Some theories of abnormal affect take a nature perspective whereas others take a nurture perspective. Use evidence to justify why either nature/nurture is more important in explaining abnormal affect. 
The nature/nurture debate is concerned with the extent to which particular aspects of behavior are a product of either inherited (i.e. genetic) or acquired (i.e. learned) characteristics. Nature is that which is inherited / genetic. Nurture which refers to all environmental influences after conception, i.e. experience. The nurture perspective suggests that learned helplessness plays a role in explaining depression. Seligman and Maier (1967) found that the effects of learned helplessness in animals were similar to the symptoms of depression in human. For example, animals that had been trained to be helpless passively accepted their situation and showed other symptoms of depression.
Seligman’s study has led to many lab experiments with humans in an attempt to discover whether people that were trained to be helpless would act accordingly and display symptoms of depression. The theory of learned helplessness has produced a plausible explanation of the relationship between helplessness, attributional style and depression. A lot of research supports this theory. However, there has been some concern about Seligman’s application of research from non-human animals to humans. Evidence from animal studies cannot be generalized to humans, though it can provide important leads. Additionally, much of the evidence for humans comes from laboratory experiments in which the participants are college students and are therefore unrepresentative.
Furthermore, Abramson et al. (1978) updated Seligman’s learned helplessness theory to include the attributions that people make of their own behavior. An attribution is an explanation of why something happens. People suffering from depression tend to make internal, global and stable attributions and blames themselves for their failures. Cognitive behavioral researchers argue that attributional styles derive from a person’s learning history, especially in the family and school. Some researchers argue that a depressive attributional style comes from childhood experiences that predispose certain people to depression.
However, the problem is whether this type of thinking is the cause of depression, or whether it is the effect, of being depressed (but this has not been proven). The nature perspective, on the other hand, suggests that people inherit a biological predisposition to develop an abnormal affect. For example, twin studies suggest that if one MZ twin has bipolar disorder then the odds are about 79% that the other MZ twin also has bipolar disorder. This contrasts with the findings that the odds for DZ twins are about 25 %. In all, about 80-90% of people diagnosed with bipolar disorder have a family history of either bipolar or major depression.
Furthermore, over activity of norepinephrine is implicated in bipolar disorder. Post et al. (1980) has found that norepinephrine activity of a person with mania is higher that that of depressed or control subjects. Telner et al. (1986), however, suggests that patients with bipolar disorder were given reserpine, the blood pressure drug known to reduce norepinephrine activity in the brain, and the manic symptoms of some subsided. However, genetic models are not able to explain the timing and severity of the symptoms present.
Because mood disorders are characterized by so many different symptoms, most researchers think that these disorders will eventually be related to a set of genes, rather than a single gene. Lastly, even if we can identify the genes involved in mood disorders, many questions still remain about how they will work. It is unlikely that genes will simply control whether or not a person develops depression, rather genes may guide the way people regulate emotions or respond to life stressors. They may as well have set the stage for mood disorders to occur when other conditions are present.