Analyze etiologies

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

Biological factors

Neurotransmitters: The serotonin hypothesis

  • The serotonin hypothesis suggests that depression is caused by low levels of serotonin (Coppen, 1967). Serotonin is a neurotransmitter produced in specific neurons in the brain and they are called “serotonergic neurons” because they produce serotonin.
  • Anti-depressants in the form of selective serotonin reuptake inhibitor (SSRI) block the reuptake process for serotonin. This results in an increased amount of the serotonin in the synaptic gap. The theory is that this increases serotonergic nerve activity leading to improvement in mood.
  • SSRI drugs such as Prozac, Zoloft, and Paxil are now among the most commonly sold anti-depressants and this has been taken as indirect support of the serotonin hypothesis. According to Lacasse and Leo (2005) this is an example of backward reasoning. Assumptions about the causes of depression are based on how people respond to a treatment and this is logically problematic.


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).

Cognitive factors


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.

Sociocultural factors


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.

Biological factors

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.


  • The results indicate a heritability of 55%, but this leaves 45% for other factors. Genetic vulnerability may predispose an individual but other factors trigger the disorder and it is important to investigate environmental factors that might interact with the genetic predisposition. The study was a “natural experiment” so the researchers did not manipulate variables and there was no control, so it is not possible to establish a cause-effect relationship.
  • The participants were all women so the findings cannot be generalized to men. It is also questionable whether twins are representative of the population.
  • The study does not take environmental factors into account. It could be that twins grow up in the same dysfunctional environment. It is very difficult to find out the relative importance of genetic inheritance and environmental factors.

Cognitive factors

Body-image distortion hypothesis

  • Bruch (1962) claimed that many patients with eating disorders suffer from the cognitive delusion that they are fat. It may be that when patients evaluate their own body size, they are influenced by emotional appraisal rather than their perceptual experience.
  • Fallon and Rozin (1985) showed nine pictures of different body shapes, from very thin to very heavy, to 475 US undergraduates of both sexes and asked them to indicate the body shape (1) most similar to their own shape, (2) most like their ideal body shape, and (3) the body shape of the opposite sex to which they would be most attracted. Women consistently indicated that their current body shape was heavier than the most attractive body shape. Their ideal body shape was also much thinner than the one they had chosen as similar to their own body shape. Men chose very similar figures for all three body shapes. The researchers concluded that men’s perceptions helped them stay satisfied with their body shape whereas women’s perceptions put pressure on them to lose weight. These sex differences could probably be linked to a higher prevalence of dieting, anorexia, and bulimia among American women than among American men.

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.

Sociocultural factors

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.

  • In the USA, 385 middle school girls (aged 10–14 years) answered questions about eating behavior, body satisfaction, concern with being slender, parents’ and peers’ attitudes, and magazines with regard to weight management techniques and the importance of being thin.
  • The majority of the respondents said they received clear messages from fashion magazines, peers and family members that it is important to be slim. They also said that  the same sources encouraged dieting or other methods to keep a slender figure.
  • The study found two important factors in the drive for thinness and disturbed patterns of eating: (1) reading magazines containing information about ideal body shapes and weight management and (2) weight-related or shape-related teasing or criticism by family.
  • The results indicate that body dissatisfaction and weight concerns reflect sociocultural ideals of a female role and raises the possibility that some adolescent girls live in a subculture of intense weight and body-image concern that places them at risk for disordered eating behavior such as bulimia nervosa.