Research articlePosturographic destabilization in eating disorders in female patients exposed to body image related phobic stimuli
Introduction
The maintenance of an upright stance in humans depends on the central integration of vestibular, visual and somatosensory inputs, and on the integrity of the motor efferent neural pathway, which continuously provides postural adjustment to environmental and body position changes. While research has addressed how organic vestibular end-organ diseases, visual, and somatosensory impairment may disrupt postural control and lead to gait and balance disorders, little is known about the interaction between psychological variables and whole body posture disturbance [1], [2], [3].
Various studies have shown a possible link between static postural control and anxiety in normal subjects [4], and in both adults and children affected by psychological distress [5], [6]. Results suggest that anxiety and depression are associated to an abnormal upright stance. This seems to be particularly the case when postural control is tested in environmental conditions presenting a sensory mismatch between the vestibular, somatosensory and visual systems [7]. One of the most common experimental settings used to trigger a visual-vestibular mismatch is quietly standing in front of a full-field moving scene, so that peripheral retinal activation generates a sensation of motion conflicting with the sense of stationariness provided by the labyrinths and the muscular-skeletal and plantar receptors. In such a sensory conflict paradigm, anxiety appears to disrupt the ability of the central nervous system to ignore the misleading visual information, leading to an increased body sway [8]. This seems to apply to an even greater degree in anxious patients, who are known to be particularly dependent on vision for balance maintenance [9]. In addition, the visual destabilization of posture induced by full-field optokinetic stimulation is reinforced by anxiety in patients with peripheral vestibular disorders. In particular, the posturographic body sway area is significantly increased in anxious patients when the optokinetic stimulation is delivered toward the defective labyrinth, suggesting a close balance-anxiety link mediated by manipulation of the visual information in humans [10]. Moreover, the destabilizing effect of anxiety on human postural control seems to mainly affect the central processing of visual information, and appears less prominent in eye-closed conditions [11], [12].
The neuro-anatomical pathway that hypothetically subserves this emotion-balance link has been identified in the neural circuit connecting vestibular nuclei to the parabrachial nucleus and central amygdale, infralimbic cortex and hypothalamus, the latter three structures been strongly involved in the “fear network” processing emotionally charged visual stimuli [13]. The final emotional and behavioural output is mediated by both nucleus tractus solitarii for autonomic responses and by hypothalamic paraventricular nucleus for stress axis activation [14]. In humans several pieces of evidence confirm that the processing of emotional visual stimuli activates limbic areas, such as amygdale and insula, in which isolated lesions are a possible cause of pseudo-vestibular syndrome [15].
Galeazzi et al. [16] explored the links between visual information processing, emotion and posture in a posturographic study of healthy human participants exposed to their own images reflected by a full-length mirror. Increased body sway, as detected by posturography, was directly related to the severity of body-image preoccupations and to trait anxiety. This postural disturbance was interpreted as stemming from the aversion caused by the visual stimulus in participants with greater body dissatisfaction, which disrupts emotional status similarly to the ‘phobic stimulus’ experienced by patients with bulimia nervosa when exposed to their own body image reflected by a mirror [17] or exposed to a thin-ideal image [18].
In order to further investigate the destabilizing effect on posture previously described and to be able to specifically attribute the effects to negative feelings an individual has about their body image, we compared the postural control of patients with an eating disorder diagnosis to that of healthy participants without diagnosable psychiatric disorders when exposed 1) to their own image reflected on a full-length mirror, 2) to their thin-ideal image embodied by a fashion model image reproduced on a frontal full-field screen. We hypothesized that patients with an eating disorders would show higher posturographic destabilization when exposed to these stimuli in comparison to the control group and that destabilization would correlate to body dissatisfaction psychometric measures.
Section snippets
Material and methods
Participants comprised two groups:
- the clinical population, eating disorders group (EDG) was composed of 17 female patients, aged from 18 to 42 consecutively admitted to the Psychiatric Day Hospital Unit of Modena University Hospital (Italy) who were diagnosed with an eating disorder (anorexia nervosa n = 10, bulimia n = 3, eating disorder not otherwise specified n = 4), with diagnosis confirmed according to the Italian Version of the Structured Clinical Interview- DSM-IV (SCID-I) [19] and the Mini
Results
The EDG and the CG groups did not differ significantly in age (EDG mean = 29.9 years old, S.D. = 7.9 vs CG mean 25.9 S.D. = 2.4: t = 2.032, df 33, p=0.05), years of education and marital status, whereas the two groups differed for BMI, the EDG presenting with a BMI which tended to be higher (mean = 25.89, S.D.=11.1) compared to the CG (mean 20.16, S.D. = 2.37; t = −2.14, df 33, p =0.04).
Table 1 reports psychometric and posturographic (ES90) measures in the EDG and CG group and details significant differences.
Discussion
As suggested by a previous study by our group in healthy participants [16], the results reported confirm the hypothesis that body image psychological appraisal is associated to specific posturographic changes when patients with eating disorders are exposed to their own body image reflected by a full-length mirror and to a thin ideal model image, that is, their postural control is forced to a worse condition in response to visual cues that potentially evoke negative feelings and anxiety. In
Conclusions
Our results point at a typical destabilization of posturographic measures for patients with eating disorders when exposed to visual stimuli pertinent to body image satisfaction. On the basis of these promising results gathered from the application of stabilometric investigation in eating disorder population compared to controls, further research is mandated to test the theory in male participants, to explore the specificity of the effect and to evaluate the utility of such posturographic
References (48)
- et al.
Is there a hypersensitive visual alarm system in panic disorder
Psychiatry Res.
(2011) - et al.
Neurological bases for balance-anxiety links
J. Anxiety Disord.
(2001) - et al.
Behavioral models for anxiety and multisensory integration in animals and humans
Prog. Neuropsychopharmacol. Biol. Psychiatry
(2011) - et al.
Anxiety affects the postural sway of the antero-posterior axis in college students
Neurosci. Lett.
(2001) - et al.
Panic disorders: the role of balance system
J. Psychiatr. Res.
(2001) - et al.
Mood states and anxiety influence abilities to maintain balance control in healthy human subjects
Neurosci. Lett.
(2002) - et al.
Visually induced postural sway in anxiety disorders
J. Anxiety Disord.
(2007) - et al.
The effect of anxiety on postural control in humans depends on visual information processing
Neurosci. Lett.
(2004) - et al.
Effect of anxiety on antero-posterior postural stability in patients with dizziness
Neurosci. Lett.
(2011) Neural substrates linking balance control and anxiety
Physiol. Behav.
(2002)