Psychosocial stress based on public speech in humans: is there a real life/laboratory setting cross-adaptation?

Abstract

Repeated or chronic exposure to stressors is associated with changes in neuroendocrine responses depending on the type, intensity, number and frequency of stress exposure as well as previous stress experience. The aim of the study was to test the hypothesis that salivary cortisol and cardiovascular responses to real-life psychosocial stressors related to public performance can cross-adapt with responses to psychosocial stress induced by public speech under laboratory setting. The sample consisted of 22 healthy male volunteers, which were either actors, more precisely students of dramatic arts or non-actors, students of other fields. The stress task consisted of 15 min anticipatory preparation phase and 15 min of public speech on an emotionally charged topic. The actors, who were accustomed to public speaking, responded with a rise in salivary cortisol as well as blood pressure to laboratory public speech. The values of salivary cortisol, systolic blood pressure and state anxiety were lower in actors compared to non-actors. Unlike non-actors, subjects with experience in public speaking did not show stress-induced rise in the heart rate. Evaluation of personality traits revealed that actors scored significantly higher in extraversion than the subjects in the non-actor group. In conclusion, neuroendocrine responses to real-life stressors in actors can partially cross-adapt with responses to psychosocial stress under laboratory setting. The most evident adaptation was at the level of heart rate responses. The public speech tasks may be of help in evaluation of the ability to cope with stress in real life in artists by simple laboratory testing.

Keywords:

• Actors
• adaptation
• anxiety
• blood pressure
• cortisol
• heart rate
• public speaking

Introduction

Acute and chronic stress stimuli, which are negatively influencing the quality of human life (Herman et al., 2015; Tafet & Nemeroff, 2016) are mainly mental in origin. Somatic stressors are inducing appropriate neuroendocrine activation also under laboratory settings, allowing thus evaluation of potential pathophysiological consequences and regulatory mechanisms involved. However, laboratory mental stress tasks result in sympathetic-adrenomedullary activation without clear impact on the hypothalamic-pituitary-adrenocortical (HPA) axis (Garafova et al., 2014; Jezova et al., 2002). Exceptions are stress tests based on public speech. Psychosocial stress related to tasks which involve standing and speaking in front of an unknown audience are certainly stressful enough to induce broad neuroendocrine responses including huge activation of the HPA axis (Jezova et al., 2004; Kirschbaum et al., 1993).

In general, repeated or chronic exposure to stressors is associated with changes in neuroendocrine responses depending on the type of the stressor, its intensity, number and frequency of exposure as well as previous stress experience. Most often we see the development of adaptation or habituation to the sustained or repeated stressor with decreased responses of several, though not all, hormonal systems (Belda et al., 2015; Chauhan et al., 2015). A hyper-responsiveness, particularly to a novel stressor, may also develop (Aguilera, 1994; Sabban & Serova, 2007).

With respect to psychosocial stress in humans under laboratory setting, studies using repeated exposure to Trier social stress test showed clear habituation of HPA responses. On the other hand, the sympathetic nervous system showed rather uniform activation patterns even with repeated exposure to mentioned psychosocial challenge (Schommer et al., 2003).

Relatively little work has been done on neuroendocrine responses to repeated “naturalistic” stressors involving public speech or other performance in front of unknown audience. We have shown previously signs of adaptation in musicians. In a group of professional musicians, the concentrations of salivary cortisol did not rise during their public artistic performance. Only soloists of the orchestra exhibited increases in salivary cortisol (Jezova et al., 1992). A recent study, again on live music performance in singers, demonstrated that salivary cortisol concentrations increased during a live concert, while decreased during singing without audience (Fancourt et al., 2015).

The aim of the present study was to test the hypothesis that the neuroendocrine responses to real-life psychosocial stressors related to public performance can cross-adapt with responses to psychosocial stress induced by public speech under laboratory setting. To do so we have investigated the responses to laboratory public speech task in a group of actors, more precisely students of dramatic arts or marionette play, compared to the responses of non-actors. If the hypothesis is confirmed it would allow evaluation of the ability to cope with stress in real life in artists by simple laboratory testing.

Methods

Subjects

The sample consisted of 22 healthy male volunteers in the age of 19–25 years with body mass index (BMI) 20–25 and baseline systolic blood pressure in a sitting position less than 140/90 mmHg. Out of them, eight subjects were students of the Academy of Performing Arts Bratislava (actors) and the rest were students of other universities (non-actors). Their mental and physical health was determined by a psychiatric interview, medical history and blood pressure measurements. Subjects were excluded from the study if they were suffering from any somatic or mental diseases, had family history of psychiatric disorders or were taking any medication. The subjects gave written informed consent to participate. The study was performed in accordance with the Declaration of Helsinki. The protocol was approved by the Ethical Committee of the Slovak Academy of Sciences, Bratislava, Slovakia.

Stress procedure and study design

A public speech task described previously (Jezova et al., 2004) was used as the psychosocial stress procedure. The tests were performed in the early afternoon after 3 h of fasting. Upon arrival, each subject was seated in a waiting room adjacent to the testing room and was asked to complete psychological questionnaires. Approximately half an hour after arrival, physiological measurements and saliva samples for basal values were taken and the stress procedure was started. The stress procedure consisted of 15 min of preparation, when the subject was asked to prepare a speech on an emotionally charged topic, followed by the speech for 15 min in front of a jury of four to five members. During the speech, the subject was standing on a small stand and illuminated by bright light. The performance was recorded by a video camera and observed by. Physiological measurements and saliva samples for stress and post-stress values were taken at the end of the preparation (time 15 min) and speech (time 30 min) periods, and 15 (time 45 min) or 30 (time 60 min) after the speech. During the time periods after the speech, subjects remained in a sitting position completing questionnaires and reading magazines.

Measurements

Measurements of blood pressure and heart rate were performed by an automatic blood pressure measuring device (Dinamap, Criticon, Tampa, FL). Saliva samples were collected in sterile salivettes (Sarstedt, Leicester, UK), which were capped and frozen at 20 °C until analyzed. Salivary cortisol concentrations were measured by radioimmunoassay as described previously (Jezova et al., 2002).

Slovak version of the State Trait Anxiety Inventory (STAI) was used for the evaluation of state and trait anxiety as described previously (Jezova et al., 2013). The questionnaire consists of two subscales specifically examining the state (STAI-X1) and trait anxiety (STAI-X2) dimensions. “Big five” inventory was used to identify the following personality traits: neuroticism, extraversion, openness, agreeableness, and conscientiousness. Next, Dopen questionnaire for psychoticism, extraversion, neuroticism and lies was used.

Statistics

Due to having a small sample size, data were screened for outliers and assessed for the normality of distributions. There were no outliers and both kurtosis and skewness test indicated normal distribution. The normal distribution was confirmed also by Shapiro–Wilk test. Under these conditions, even a small sample (n = 20) may be analyzed by parametric tests (Wilcox, 2010). Analysis of variance (ANOVA) for repeated measures with group (actors versus non-actors) as the between-subjects factor and time as the within-subjects factor was used to evaluate changes in cardiovascular parameters, cortisol and state anxiety score. Whenever interaction reached significance, Tukey’s post hoc test was performed. Scores of psychological variables and increments were evaluated by t-test for independent groups. Results are expressed as means ± SEM. The overall level of statistical significance was defined as p < 0.05.

Results

ANOVA for repeated measures revealed a significant main effect of group (F_{(1, 19)} = 9.66, p < 0.05) and time (F_{(3, 57)} = 19.33, p < 0.001) on salivary cortisol concentrations (Figure 1(A)). Psychosocial stress procedure led to a significant rise in salivary cortisol concentrations and they were lower in the group of actors. Maximal increments in salivary cortisol concentrations in response to stress task were similar in actors and non-actors (Figure 1(A)).

Figure 1. Changes in salivary cortisol concentrations (A) and the heart rate (B) during the stress procedure in group of actors and non-actors. Statistical significance as revealed by ANOVA for repeated measures with subsequent Tukey post hoc test: ^XXX(p < 0.001) for both groups: for time points 45 min and 60 min versus 0 min and 30 min; ***(p < 0.001) for non-actors group: 30 min versus 0 min, 15 min and 45 min; #(p < 0.05) for time point non-actors versus actors. Inset, maximal increments of salivary cortisol concentrations (A) and the heart rate (B) in group of actors and non-actors. Statistical significance as revealed by t-test for independent group: **(p < 0.01). Data are expressed as means ± SEM.

Repeated measures ANOVA showed a significant main effect of time (F_{(3, 60)} = 8.32, p < 0.005) and significant time by group interaction (F_{(3, 60)} = 3.97, p < 0.05) on the heart rate (Figure 1(B)). Post hoc comparisons showed that psychosocial stress procedure resulted in a significant rise in the heart rate at time 30 min compared to 0 min (p < 0.001), 15 min (p < 0.001) and 45 min (p < 0.001) in non-actors only. No changes in the heart rate were observed in the group of actors. Statistical analysis revealed that maximal increment in the heart rate (Figure 1(B)) was significantly higher in non-actors compared to actors (t₂₀ = −3.00, p < 0.01).

As revealed by repeated measures ANOVA for factor time, psychosocial stress procedure resulted in a significant rise in systolic (F_{(3, 60)} = 32.66, p < 0.001) and diastolic blood pressure (F_{(3, 60)} = 32.66, p < 0.001) (Figure 2). Systolic blood pressure increased significantly at time 15 min and 30 min compared to time 0 min (p < 0.001, p < 0.001, respectively) and 45 min (p < 0.001, p < 0.001 respectively). Diastolic blood pressure was significantly higher at time 30 min compared to time 0 min (p < 0.001), 15 min (p < 0.001) and 45 min (p < 0.001). There was a significant main effect of group on systolic blood pressure (F_{(1, 20)} = 5.00, p < 0.05) showing that actors exhibited decreased systolic blood pressure throughout the procedure. Diastolic blood pressure was not different between the groups. No interaction between factors was observed. Statistical analysis of maximal increments in systolic and diastolic blood pressures (Figure 2) by t-test for independent groups did not reveal any significant differences between actors and non-actors.

Figure 2. Changes in systolic (A) and diastolic (B) blood pressure during the stress procedure in group of actors and non-actors. Statistical significance as revealed by ANOVA for repeated measures with subsequent Tukey post hoc test: ***(p < 0.001) for both groups: for time points 15 min and/or 30 min versus 0 min and 45; Inset, maximal increments of systolic (A) and diastolic (B) blood pressure in group of actors and non-actors. Data are expressed as means ± SEM.

Repeated measures ANOVA of data on state anxiety (Figure 3) revealed a significant main effect of group (F_{(1, 19)} = 74.01, p < 0.001) indicating that actors exhibited lower state anxiety compared to non-actors. No significant main effect of time or interaction between the factors was found. The increment in state anxiety score was similar in both the groups (Figure 3).

Figure 3. State anxiety level before and after the stress procedure in group of actors and non-actors. Statistical significance as revealed by ANOVA for repeated measures. Inset, increment in state anxiety score in group of actors and non-actors. Data are expressed as means ± SEM.

As revealed by t-test for independent groups, no significant differences between actors and non-actors were observed in trait anxiety. Evaluation of personality inventories revealed significantly higher extraversion in actors compared to non-actors by both questionnaire Dopen (t₂₀= 3.94, p < 0.001; actors: 22.0 ± 1.25 versus non-actors: 15.8 ± 0.94) and “Big five” inventory (t₂₀=17.98, p < 0.05; actors: 45.6 ± 2.05 versus non-actors: 38.7 ± 1.55). No significant differences in other personality traits between the groups were identified.

Discussion

Although a small number of participants were investigated, the present study shows that subjects, who are accustomed to speaking in front of an unknown audience, respond with a significant rise in salivary cortisol as well as blood pressure to public speech performed under laboratory setting. In comparison to inexperienced persons, the values of salivary cortisol concentrations, systolic blood pressure and state anxiety were lower in the actor group. Unlike non-actors, subjects with experience in public speaking did not show stress-induced rise in the heart rate.

Though present, the neuroendocrine response to psychosocial stress associated with laboratory public speech test was lower in actors compared to non-actors. This finding reflects certain degree of adaptation. Repeated exposure to stressors may lead to signs of habituation with lower neuroendocrine activation but also to a hyperresponiveness. Such phenomena are well recognized in animal studies. With respect to the HPA axis, strong evidence exists on habituation to the same, homotypic stressor and on facilitation of the response to a novel, heterotypic stressor (Aguilera, 1994). In addition, the phenomenon “cross-adaptation” has also been described and it means reduced stress responsiveness to a novel stressor in previously stress adapted organisms (Belda et al., 2015; Chauhan et al., 2015). In support of the cross-stressor adaptation hypothesis are the results of a human study showing that 12-week exercise training reduced stress reactivity to Trier social stress test in salivary cortisol and the heart rate (Klaperski et al., 2014). The results of the present study are consistent with the latter report, although it is not easy to say whether in evaluating actors and non-actors we are dealing with adaptation or cross-stressor adaptation. Psychosocial stress experienced in the professional lives of actors is similar but not identical with the psychosocial stress induced by public speech under laboratory conditions.

Interestingly, the stress-induced rise in diastolic blood pressure was unchanged and the rise in systolic blood pressure was only slightly lower in actors compared to non-actors. Neither repeated public speaking tasks under laboratory setting led to reduction of systolic blood pressure (Al'Absi et al., 1997). Adaptation processes of individual components of the sympathetic-adrenomedullary system are not always parallel to those of the HPA axis (Sabban & Serova, 2007). It is known for a long time that the habituation of the HPA axis is usually accompanied by lower responses of plasma epinephrine but not norepinephrine. After repeated handling in rats, for example, a reduction of plasma epinephrine and adrenocorticotropic hormone levels was observed, while norepinephrine levels increased to the same extent as after the first handling (Dobrakovová et al., 1993). The dissociation between HPA axis and sympathetic-adrenomedullary system response patterns during psychosocial stress was observed also in humans. Schommer et al. (2003) investigated Trier social stress test and they reported a quick habituation of HPA but sustained sympathetic nervous system responses over the three repeated stress sessions.

In contrast to the significant rise in the heart rate at the end of the stress procedure in non-actors, laboratory public speech failed to increase the heart rate in the group of actors. In previous studies using public speaking (Al'Absi et al., 1997; Schommer et al., 2003) only slight reduction of the heart rate was observed following three repetitions of the task. The absence of the rise in heart rate in actors accustomed to public speaking may be related to lower level of stress perception, which was not directly measured but is supported by lower state anxiety of actors compared to non-actors. Higher perception of stressors, even though of a different type, was related to reduced parasympathetic activity (Clays et al., 2011). It may be suggested that enhanced activation of the parasympathetic nervous system could contribute to the reduction of stress-induced tachycardia in actors. It is likely that there is a dissociation between sympatho-adrenal and sympatho-neural responses. Present results underline the importance of adrenomedullary activation during public speaking. As expected, evaluation of personality traits revealed that actors, i.e. students of dramatic arts, scored higher in extraversion than the subjects in the control group. In the literature available, the assessments of personality traits were focused on creativity, talent and type of the art. For example, lower scores in extraversion and higher scores in neuroticism were described in students of visual arts (Burch et al., 2006).

Conclusions

The neuroendocrine responses to real-life psychosocial stressors related to public performance can partially cross-adapt with responses to psychosocial stress induced by public speech under laboratory setting. The most evident adaptation was at the level of heart rate responses. The public speech tasks may be of help in the evaluation of the ability to cope with stress in real life in the artists by simple laboratory testing.

Funding information

The study was supported by the grant of APVV-0496-12 and FG28/2015.

Disclosure statement

The authors do not have any financial interest or any other conflict of interests.