Phobic Disorders - Biological Explanations of Phobic Disorders

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Genetic Factors Family studies - Research shows that having a family member with a phobia increases the risk that an individual develops a similar disorder. (The family member who already has the disorder is called the proband) Fyer et al (1995) - probands had three times as many relatives who also experienced phobias as the normal controls. Solyom et al (1974) - 45% of phobic patients had at least one relative with the disorder, compared to a rate of 17% of non-phobic controls.	Family and twin studies - There is a considerable variability between disorders. One of the problems with family and twin studies is that they fail to control for shared environmental experiences.
	Behavioural inhibition - Kagan (1994) - identified an infant temperamental type that he described as 'behavioural inhibition' - infants who tend to withdraw from unfamiliar people, objects and situations. He suggested that this behaviour had a genetic basis.
Twin studies - There is a closer concordance between MZ twins than DZ twins, this is because they are genetically identical. This provides support for a genetic basis for phobic disorders. Torgersen (1983) - compared MZ and same-sex DZ twin pairs where one twin had an anxiety disorder with panic attacks. Such disorders were five times more frequent in MZ twin pairs.	Behavioural inhibition - Longitudinal studies have followed children who showed signs of behavioural instability at birth. At primary school age such children were found to have higher ANS activity and also the largest number of specific fears. Similar results were found when looking at children whose parents suffered from panic disorder. Further follow-up studies found that both these groups of children developed significantly more anxiety disorders, supporting the hypothesis that behavioural inhibition to unfamiliar things or situations is genetically based and a risk factor for anxiety disorders.
	The diathesis-stress model - Even at the highest rates it is clear that phobic disorders are not solely genetic and have other factors. This combination can be explained by the diathesis-stress model. This proposes that genetic factors predispose an individual to develop phobias but life experiences play an important role in triggering such responses.
An Evolutionary Approach Ancient fears - Some stimuli are more likely to be feared than others, these could be referred to as ancient fears, in that these stimuli reflected very real fears to our ancestors. Many other stimuli were also part of our ancestral environment, but because they posed no significant danger, are rarely feared. For the same reason, things that are dangers today rarely develop into phobias because they have not been around enough to have influenced our adaptive selection.	Clinical phobias - A lot of the research into prepotency and preparedness that we have looked at is concerned with avoidance responses rather than clinical disorders. Studies of patients suffering from disabling disorders do not support the preparedness explanation. In addition, research has found that clinical phobias do not display the suddenness of onset and resistance to treatment predicted by preparedness.
	Cultural differences - There are significant differences in the kind of phobias reported by different cultural groups. Brown et al (1990) - found that phobic disorders were more common among African American than white American participants even when socioeconomic factors were controlled. This shows that environmental/social factors are important in determining aspects of phobias.
Prepotency - Animals have evolved to respond to potential threats. Those ancestors who were able to respond appropriately to ancient threats were more likely to survive and pass on their genes to subsequent generations. Preparedness - Seligman (1970) - argued that animals, including humans, are biologically prepared to rapidly learn an association between particular (potentially life-threatening) stimuli and fear. Once learned, this fear is difficult to get rid of.	Prepotency - Öhman and Soares (1994) - provided supporting evidence for prepotency effects. 'Masked' pictures were constructed of feared objects in such a way that the animals in the pictures were not immediately recognisable. Participants who were fearful of snakes or spiders showed greater GSR which indicates arousal of the ANS, when briefly shown 'masked' pictures compared to viewing neutral pictures or compared to normal participants. This shows that important components of phobic responses are set in motion before the phobic stimulus is presented in awareness, and these could be prepotent signs.
	Preparedness - The two important predictions arising from the concept of preparedness are: That we learn certain fears more readily Such fears are harder to unlearn McNally (1987) - concluded that although there was firm evidence for enhanced resistance to extinction of fear responses conditioned by 'prepared' stimuli, evidence for rapid acquisition of 'modern' phobias.