Friday, May 14, 2010

OBSERVATIONAL REPORT: A cerebellar-vestibular explanation for fears/phobias

The vestibular system consists of three semi-circular canals filled with liquid and two "otoliths" that are located in the inner ear. These structure tell us how we are positioned and space and allow us to judge how we are moving through space. Malfunctions of the vestibular system can cause vertigo, nausea, dizziness and inability to balance. Levinson suggests that vestibular disfunction may predispose people to develop many kinds of phobia.

TITLE: A cerebellar-vestibular explanation for fears/phobias: hypothesis and study
AUTHOR: Levinson HN
JOURNAL: Perceptual and Motor Skills. 1989 Feb;68(1):67-84.
"To clarify and test the cerebellar-vestibular (CV) basis of fears/phobias, responses of 4000 learning disabled children, adolescents, and adults with neurological and electronystagmographic (ENG) evidence of CV-dysfunction were analyzed for anxiety-related symptoms. Of this sample, 64.6% indicated fears/phobias; females were significantly more predisposed; mixed-handedness was significantly related to fears of heights and reduced vestibular response or asymmetric vestibular functioning. Also, adults had a higher incidence of the specific fears/phobias characterizing agoraphobia than children and adolescents. Analysis of factors reported as triggering the fears/phobias led to (1) a classification and theory of fears/phobias, obsessions/compulsions, and related anxiety symptoms based on realistic or traumatic, neurotic, and CV- or other CNS-based mechanisms rather than on DSM-III--R surface descriptions; (2) an understanding of the relationships between mitral valve prolapse, agoraphobia and panic episodes, as well as depression; and (3) new insights into differential diagnosis and selective treatment." [full text]

The sample used in this study are not a normal cross-section of the population, but a large group of learning disabled individuals--a group where vestibular problems are more common. And the study does not have a control group which greatly limits the conclusions that can be drawn.

However it is interesting to note that anti-motion sickness medications which help stabilise the vestibular system and improve its function, seemed to help this group with their phobias.

riving anxiety was reported by 4.9% of the adults in the group, and 2% of the overall group (including children and adolescents who are less likely to be driving). The paper assesses phobias and vestibular function but does not seem to (be able to?) assess the correlation between the two and so is ultimately more suggestive than informative. However there does seem to be some grounds for suggesting that vestibular disfunction may be a predisposing factor for developing phobias including driving anxiety.

Thursday, May 13, 2010

EXPERIMENTAL REPORT: Salivary cortisol response during exposure treatment in driving phobics

Whenever a person become alert and ready to react they are experiencing "stress" (all so called the fight-or-flight response). A range of responses occur including physiological stress responses that prepare the body for strenuous activity. The following study measured one aspect of this physiological response, cortisol in saliva. Cortisol (shown right) is released by a part of the adrenal gland and its main function to to increase blood sugar

TITLE: Salivary cortisol response during exposure treatment in driving phobics
AUTHOR: Alpers GW et al
JOURNAL: Psychosomatic Medicine 65:679-687 (2003)
"OBJECTIVE: Extensive research on the hypothalamic-pituitary-adrenal (HPA) axis response to stress has not clarified whether that axis is activated by phobic anxiety. We addressed this issue by measuring cortisol in situational phobics during exposure treatment. METHODS: Salivary cortisol was measured in 11 driving phobics before and during three exposure sessions involving driving on crowded limited-access highways and compared with levels measured in 13 healthy controls before and during two sessions of driving on the same highways. For each subject, data collected in the same time period on a comparison nondriving day served as an individual baseline from which cortisol response scores were calculated. RESULTS: Cortisol levels of driving phobics and controls did not differ on the comparison day. Phobics also had normal cortisol response scores on awakening on the mornings of the exposures but these were already increased 1 hour before coming to the treatment sessions. Phobics had significantly greater cortisol response scores during driving exposure and during quiet sitting periods before and afterward. These greater responses generally paralleled increases in self-reported anxiety. At the first exposure session, effect sizes for differences in cortisol response scores between the two groups were large. Initial exposure to driving in the first session evoked the largest responses. CONCLUSION: The data demonstrate that the HPA axis can be strongly activated by exposure to, and anticipation of, a phobic situation." [abstract and full text]

TAKE HOME MESSAGE: People with a driving phobia suffer measurable physiological stress which starts in anticipation of the driving session and lasts for some time afterwards.


I'm sorry, but anyone suffering from a phobia can feel for themselves the racing heart rate, sweaty palms and all the classic symptoms of a physiological stress response. So even after reading the introduction to this paper (which outlined previous studies that had question the existence of a full stress response as part of phobic anxiety) I am having some trouble seeing this as a matter that was in an serious doubt. Inconsistent results are most likely caused by the fact that accurately measuring cortisol is a relative skilled task. Also cortisol is an good measure or stress experience over the course of minutes or hours, and people experiencing chronic stress might not show normal responses.

Saturday, May 8, 2010

REVIEW ARTICLE: Virtual Reality in Anxiety Disorders by Gorini, A & Riva, G

Virtual reality is a method for exposing phobic drivers to the situations they fear under controlled, interactive and safe conditions. The paper described below explains how virtual reality is used in the treatment of a range of phobias and provides a good background before tackling the more detailed experimental papers relating to the use of virtual reality in treating driving phobia (such as Ward & Taylor, 2000). Free full text of this review article is available online.

TITLE: Virtual reality in anxiety disorders: the past and present
AUTHOR: Gorini, A & Riva, G
JOURNAL: Expert Reviews of Neurotherapeutics, 2008, 8, 215-33.

ABSTRACT: "One of the most effective treatments of anxiety is exposure therapy: a person is exposed to specific feared situations or objects that trigger anxiety. This exposure process may be done through actual exposure, with visualization, by imagination or using virtual reality (VR), that provides users with computer simulated environments with and within which they can interact. VR is made possible by the capability of computers to synthesize a 3D graphical environment from numerical data. Furthermore, because input devices sense the subject's reactions and motions, the computer can modify the synthetic environment accordingly, creating the illusion of interacting with, and thus being immersed within the environment. Starting from 1995, different experimental studies have been conducted in order to investigate the effect of VR exposure in the treatment of subclinical fears and anxiety disorders. This review will discuss their outcome and provide guidelines for the use of VR exposure for the treatment of anxious patients." [PUBMED abstract, Full Text pdf]

This article provides a good overview of the theoretical purpose of virtual reality treatemnt for phobias, the equipment and procedures used, and research to date. There is relatively breif coverage of driving phobia, specifically:

"Driving phobia, defined as a specific phobia, situational type in Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV, is characterized by intense and persistent fear of driving, which increases as a person anticipates or is exposed to driving stimuli. People with driving phobia acknowledge that their fears are excessive or unreasonable, yet are unable to drive, or tolerate driving with considerable distress. The inability to drive results in a major loss of mobility and independence, which interferes with daily activities.

Currently, the only three studies we have found in literature suggest that VRET may be a quite promising intervention for treating driving phobia, but obviously, more controlled trials and follow-up evaluations are necessary to support these preliminary findings"

The studies referred to are:
* Wald J. Efficacy of virtual reality exposure therapy for driving phobia: a multiple
baseline across-subjects design. Behav. Ther. 35, 621–635 (2004).
* Wald J, Taylor S. Efficacy of virtual reality exposure therapy to treat driving phobia: a case report. J. Behav. Ther. Exp. Psychiatry 31(3–4), 249–257 (2000).
* Walshe DG, Lewis EJ, Kim SI, O’Sullivan K, Wiederhold BK. Exploring the use of computer games and virtual reality in exposure therapy for fear of driving following a motor vehicle accident. Cyberpsychol. Behav. 6(3), 329–334 (2003).