Analyze etiologies (in terms of biological, cognitive and/or sociocultural factors) of one disorder from two of
the following groups: anxiety disorders, affective disorders, eating disorders.
Etiology means the scientific study of causes or origins of diseases or abnormal behavior. The reason psychiatrists are interested in etiology is the assumption that treatment should be related to the cause of the disorder, e.g. if the disorder is biological in origin, the treatment should also be biological (the biomedical model). This unit will analyze etiologies of one affective disorder (major depression) and one eating disorder (bulimia nervosa).
Affective disorder: major depression
Neurotransmitters: The serotonin hypothesis
Henninger et al. (1996) performed experiments where they reduced serotonin levels in healthy individuals to see if they would develop depressive symptoms. The results did not support that levels of serotonin could influence depression and they argued that it is necessary to revise the serotonin hypothesis.
Kirsch et al. (2002) found that there was publication bias in research on effectiveness of SSRI in depression. In fact, if the results of all studies (including the ones that had not been published) were pooled it would seem that the placebo effect accounted for 80% of the anti-depressant response. Of the studies funded by pharmaceutical companies, 57% failed to show a statistically significant difference between anti- depressant and a neutral placebo. This and similar studies cast doubt on the serotonin hypothesis.
Evaluation of the serotonin hypothesis of depression: There is some evidence that serotonin may be involved in depression and that this may be linked to stress and stress
hormones such as cortisol.
Scientific research has failed to show a clear link between serotonin levels and depression. The fact that anti-depressant drugs like the SSRIs can regulate serotonin levels and produce an effect does not mean that low serotonin levels cause depression.
Genetic predisposition .
This theory of genetic predisposition is based on the assumption that disorders have a genetic origin. In order to study this, researchers study twins and families. In the twin method both monozygotic twins (MZ) and dizygotic twins (DZ) are compared. MZ twins share 100% of their genes but DZ twins share only around 50%. The assumption is that if a predisposition for a psychiatric disorder is inherited, then concordance rates should be higher in MZ twins than in DZ twins. If one twin is diagnosed with a disorder and the other twin is also diagnosed with the same disorder, the twins are said to be concordant.
Nurnberger and Gershon (1982) reviewed seven twin studies on major depression. The results indicated that genes could be a factor in depression. The concordance rates for major depression were consistently higher for MZ twins (65% on average across the studies) than for DZ twins (14%). This supports the theory that genetic factors could predispose people to depression. Since the concordance rate is far below 100% nothing definite can be said about genetic inheritance except that environmental and individual psychological factors could also play an important role in etiology. There is also the problem with co-morbidity: people suffering from depression often suffer from other psychological disorders as well (e.g. anxiety, and eating disorders).
This approach to etiology deals with the role of “thinking” and “negative cognitive schemas” called “depressogenic schemas”.
Beck (1976) Cognitive theory of depression (negative cognitive triad)
· according to this theory depression is caused by inaccurate cognitive responses to events in the form of negative thinking about oneself and the world. People’s conscious thoughts are influenced by negative cognitive schemas about the self and the world (depressogenic schemas). This results in negative automatic thoughts and dysfunctional beliefs. This explanation is contrary to traditional theories about depression where negative thinking is seen as a symptom of depression and not the cause.
· Beck’s theory can be seen within the diathesis-stress model of depression. Depressive thinking and beliefs (depressogenic schemas) are assumed to develop during childhood and adolescence as a function of negative experiences with parents or other important people. The depressogenic schemas constitute a vulnerability (diathesis) that influences an individual’s reaction when faced with stressors (e.g. negative life events or rejection). Such events tend to produce negative automatic thoughts (cognitive biases) based on three themes: negative thoughts about the self, the world, and the future (negative cognitive triad).
Evaluation of Beck's cognitive theory of depression
· The theory is effective in describing many characteristics of
depression. For example, depressed individuals are considerably more negative in their thinking than non-depressed individuals. People who suffer from depression generally think more negatively about themselves and the world, even when they are not depressed.
· The limitation of Beck’s theory is perhaps that it is difficult
to confirm that it is the negative thinking patterns that
cause depression but there has been some empirical
support of the causal aspects of the theory.
Social factors such as poverty or living in a violent relationship have been linked to depression. Women are more likely to be diagnosed with depression than men and one reason could be linked to the stress of being responsible for many young children and lack of social support.
Brown and Harris (1978) Social factors in depression
To investigate how depression could be linked to social factors and stressful life events in a sample of women from London (vulnerability-stress model of depression).
In London, 458 women were surveyed on their life and depressive episodes. The researchers used interviews where they addressed particular life events and how the women had coped.
In the previous year, 37 women (8% of all the women) had been depressed. Of these, 33 (90%) had experienced an adverse life event or a serious difficulty. Working-class women with children were four times more likely to develop depression than middle-class women with children. The researchers found that vulnerability factors such as lack of social support, more than three children under 14 years at home, unemployment and early maternal loss, in combination with acute or ongoing serious social stressors, were likely to provoke depressive episodes.
The study was exceptional in that it showed that social factors (and not only personality factors) were involved in development of depression. The results were extremely important at establishing a new approach in understanding depression. Etiology of depression now often includes consideration of social factors. The sample in the study was gender biased (only female respondents) so it is not possible to generalize the findings to men. The semi-structured interview was useful to gather in-depth information of how the women perceived their own situation.
Eating disorder: Bulimia nervosa
Bulimia nervosa is a serious psychological disorder characterized by binge eating episodes followed by compensatory behaviors such as dieting, vomiting, excessive exercise and misuse of laxatives.
Kendler et al. (1991) Twin research to study genetic vulnerability in bulimia nervosa
To investigate risk factors and genetic inheritance in bulimia nervosa
A sample of 2,163 female twins participated in the study. One of the twins in each pair had developed bulimia. The study was longitudinal and the researchers conducted interviews with the twins to see if the other twin would develop bulimia and if concordance rates were higher in monozygotic twins (MZ) than in dizygotic twins (DZ).
Overall the concordance rate for bulimia was 23 % in MZ twins compared to 9% in DZ twins.
Body-image distortion hypothesis
Weight-related schemata model
Fairburn (1997) suggested that people with eating disorders had distorted weight-related schema and low self-esteem. The distorted beliefs and attitudes towards body shape and weight develop partly because of the high status given to looking thin and attractive. Individuals strive to control body weight to stay thin and they base their self-worth on being thin, i.e. they have a weight-related self-schema that distorts the way they perceive and interpret their experiences. For some people, their concerns and prioritization of weight control may reflect a wider lack of self-esteem and a vulnerability to cultural messages about body weight. They think they will feel better if they lose weight but this obsession with weight control may lead to depression and intensified feelings of low self-esteem because weight control is the major way of maintaining self-worth.
Perceptions of the perfect body are influenced by cultural ideals. In the West, images of the ideal body shape for women have changed over the years from an hourglass shape to a slimmer shape.
Levine et al. (1994) investigated the relationship between sociocultural factors and eating attitudes and behaviors.