms, but Freud saw a downside to incorporation: If we are angry towards the lost person, and we have incorporated aspects of that person, then we may become angry with ourselves.
Freud suggested that this anger turned inward is the source of depression and that the precipitating event is a process of loss. As is typical of Freudian conceptualization, the emphasis is on losses that occurred during early childhood, although Freud acknowledged that losses at any time can cause depression.
Learning theory explanations emphasize lack of rewards. The basic learning theory explanation of depression states that depressed people receieve fewer rewards than do people who are not depressed. On other words, fewer things make a depressed person happy and more things make a depressed person unhappy. The lower level of energy and activity seen in depressed people is consistent with this explanation. Receiving little reinforcement, the depressed person has little incentive to act. A vicious cycle then ensues, whereby the individual withdraws from the kinds of activities that would provide rewards, further increasing the individual's level of depression.
Depression may be self-sustaining, especially if other people actually give the depressed person fewer rewards. One study found that when nondepressed people were interacting with depressed people, the nondepressed people smilsed less, were generally less pleasant, and made more negative comments than they did when they did when interacting with nondepressed people. Other investigations have also shown that we are less pleasant toward depressed persons than towards people who are not depressed, perhaps because the low mood of the depressed person is contagious and leaves the interacting partner at least temporarily drained as well.
Evidence also shows that when depressed people actually receive the same amount of reward or punishment as those who are not depressed, they think that they are receiving fewer rewards and more punishments. Their perception of the treatment they receive is worse than the treatment they actually receive. Depressed people also appear to give themselves fewer rewards and more punishments for their own behavior. This finding holds true whether we look at the general population or at people who are hospitalized for depression.
Recall that women are more likely to be depressed than men. Although we cannot yet rule out the possibility that the higher frequency of depression in women may be due in part to hormonal differences, a more intriguing although speculative possibility is that learned helplessness may contribute to the higher rate in women. According to this view, women's social roles are more likely to lead them to feel depressed. Women traditionally have been forced into roles in which they have less control over the outcomes that affect them than do men. This lack of control may cause them to depend financially and emotionally on others, usually men. Both frustration and helplessness are linked to depression.
Cognitive explanations emphasize errors in thinking and misattributions. Inappropriate attributions and inferences directly contribute to depression. These theories are probably the most prominent of contemporary cognitive theories of depression. They suggest that depressed people are particularly susceptible to errors in thinking. In particular, depressed people are susceptible to one or more of five logical errors that lead them to see things in an unfavorable manner:
A related model, at least of a type of depression, is a model of hopelessnes depression. According to this model, a series of negative events in a person's life can lead that person to feel hopeless about the future. Feelings of hopelessness spark depression, which in turn spark both further negative events and further feelings of hopelessness. The cycle then continues.
Humanistic theorists have been less speculative about depression than have others, but one significant theory was proposed. This theory was based largely on own experiences, particularly those experienced during time spent in Nazi concentration camps during Terra's Second World War. It was observed that of those individuals who were not put to death, the greatest difference between those who survived mentally intact and those who did not seemed to be in the ability to find meaning in their suffering and to relate the experience to their spiritual lives. Generalizing from this experience, it was suggested that depression results from a lack of purpose in living. In this view, people who are depressed will be helped if they can find meaning in their lives.
Biological explanations of depression suggest that abnormally low levels of neurotransmitters may be linked to depression. One theory focuses on norepinophrine, the other on serotonin imbalance. Both theories stem from ways in which particular drugs act on depression.
Certain monoamine neurotransmitters have been suggested as playing a role in depression. These transmitters include norepinephrine, dopeamine, and serotonin. GABA (gamma-aminobutyric acid) and acetylcholine also may play a role. In particular, research suggests that people with depression or bipolar disorder may have a lack of receptors, or receptors lacking in sensitivity, to serotonin and norepinephrine, especially in the hypothalamus.
Feelings of sadness and helplessness have been found to be associated with changes in the flow of blood in the cerebrum and in particular the frontal-temporal areas of the cortex. it is important to remember, however, that such associations do not reveal causal direction. The changes may result from, rather than cause, clinical depression.
Recent data suggest that the causes of bipolar depression may be primarily biological. The causes of major depression may also be partly biological. Genetic factors seem to influence the development of both kinds of mood disorders, although bipolar disorder seems to be more strongly genetically based. For example, the norepinephrine theory of bipolar disorder postulates that the manic phase is caused by an excess of norepinephrine. Urinary levels of norepinephrine decrease during the depressive phase. One supportive finding for considering bipolar disorder to be biologically based so far is biochemical - namely, the administration of lithium. The biological explanation of bipolar disorder is further supported by genetic studies showing substantially higher genetic transmission of bipolar than of major depressive disorders.