Specific Phobias
Symptomatology for Specific Phobia and Terms
The Diagnostic and Statistical Manual of Mental Disorders, fourth edition lists a number of criteria for the diagnostic category of specific phobia. Briefly, DSM-IV emphasises that specific phobias are directed at a limited set of stimuli (e.g., spiders) and that confrontation with these stimuli elicits intense fear and avoidance behaviour. Furthermore, DSM-IV stresses that the fear is excessive and unreasonable to such a degree that it interferes with daily life. These characteristics deserve some comment.
To begin with, it is important to recognise that specific fears are non-randomly distributed. A number of fear survey studies have shown that in the general population, some fears (e.g., fear of spiders or snakes) are far more prevalent than others (e.g., fear of electricity). In other words, most specific fears and phobias pertain to a relatively narrow class of stimuli. Seligman,O ¨ hman, Marks and Nesse have interpreted this phenomenon in terms of evolutionary processes . According to these authors, inspection of this narrow class of stimuli reveals that it consists of objects and events that were probably threatening to prehistoric man.
They assume that fear of animals such as spiders and snakes promoted the survival chances of our prehistoric ancestors. As a result of natural selection, fear of these evolutionary dangers became genetically coded in the form of a primitive learning mechanism. Consequently, modern man would still possess a biological readiness or preparedness to develop specific fears of spiders, snakes and so forth. While this ‘‘evolutionary preparedness’’ hypothesis has attracted considerable attention, other plausible interpretations of the selectivity of fears do exist.
For example, it might well be the case that the selectivity of specific fears is a consequence of the negative connotations that certain stimuli have in our culture. Whatever its origins, the non-random distribution of specific fears is a wellestablished phenomenon. In fact, the DSM-IV differentiates between four highly prevalent categories of specific phobia: animal type (e.g., spider phobia), natural environment type (e.g., phobia of heights), blood-injection-injury type (e.g., dental phobia), and situational type (e.g., claustrophobia). In addition, the DSM-IV introduces a miscellaneous category (‘‘other type’’) which encompasses, for example, choking phobia. Largely, this taxonomy of specific phobias nicely fits with data that come from factor analytic studies. A second point that must be considered is the nature of intense fear emotions.
A good framework for discussing this point is the ‘‘three-systems model’’ proposed by Lang (Lang, see also Hugdahl, . According to this model, emotions such as fear consist of three relatively independent components: a physiological component, a subjective component, and a behavioural component. Thus, fear is reflected in autonomic symptoms (e.g., tachycardia, increased respiration, etc.), subjective feelings of apprehension, and avoidance or escape behaviour. However, the extent to which these components co-occur varies. Thus, it is conceivable that a mild fear of, say, spiders is accompanied by behavioural avoidance of spiders, but relatively little autonomic reactions when confronted with spiders. Although such discordance between components is not uncommon, there are reasons to believe that discordance will be less evident when fear is intense. Nevertheless, the three-systems model has important implications for the study of specific phobias.
To begin with, the model suggests that in diagnosis or therapy outcome evaluation, it is important to measure each component. It should be noted that good measurement instruments are available for each component. More specifically, the physiological component can be monitored using psychophysiological techniques, the subjective component can be quantified with specially constructed and validated self-report instruments, while the behavioural component can be measured by standardised approach tasks . The idea that one should assess all three components when studying phobic fear seems self-evident, but, as a matter of fact, studies in this area often either rely on one or two measures or make use of vague and imprecise instruments to tap the three components. It is worthy of note that not all types of specific phobias display a comparable profile concerning the three components.
For instance, both animal phobia and blood-injection-injury phobia are accompanied by subjective reports of distress. However, whereas in animal phobia distress usually takes the form of fear , blood-injection-injury phobia is associated with strong subjective feelings of disgust and repulsion. Also, confrontation with the phobic stimulus elicits sympathetic activation (e.g., tachycardia) in animal phobia, but parasympathetic activation (e.g., bradycardia) in blood-injection-injury phobia. Thus, the heightened arousal that occurs in animal phobics who are exposed to their feared stimulus stands in sharp contrast to the lowered arousal seen in bloodinjection- injury phobia. Referring to the peculiar characteristics of blood-injection-injury phobia (i.e., subjective feelings of disgust, bradycardia, and fainting), some authors have argued that the term bloodinjection- injury phobia is a misnomer. According to these authors, blood phobics do not fear blood, but the consequences of confrontation with blood (e.g., fainting).
This would imply that there is an interesting connection between blood-injection-injury phobia and panic disorder inasmuch as both conditions are characterised by fear of bodily sensations. As far as the content of subjective fear is concerned, there are also major differences between situational phobia, in particular claustrophobia, on the one hand, and animal phobia, on the other hand. Subjective fear in claustrophobia is not only focused on danger expectations (e.g., fear of suffocation), but also on anxiety
expectancies (e.g., fear of going crazy) and bodily sensations. The latter components are less prominent in animal phobias . Thus, from a cognitive point of view, claustrophobia seems to represent a more complex fear than animal phobia. Indeed, a close look at the subjective cognitions that are involved in specific phobias makes clear that these phobias do not constitute a homogeneous class.
Another characteristic of specific phobias that requires some elaboration is their irrational nature. The patient suffering from, say, an intense spider phobia readily admits that her or his fear is excessive. Nevertheless, she or he is unable to inhibit fear responses when exposed to spiders.
How can one account for this failure to control fear responses?
According toO ¨ hman, phobic stimuli are analysed by fast and subcortical information-processing routines. These subcortical processes would provide a rough analysis of the stimulus and then initiate an immediate fear response. Consequently, even before the patient becomes fully aware of the phobic stimulus, a fear response is already on its way. This might explain why phobics experience their fears as uncontrollable. In passing, it should be noted that this view accords well with the neurobiological studies of LeDoux. In his animal studies, LeDoux found evidence for a subcortical fear pathway linking the thalamus with the amygdala. This thalamo-amygdala pathway is a quick and dirty transmission route in which the thalamus carries out a crude analysis of the sensory input and then immediately activates the amygdala, which, in turn, generates an emotional response.
According to LeDoux this pathway has adaptive value in that ‘‘the thalamoamygdala system might be especially useful as a processing channel under conditions where rapid responses are required to threatening stimuli. In such situations, it may be more important to respond quickly than to be certain that the stimulus merits a response.’’ Thus, it is conceivable that in the case of specific phobias, learning
experiences or genetic factors affect the thalamo-amygdala pathway in such a way that it becomes oversensitive to certain phobic cues. Interestingly, Fredrikson and associates found in their PET scan study of snake phobics some indications that the thalamus acts as an important relay station for phobic stimulus processing. On the other hand, experimental studies that addressed the O ¨ hman/LeDoux hypothesis in more depth have come up with mixed results.
In order to examine fast processing routines in phobias, O ¨ hman and Soares confronted spider fearful, snake fearful, and control subjects to subliminal presentations (i.e., 30 msec) of spiders, snakes, and neutral pictures while autonomic arousal as indexed by skin conductance responses (SCRs) were measured. The results of this study were in line with the idea that phobics immediately react to degraded phobic stimuli even when these stimuli are blocked from conscious recognition.
That is, spider fearfuls were found to react with heightened SCRs to subliminal spider pictures, snake fearfuls were found to respond with heightened SCRs to subliminal snake pictures, whereas control subjects did not react with specific SCRs to any of the subliminal pictures. However, attempts to cross-validate these findings in severely phobic adults or children have produced disappointing results. In conclusion, then, the O ¨ hman/LeDoux hypothesis awaits further empirical testing