Patient Care Neurology & Psychiatry - November 2007 - (Page 21)

PHOBIAS Community surveys show that most people who have specific phobias do not present for treatment. Those who do are more likely to fear commonly encountered situations (pets, elevators, transportation), to have multiple phobias, and to experience panic attacks in the context of their phobias. Untreated individuals are more likely to have a single phobia, especially of the blood-injuryinjection type, and are unlikely to experience panic attacks.7 Specific phobias display broad variability in their impact on mobility and quality of life. Someone with a snake phobia may be able to arrange daily life to preclude virtually all potential exposures. In contrast, severe phobias related to heights, transportation, pets, or insects may significantly hamper mobility and social or employment possibilities. Dental phobia or blood-injury-injection phobia may lead to avoidance of needed health care with its attendant complications. Poor diabetic control has been reported among diabetics with blood-injury-injection phobia.8 Etiology Understanding of phobias has traditionally been based on fear-conditioning models. From this vantage, a phobia develops when a person, consciously or not, associates marked anxiety or panic with a specific trigger.9 Less often, phobias may be acquired vicariously by observation of the fearful behavior of others or by very salient misinformation received from others.9 All components of the fear-conditioning process in humans demonstrate moderate heritability (35% to 45%).10 Reported heritability estimates include 46% for situational phobias, 47% for animal phobias, and 59% for blood-injury-injection phobias.11 Twin studies are compatible with genetic models, which postulate that the vulnerability to phobias is largely innate and does not arise directly from environmental experiences.12 From this viewpoint, phobias reflect genetically determined exaggerated fear and/or disgust responses to evolutionary, survivalrelevant cues or a genetic deficiency in adaptation to such cues. Differences in temperament (eg, neuroticism, introversion, behavioral inhibition, anxiety sensitivity) have been linked with vulnerability to fear conditioning. Identified brain substrates may underlie such individual differences; for example, thickness of the ventromedial prefrontal cortex may explain individual differences in fear modulation.13 Carriers of the short allele of the serotonin transporter show stronger amygdala reactivity both to frightening stimuli and to stressful, uncertain stimuli.14 Although the traditional stress-diathesis model usually does not apply to specific phobias, it has IMAGE: SINDI PRICE NOVEMBER 2007 PATIENT CARE NEUROLOGY & PSYCHIATRY 21

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Patient Care Neurology & Psychiatry - November 2007 Contents Research Digest Medicine in the News The 15-Minute Visit Dementia workup and treatment: Do the drugs really work? Help for Your Patients Who Suffer from Specific Phobias Clinical Clips Case & Comment The Science of Healing Classified Advertising

Patient Care Neurology & Psychiatry - November 2007

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