The comparative study of salivary alpha-amylase and salivary cortisol reaction to electric stimulation in avoidant personality disorder

Background : Avoidant personality disorder (AvPD) is a personality disorder recognized in the Diagnostic and Statistical Manual of Mental Disorders handbook (DSM-IV TR) in a person characterized by a pervasive pattern of social inhibition, feelings of inadequacy, extreme sensitivity to negative evaluation, and avoidance of social interaction. To this day, the causes of AvPD are not clearly defined, and may be influenced by a combination of social, genetic, and psychological factors. The disorder may be related to temperamental factors that are inherited. Moreover, the disorder may be related to the dysfunction of stress response systems. A role for hypothalamic-pituitary-adrenal (HPA)-axis activity in mediating stress responses has been intensively investigated for decades. Cortisol is an essential hormone in the regulation of stress response in the HPA axis, and salivary cortisol (sC) has been used as a simple, noninvasive index of free circulating cortisol levels. Recently, salivary alpha-amylase (sAA) has emerged as a new biomarker for responses to psychosocial stress within the sympathetic adrenomedullary (SAM) systems. To evaluate the effects of physical stress on HPA and SAM systems, we assessed the secretion of sAA and sC in AvPD patients and healthy volunteers after exposure to electric stimulation stress. Methods : Eleven AvPD patients with no psychiatric comorbidity (7 males and 4 females, aged 25.2±4.4) and 126 healthy volunteers with no history of psychiatric disorder (56 males and 70 females, aged 25.9±4.5) participated in this study. All subjects were exposed to electric stimulation stress with the stimulator coil on their wrists. Subjects were stimulated in incremental steps until they reached their threshold stimulus, defined as the greatest stimulus they could tolerate. The greatest stimulus lasted 40 seconds. To examine sAA and sC stress responses, we measured sAA and sC levels three times immediately before, immediately after, and 20 min after the intervention. We also determined State-Trait anxiety Inventory (STAI) scores and Profile of Mood State (POMS) scores of all subjects before the intervention. This study was approved by the Ethics Committee of Oita University. Written informed consent was obtained from all participants. Results : A significant sAA response to electric stimulation was found with peak values registered immediately after interventions in AvPD patients. However, we found no significant sAA response to electric stimulation in healthy controls. Moreover, AvPD patients always showed significantly higher sAA levels than healthy controls immediately before, immediately after, 20 min after the intervention. However, there was no significant difference in sC reactions between AvPD patients and healthy controls, and we found no significant sC response to electric stimulation in each group. The age, the proportion of males to females and the mean strength of electric stimulation in each group were statistically equal. STAI-Trait and STAI-State scores of AvPD patients were both greater than those of healthy controls. And POMS scores also showed greater subscales of tension-anxiety, depression, fatigue, confusion in AvPD patients than those of healthy patients. Conclusion : These preliminary results suggest that AvPD patients may be easily suffered from stronger feelings of tension-anxiety, depression, fatigue, and confusion compared to healthy people in stressful situation. Moreover, AvPD patients may react to stressors with SAM systems predominantly. The above indicates that the excessive acceleration of sympathetic nerves system may be related to the pathology of AvPD

Correlation between salivary cortisol AUCi and electrical current in females or males.

<p>Correlation between salivary cortisol AUCi and strength of applied electrical current in females (n = 93) (A). Correlation between salivary cortisol AUCi and strength of applied electrical current in males (n = 56) (B).</p

Correlation between sAA, salivary cortisol AUCi and electrical current.

<p>Correlation between sAA AUCi and strength of applied electrical current (A). Correlation between salivary cortisol AUCi and strength of applied electrical current (B).</p

Characteristics of electrical stimulation and TSST.

<p>Spearman's rank correlation coefficients were used to statistically compare the linear correlations between two tests (electric stimulation and TSST). p-value <0.05 were indicated in bold.</p

Relationship between sAA, TSST and electrical stimulation.

<p>Relationship of basal sAA levels (A), sAA levels after electrical stimulation (B) and sAA levels 20 min after electrical stimulation (C) between TSST and electrical stimulation exposure.</p