- Email: [email protected]
Psychophysiological correlates of anxiety: A single-case study
Anxiety Disorders 20 (2006) 829–835
Psychophysiological correlates of anxiety: A single-case study Laura E. Lewis *, Robert F. Drewett Department of Psychology, University of Durham, Durham, DH1 3LE, UK Received 26 April 2005; received in revised form 20 May 2005; accepted 31 August 2005
Abstract We examined the relationship between self-reported anxiety and physiological measures (blood pressure and heart rate) in a series of exposures to a feared situation of a single participant with panic disorder with agoraphobia. During each exposure, readings of heart rate, systolic blood pressure and diastolic blood pressure were taken every 20 s. Over 30 exposures, we found a near-linear relationship between anxiety and the three physiological measures. Implications of this result for usefulness of physiological measures in anxiety research and in the clinical treatment of anxiety disorders are discussed. # 2005 Elsevier Ltd. All rights reserved. Keywords: Anxiety; Psychophysiological; Assessment; Exposure; Heart rate; Blood pressure
1. Introduction Anxiety assessments in research and clinical work are predominantly derived from retrospective self-reports. Problems with exclusive use of self-report in the measurement of anxiety have led a number of authors to advocate the utility of physiological measures of anxiety (Nelson & Hayes, 1981; Orr & Roth, 2001; Rachman & Hodgson, 1974; Turpin, 1991; Wilhelm & Roth, 2001). Physiological measures are recommended because they are objective and, with advances in ambulatory techniques, they can be used continuously in real-world settings * Corresponding author at: Flat 28, Springfield House, 5 Tyssen Street, Dalston E8 2LY, UK. Tel.: +44 7862717266. E-mail address: [email protected] (L.E. Lewis). 0887-6185/$ – see front matter # 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.janxdis.2005.08.005
830
L.E. Lewis, R.F. Drewett / Anxiety Disorders 20 (2006) 829–835
(Nelson & Hayes, 1981). Lang’s (1978) three-systems approach to anxiety has provided both a structure and further rationale for inclusion of physiological measures in anxiety assessment. He argued that anxiety is manifest in three independent modes of response: cognitive, behavioral, and physiological. In this view, to emphasize one emotional response system to the exclusion of others neglects important aspects of anxiety. To justify use of physiological measures in research activity and clinical work, psychophysiological research seeks to establish a covariation between self-report and physiological measures of anxiety. Where a moderate covariation is known to exist, physiological assessment methods can be used with confidence to quantify anxiety symptoms objectively. In clinical work, the discrepancies between the two domains of response in the context of this covariation can facilitate the formulation of therapeutic intervention (Rachman & Hodgson, 1974). Most psychophysiological research investigating the link between anxiety and physiology has been conducted in the laboratory where it is easier to monitor and induce anxiety with a minimum of confounding variables. The often-cited concern about this laboratory research is its ecological validity and the generalizability of artificially inducing anxiety in an unnatural environment (Bystrisky & Shapiro, 1992; Whittal & Goetsch, 1995; Wilhelm & Roth, 2001). When anxiety is measured as it occurs naturally in a real-life setting, it is more representative of that experienced by individuals in their day to day lives (Bystritsky, Craeske, Maidenberg, & Shapiro, 1995; Wilhelm & Roth, 1999). Results from the handful of published studies of naturally occurring anxiety demonstrate that the majority of panic attacks are accompanied by elevations in physiological measures (Bystritsky et al., 1995; Freedman, Ianni, Ettedgui, & Puthezhath, 1985; Gaffney, Fenton, Lane, & Lake, 1988; Khawaja & Oei, 1999; Margraf, Taylor, Ehlers, Roth, & Agras, 1987; Shear et al., 1987; Taylor et al., 1986; Wilhelm & Roth, 1999). On the other hand, almost all the studies found that a certain proportion of the panic attacks that was monitored occurred without significant change in physiological measures. Gaffney and his colleagues (1988) found that 17 out of 31 naturally occurring panic attacks in panic patients were not associated with increased heart rates. In addition, none of these studies establishes a systematic covariation between anxiety states and physiological responses. One reason for this is that recordings were often made semicontinuously. Bystritsky and his colleagues (1995) monitored physiological responses of ten patients with panic disorder and 10 matched control subjects during regular daily activity. The ambulatory recorder was set to take recordings between two and five times an hour with the result that the patterns of change in heart rate and blood pressure from nonpanic to panic trials were inconsistent. Another problem with the methodology of previous naturalistic studies was that patients were not supervised when they recorded their anxiety feelings. Khawaja and Oei (1999) examined the psychophysiological correlates of anxiety semicontinuously in six panic disorder patients’ feared situations. The participants recorded when they started feeling anxious and how they were feeling every minute during the exposure. Heart rate
L.E. Lewis, R.F. Drewett / Anxiety Disorders 20 (2006) 829–835
831
data showed very little pattern of increase associated with self-reported anxiety. An important disadvantage of this study was that distress levels were not consistently reported by the participants during the panic attacks. Wilhelm and Roth’s (1999) study of anxiety in vivo demonstrates how ambulatory recording techniques can reliably be used to measure physiological responses in the natural environment. They carried out an assessment of selfreported anxiety and physiological measures during a 12-min flight in 14 people each meeting DSM-III-R criteria for simple flying phobia (American Psychiatric Association, 1987) and 15 controls matched for age and sex to the experimental group. Tested individually, the participants were linked to a multichannel monitoring device, which recorded changes in cardiovascular, electrodermal and respiratory activity. They were requested to rate their anxiety, tension, desire to leave and excitement on Subjective Units of Distress (SUD) scales from 0 to 10 at the end of preflight baseline, 3 min after take-off and at the end of postflight baseline. At these times, subjects were also requested to fill out questionnaires asking them ‘‘how they feel right now’’ and the 20-item STAI-State questionnaire (Spielberger, Gorsuch, & Luchene, 1970). Results showed that a 97% correct classification of subjects into anxious and nonanxious groups could be achieved using either the physiological or self-report measures. However, there were insufficient concomitant data to establish a correlation between self-reported anxiety and physiological measures of anxiety. In the present study, we aimed to examine the relationship between selfreported anxiety and physiological measures of anxiety in a single person with panic disorder with agoraphobia over multiple exposures to his feared situation. The opportunity to do so arose out of the participant’s desire to alleviate himself of a fear of chairlifts through habituation. He lived in a ski-resort and his work regularly took him on chairlifts. He agreed to accompany the first author on three different lifts, each triggering a different degree of anxiety, over a period of nine days on as many occasions as was practically feasible within his working schedule.
2. Method The participant of the study was a 51-year-old male who met DSM-IV criteria for panic disorder with agoraphobia (American Psychiatric Association, 1994). In addition to experiencing unexpected panic attacks in a variety of situations, he specifically feared travelling on a chairlift. Over 9 days, the participant took a total of 30 trips on chairlifts in three different locations, in which he reported varying degrees of anxiety (eight trips at location 0, the least feared, 15 at location 1, intermediate, and 7 at location 2, the most feared). A single trip lasted about 15 min. The first author accompanied the participant, and collected readings of blood pressure, heart rate, and anxiety every 20 s. Systolic blood pressure, diastolic blood pressure and heart rate were
832
L.E. Lewis, R.F. Drewett / Anxiety Disorders 20 (2006) 829–835
measured using an Omron MX3 blood pressure monitor strapped to the participant’s arm. Anxiety was assessed using the SUD scale (Wolpe, 1969), a self-report scale from 0 (not at all anxious) to 10 (the most anxious I could feel). The first author asked the participant to report his level of anxiety on a scale from 0 to 10 every 20 s concurrently with the cardiovascular recordings. The participant did not eat or exercise for an hour before each trip and, following a brief walk to the mountain lift, rested for 5 min before the start of the trip. In the chairlift the participant sat still and quietly with his arm flexed resting on a support at heart level.
3. Results Table 1 shows summary statistics for each variable at each location. Subjective units of distress (SUD) were considerably higher in location 1 than location 0, and higher still in location 2, with each of the physiological measures showing a corresponding pattern. The three physiological variables were highly correlated. The correlation (Pearson’s r) of diastolic and systolic blood pressure was .704, and their correlations with heart rate were .814 and .586, respectively. Fig. 1 shows the relationship between systolic blood pressure and subjective units of distress (SUD), pooled over the 30 trips. The correlation with SUD is .897 for systolic blood pressure. For diastolic blood pressure and for heart rate the corresponding correlations are .657 and .874, respectively. These relationships are monotonic and close to linear. The linear regression for systolic blood pressure is yˆ = 124 + 4.1 (SUD) where yˆ is the estimated value of systolic blood pressure in Table 1 Systolic and diastolic blood pressure, heart rate and subjective units of distress in the three different locations Location
Systolic blood pressure (mmHg)
Diastolic blood pressure (mmHg)
Heart rate (bmp)
Subjective units of distress
Mean N S.D.
129.58 250 6.07
91.37 250 4.46
77.64 250 2.73
1.50 250 1.29
Mean N S.D.
140.91 309 5.08
95.81 309 5.02
88.42 309 5.31
4.22 309 0.81
Mean N S.D.
148.21 283 4.65
100.09 283 5.43
98.39 283 5.33
5.87 283 0.90
0
1
2
N is the number of observations in each location.
L.E. Lewis, R.F. Drewett / Anxiety Disorders 20 (2006) 829–835
833
Fig. 1. Relationship between systolic blood pressure and subjective units of distress. The data are pooled over the three locations.
mm Hg and SUD is the integer value of subjective units of distress. For the other two variables the linear regressions are yˆ = 88.1 + 2.0 (SUD) for diastolic blood pressure and yˆ = 72 + 4.1 (SUD) for heart rate in beats per minute.
4. Discussion Pooled over 30 trips, the relationship between anxiety measured as SUD and systolic blood pressure was monotonic and linear (r = .897). Its relationships with diastolic blood pressure and heart rate were monotonic and close to linear, with r = 0.657 and 0.874, respectively. These strong correlations suggest that the participant’s anxiety comprised psychological and physiological changes that were concurrent and proportional. Present results show a systematic covariation between anxiety and physiological measures, demonstrating that physiological measures can reliably reflect anxiety states outside the laboratory. This adds weight to the argument that ambulatory assessment techniques have potential utility in research and clinical domains. To make plain this potential, Turpin (1991) identifies a number of ways in which anxiety research has benefited from the inclusion of psychophysiological assessment techniques. The study of the processes said to underlie the relationship between anxiety and behavior has relied upon the use of physiological measures (Bernstein, Borkovec, & Coles, 1986). In the field of psychiatric diagnosis and classification, phobic disorders have been differentiated by their psychophysiological correlates.
834
L.E. Lewis, R.F. Drewett / Anxiety Disorders 20 (2006) 829–835
The clinical utility of physiological measures is emphasized by a number of authors (Rachman & Hodgson, 1974; Turpin, 1991; Orr & Roth, 2001; Wilhelm & Roth, 2001). Physiological assessment methods can be used to quantify anxiety symptoms in the initial assessment of the problem and to monitor treatment success in terms of the reversal of physiological symptoms (Wilhelm & Roth, 2001). Where a moderate covariation is known to exist, discrepancies between the two domains of response can be used to facilitate the formulation of therapeutic intervention (Rachman & Hodgson, 1974). For instance, physiological measures can expose some degree of anxiety in individuals who are motivated to appear well-adjusted and misreport their true level of anxiety. The reverse pattern, in which an individual is highly anxious without showing much sign of physiological activation, may be an indication of a reduced threshold for symptom reporting. These discrepancies can throw light on a patient’s particular problem and can refine the choice of treatment for them. There are two principal limitations to this study. First, generalizability of the findings is limited given the use of a single participant. Second, the type of exposure employed in the study (sitting on a chair-lift) limits their clinical relevance. However, it should be possible to replicate the design of the study with other participants in situations which may be considered more clinically relevant using a broader range of physiological indices (e.g., electrodermal and respiratory responses). A series of such studies using the single-case approach across a variety of participants and in a range of clinically relevant settings may help to provide a better understanding of the relationship between self-reported anxiety and physiological measures.
Acknowledgement We thank the participant in this study for providing the original impetus for the research and for his brave cooperation throughout.
References American Psychiatric Association. (1987). Diagnostic and statistical manual of mental disorders (3rd ed., Rev.). Washington, DC: Author. American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington, DC: Author. Bernstein, D. A., Borkovec, T. D., & Coles, M. G. H. (1986). Assessment of anxiety. In: A. R. Ciminero, K. S. Calhoun, & H. E. Adams (Eds.), Handbook of behavioral assessment (pp. 353– 403). New York: Wiley. Bystrisky, A., & Shapiro, D. (1992). Continuous physiological changes and subjective reports in panic patients: a preliminary methodological report. Biological Psychiatry, 32, 766–777. Bystritsky, A., Craeske, M., Maidenberg, T. V., & Shapiro, D. (1995). Ambulatory monitoring of panic patients during regular activity: a preliminary report. Biological Psychiatry, 38, 684–689.
L.E. Lewis, R.F. Drewett / Anxiety Disorders 20 (2006) 829–835
835
Freedman, R. R., Ianni, E., Ettedgui, E., & Puthezhath, N. (1985). Ambulatory monitoring of panic disorder. Archives of General Psychiatry, 42, 244–248. Gaffney, F. A., Fenton, B. J., Lane, L. D., & Lake, C. (1988). Hemodynamic, ventilatory, and biochemical response of panic patients and normal controls with sodium lactate infusion and spontaneous panic attacks. Archives of General Psychiatry, 45, 53–60. Khawaja, N. G., & Oei, T. P. S. (1999). The psychobiological correlates of panic attacks during in vivo exposure. Behavioural and Cognitive Psychotherapy, 27, 353–367. Lang, P. J. (1978). Anxiety: toward a psychophysiological definition. In: H. S. Akiskal, & W. H. Webb (Eds.), Psychiatric diagnosis: exploration of biological Predictors (pp. 365–389). New York: Spectrum. Margraf, J., Taylor, C. B., Ehlers, A., Roth, W. T., & Agras, W. S. (1987). Panic attacks in the natural environment. Journal of Nervous and Mental Disease, 175, 558–565. Nelson, R. O., & Hayes, S. C. (1981). Theoretical explanations for reactivity in self-monitoring. Behavior Modification, 5, 3–14. Orr, S. P., & Roth, W. T. (2001). Psychophysiological assessment: clinical applications for PTSD. Journal of Affective Disorders, 61, 225–240. Rachman, S., & Hodgson, R. (1974). Desynchrony in measures of fear. Behaviour Research and Therapy, 12, 319–326. Shear, M. K., Kligfield, P., Harshfield, G., Devereux, R. B., Polan, J. J., Mann, J. J., et al. (1987). Cardiac rate and rhythm in panic patients. American Journal of Psychiatry, 144, 633–637. Spielberger, C. D., Gorsuch, R. L., & Luchene, R. E. (1970). State-trait anxiety inventory. Palo Alto: Consulting Psychology Press. Taylor, C. B., Sheikh, J., Agras, W. S., Roth, W. T., Margraf, J., Ehlers, A., et al. (1986). Ambulatory heart rate changes in patients with panic attacks. American Journal of Psychiatry, 143, 478–482. Turpin, G. (1991). The psychophysiological assessment of anxiety disorders: three-systems measurement and beyond. Psychological Assessment: A Journal of Consulting and Clinical Psychology, 3, 366–375. Whittal, M. L., & Goetsch, V. L. (1995). Physiological, subjective and behavioural responses to hyperventilation in clinical and infrequent panic. Behaviour Research and Therapy, 33, 415–422. Wilhelm, F. H., & Roth, W. T. (1999). Taking the laboratory to the skies: ambulatory assessment of self-report, autonomic, and respiratory responses in flying phobia. Psychophysiology, 35, 596–606. Wilhelm, F. H., & Roth, W. T. (2001). The somatic symptom paradox in DSM-IV anxiety disorders: suggestions for a clinical focus in psychophysiology. Biological Psychology, 57, 105–140. Wolpe, J. (1969). The practice of behavior therapy. New York: Pergamon Press.
Psychophysiological correlates of anxiety: A single-case study Laura E. Lewis *, Robert F. Drewett Department of Psychology, University of Durham, Durham, DH1 3LE, UK Received 26 April 2005; received in revised form 20 May 2005; accepted 31 August 2005
Abstract We examined the relationship between self-reported anxiety and physiological measures (blood pressure and heart rate) in a series of exposures to a feared situation of a single participant with panic disorder with agoraphobia. During each exposure, readings of heart rate, systolic blood pressure and diastolic blood pressure were taken every 20 s. Over 30 exposures, we found a near-linear relationship between anxiety and the three physiological measures. Implications of this result for usefulness of physiological measures in anxiety research and in the clinical treatment of anxiety disorders are discussed. # 2005 Elsevier Ltd. All rights reserved. Keywords: Anxiety; Psychophysiological; Assessment; Exposure; Heart rate; Blood pressure
1. Introduction Anxiety assessments in research and clinical work are predominantly derived from retrospective self-reports. Problems with exclusive use of self-report in the measurement of anxiety have led a number of authors to advocate the utility of physiological measures of anxiety (Nelson & Hayes, 1981; Orr & Roth, 2001; Rachman & Hodgson, 1974; Turpin, 1991; Wilhelm & Roth, 2001). Physiological measures are recommended because they are objective and, with advances in ambulatory techniques, they can be used continuously in real-world settings * Corresponding author at: Flat 28, Springfield House, 5 Tyssen Street, Dalston E8 2LY, UK. Tel.: +44 7862717266. E-mail address: [email protected] (L.E. Lewis). 0887-6185/$ – see front matter # 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.janxdis.2005.08.005
830
L.E. Lewis, R.F. Drewett / Anxiety Disorders 20 (2006) 829–835
(Nelson & Hayes, 1981). Lang’s (1978) three-systems approach to anxiety has provided both a structure and further rationale for inclusion of physiological measures in anxiety assessment. He argued that anxiety is manifest in three independent modes of response: cognitive, behavioral, and physiological. In this view, to emphasize one emotional response system to the exclusion of others neglects important aspects of anxiety. To justify use of physiological measures in research activity and clinical work, psychophysiological research seeks to establish a covariation between self-report and physiological measures of anxiety. Where a moderate covariation is known to exist, physiological assessment methods can be used with confidence to quantify anxiety symptoms objectively. In clinical work, the discrepancies between the two domains of response in the context of this covariation can facilitate the formulation of therapeutic intervention (Rachman & Hodgson, 1974). Most psychophysiological research investigating the link between anxiety and physiology has been conducted in the laboratory where it is easier to monitor and induce anxiety with a minimum of confounding variables. The often-cited concern about this laboratory research is its ecological validity and the generalizability of artificially inducing anxiety in an unnatural environment (Bystrisky & Shapiro, 1992; Whittal & Goetsch, 1995; Wilhelm & Roth, 2001). When anxiety is measured as it occurs naturally in a real-life setting, it is more representative of that experienced by individuals in their day to day lives (Bystritsky, Craeske, Maidenberg, & Shapiro, 1995; Wilhelm & Roth, 1999). Results from the handful of published studies of naturally occurring anxiety demonstrate that the majority of panic attacks are accompanied by elevations in physiological measures (Bystritsky et al., 1995; Freedman, Ianni, Ettedgui, & Puthezhath, 1985; Gaffney, Fenton, Lane, & Lake, 1988; Khawaja & Oei, 1999; Margraf, Taylor, Ehlers, Roth, & Agras, 1987; Shear et al., 1987; Taylor et al., 1986; Wilhelm & Roth, 1999). On the other hand, almost all the studies found that a certain proportion of the panic attacks that was monitored occurred without significant change in physiological measures. Gaffney and his colleagues (1988) found that 17 out of 31 naturally occurring panic attacks in panic patients were not associated with increased heart rates. In addition, none of these studies establishes a systematic covariation between anxiety states and physiological responses. One reason for this is that recordings were often made semicontinuously. Bystritsky and his colleagues (1995) monitored physiological responses of ten patients with panic disorder and 10 matched control subjects during regular daily activity. The ambulatory recorder was set to take recordings between two and five times an hour with the result that the patterns of change in heart rate and blood pressure from nonpanic to panic trials were inconsistent. Another problem with the methodology of previous naturalistic studies was that patients were not supervised when they recorded their anxiety feelings. Khawaja and Oei (1999) examined the psychophysiological correlates of anxiety semicontinuously in six panic disorder patients’ feared situations. The participants recorded when they started feeling anxious and how they were feeling every minute during the exposure. Heart rate
L.E. Lewis, R.F. Drewett / Anxiety Disorders 20 (2006) 829–835
831
data showed very little pattern of increase associated with self-reported anxiety. An important disadvantage of this study was that distress levels were not consistently reported by the participants during the panic attacks. Wilhelm and Roth’s (1999) study of anxiety in vivo demonstrates how ambulatory recording techniques can reliably be used to measure physiological responses in the natural environment. They carried out an assessment of selfreported anxiety and physiological measures during a 12-min flight in 14 people each meeting DSM-III-R criteria for simple flying phobia (American Psychiatric Association, 1987) and 15 controls matched for age and sex to the experimental group. Tested individually, the participants were linked to a multichannel monitoring device, which recorded changes in cardiovascular, electrodermal and respiratory activity. They were requested to rate their anxiety, tension, desire to leave and excitement on Subjective Units of Distress (SUD) scales from 0 to 10 at the end of preflight baseline, 3 min after take-off and at the end of postflight baseline. At these times, subjects were also requested to fill out questionnaires asking them ‘‘how they feel right now’’ and the 20-item STAI-State questionnaire (Spielberger, Gorsuch, & Luchene, 1970). Results showed that a 97% correct classification of subjects into anxious and nonanxious groups could be achieved using either the physiological or self-report measures. However, there were insufficient concomitant data to establish a correlation between self-reported anxiety and physiological measures of anxiety. In the present study, we aimed to examine the relationship between selfreported anxiety and physiological measures of anxiety in a single person with panic disorder with agoraphobia over multiple exposures to his feared situation. The opportunity to do so arose out of the participant’s desire to alleviate himself of a fear of chairlifts through habituation. He lived in a ski-resort and his work regularly took him on chairlifts. He agreed to accompany the first author on three different lifts, each triggering a different degree of anxiety, over a period of nine days on as many occasions as was practically feasible within his working schedule.
2. Method The participant of the study was a 51-year-old male who met DSM-IV criteria for panic disorder with agoraphobia (American Psychiatric Association, 1994). In addition to experiencing unexpected panic attacks in a variety of situations, he specifically feared travelling on a chairlift. Over 9 days, the participant took a total of 30 trips on chairlifts in three different locations, in which he reported varying degrees of anxiety (eight trips at location 0, the least feared, 15 at location 1, intermediate, and 7 at location 2, the most feared). A single trip lasted about 15 min. The first author accompanied the participant, and collected readings of blood pressure, heart rate, and anxiety every 20 s. Systolic blood pressure, diastolic blood pressure and heart rate were
832
L.E. Lewis, R.F. Drewett / Anxiety Disorders 20 (2006) 829–835
measured using an Omron MX3 blood pressure monitor strapped to the participant’s arm. Anxiety was assessed using the SUD scale (Wolpe, 1969), a self-report scale from 0 (not at all anxious) to 10 (the most anxious I could feel). The first author asked the participant to report his level of anxiety on a scale from 0 to 10 every 20 s concurrently with the cardiovascular recordings. The participant did not eat or exercise for an hour before each trip and, following a brief walk to the mountain lift, rested for 5 min before the start of the trip. In the chairlift the participant sat still and quietly with his arm flexed resting on a support at heart level.
3. Results Table 1 shows summary statistics for each variable at each location. Subjective units of distress (SUD) were considerably higher in location 1 than location 0, and higher still in location 2, with each of the physiological measures showing a corresponding pattern. The three physiological variables were highly correlated. The correlation (Pearson’s r) of diastolic and systolic blood pressure was .704, and their correlations with heart rate were .814 and .586, respectively. Fig. 1 shows the relationship between systolic blood pressure and subjective units of distress (SUD), pooled over the 30 trips. The correlation with SUD is .897 for systolic blood pressure. For diastolic blood pressure and for heart rate the corresponding correlations are .657 and .874, respectively. These relationships are monotonic and close to linear. The linear regression for systolic blood pressure is yˆ = 124 + 4.1 (SUD) where yˆ is the estimated value of systolic blood pressure in Table 1 Systolic and diastolic blood pressure, heart rate and subjective units of distress in the three different locations Location
Systolic blood pressure (mmHg)
Diastolic blood pressure (mmHg)
Heart rate (bmp)
Subjective units of distress
Mean N S.D.
129.58 250 6.07
91.37 250 4.46
77.64 250 2.73
1.50 250 1.29
Mean N S.D.
140.91 309 5.08
95.81 309 5.02
88.42 309 5.31
4.22 309 0.81
Mean N S.D.
148.21 283 4.65
100.09 283 5.43
98.39 283 5.33
5.87 283 0.90
0
1
2
N is the number of observations in each location.
L.E. Lewis, R.F. Drewett / Anxiety Disorders 20 (2006) 829–835
833
Fig. 1. Relationship between systolic blood pressure and subjective units of distress. The data are pooled over the three locations.
mm Hg and SUD is the integer value of subjective units of distress. For the other two variables the linear regressions are yˆ = 88.1 + 2.0 (SUD) for diastolic blood pressure and yˆ = 72 + 4.1 (SUD) for heart rate in beats per minute.
4. Discussion Pooled over 30 trips, the relationship between anxiety measured as SUD and systolic blood pressure was monotonic and linear (r = .897). Its relationships with diastolic blood pressure and heart rate were monotonic and close to linear, with r = 0.657 and 0.874, respectively. These strong correlations suggest that the participant’s anxiety comprised psychological and physiological changes that were concurrent and proportional. Present results show a systematic covariation between anxiety and physiological measures, demonstrating that physiological measures can reliably reflect anxiety states outside the laboratory. This adds weight to the argument that ambulatory assessment techniques have potential utility in research and clinical domains. To make plain this potential, Turpin (1991) identifies a number of ways in which anxiety research has benefited from the inclusion of psychophysiological assessment techniques. The study of the processes said to underlie the relationship between anxiety and behavior has relied upon the use of physiological measures (Bernstein, Borkovec, & Coles, 1986). In the field of psychiatric diagnosis and classification, phobic disorders have been differentiated by their psychophysiological correlates.
834
L.E. Lewis, R.F. Drewett / Anxiety Disorders 20 (2006) 829–835
The clinical utility of physiological measures is emphasized by a number of authors (Rachman & Hodgson, 1974; Turpin, 1991; Orr & Roth, 2001; Wilhelm & Roth, 2001). Physiological assessment methods can be used to quantify anxiety symptoms in the initial assessment of the problem and to monitor treatment success in terms of the reversal of physiological symptoms (Wilhelm & Roth, 2001). Where a moderate covariation is known to exist, discrepancies between the two domains of response can be used to facilitate the formulation of therapeutic intervention (Rachman & Hodgson, 1974). For instance, physiological measures can expose some degree of anxiety in individuals who are motivated to appear well-adjusted and misreport their true level of anxiety. The reverse pattern, in which an individual is highly anxious without showing much sign of physiological activation, may be an indication of a reduced threshold for symptom reporting. These discrepancies can throw light on a patient’s particular problem and can refine the choice of treatment for them. There are two principal limitations to this study. First, generalizability of the findings is limited given the use of a single participant. Second, the type of exposure employed in the study (sitting on a chair-lift) limits their clinical relevance. However, it should be possible to replicate the design of the study with other participants in situations which may be considered more clinically relevant using a broader range of physiological indices (e.g., electrodermal and respiratory responses). A series of such studies using the single-case approach across a variety of participants and in a range of clinically relevant settings may help to provide a better understanding of the relationship between self-reported anxiety and physiological measures.
Acknowledgement We thank the participant in this study for providing the original impetus for the research and for his brave cooperation throughout.
References American Psychiatric Association. (1987). Diagnostic and statistical manual of mental disorders (3rd ed., Rev.). Washington, DC: Author. American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington, DC: Author. Bernstein, D. A., Borkovec, T. D., & Coles, M. G. H. (1986). Assessment of anxiety. In: A. R. Ciminero, K. S. Calhoun, & H. E. Adams (Eds.), Handbook of behavioral assessment (pp. 353– 403). New York: Wiley. Bystrisky, A., & Shapiro, D. (1992). Continuous physiological changes and subjective reports in panic patients: a preliminary methodological report. Biological Psychiatry, 32, 766–777. Bystritsky, A., Craeske, M., Maidenberg, T. V., & Shapiro, D. (1995). Ambulatory monitoring of panic patients during regular activity: a preliminary report. Biological Psychiatry, 38, 684–689.
L.E. Lewis, R.F. Drewett / Anxiety Disorders 20 (2006) 829–835
835
Freedman, R. R., Ianni, E., Ettedgui, E., & Puthezhath, N. (1985). Ambulatory monitoring of panic disorder. Archives of General Psychiatry, 42, 244–248. Gaffney, F. A., Fenton, B. J., Lane, L. D., & Lake, C. (1988). Hemodynamic, ventilatory, and biochemical response of panic patients and normal controls with sodium lactate infusion and spontaneous panic attacks. Archives of General Psychiatry, 45, 53–60. Khawaja, N. G., & Oei, T. P. S. (1999). The psychobiological correlates of panic attacks during in vivo exposure. Behavioural and Cognitive Psychotherapy, 27, 353–367. Lang, P. J. (1978). Anxiety: toward a psychophysiological definition. In: H. S. Akiskal, & W. H. Webb (Eds.), Psychiatric diagnosis: exploration of biological Predictors (pp. 365–389). New York: Spectrum. Margraf, J., Taylor, C. B., Ehlers, A., Roth, W. T., & Agras, W. S. (1987). Panic attacks in the natural environment. Journal of Nervous and Mental Disease, 175, 558–565. Nelson, R. O., & Hayes, S. C. (1981). Theoretical explanations for reactivity in self-monitoring. Behavior Modification, 5, 3–14. Orr, S. P., & Roth, W. T. (2001). Psychophysiological assessment: clinical applications for PTSD. Journal of Affective Disorders, 61, 225–240. Rachman, S., & Hodgson, R. (1974). Desynchrony in measures of fear. Behaviour Research and Therapy, 12, 319–326. Shear, M. K., Kligfield, P., Harshfield, G., Devereux, R. B., Polan, J. J., Mann, J. J., et al. (1987). Cardiac rate and rhythm in panic patients. American Journal of Psychiatry, 144, 633–637. Spielberger, C. D., Gorsuch, R. L., & Luchene, R. E. (1970). State-trait anxiety inventory. Palo Alto: Consulting Psychology Press. Taylor, C. B., Sheikh, J., Agras, W. S., Roth, W. T., Margraf, J., Ehlers, A., et al. (1986). Ambulatory heart rate changes in patients with panic attacks. American Journal of Psychiatry, 143, 478–482. Turpin, G. (1991). The psychophysiological assessment of anxiety disorders: three-systems measurement and beyond. Psychological Assessment: A Journal of Consulting and Clinical Psychology, 3, 366–375. Whittal, M. L., & Goetsch, V. L. (1995). Physiological, subjective and behavioural responses to hyperventilation in clinical and infrequent panic. Behaviour Research and Therapy, 33, 415–422. Wilhelm, F. H., & Roth, W. T. (1999). Taking the laboratory to the skies: ambulatory assessment of self-report, autonomic, and respiratory responses in flying phobia. Psychophysiology, 35, 596–606. Wilhelm, F. H., & Roth, W. T. (2001). The somatic symptom paradox in DSM-IV anxiety disorders: suggestions for a clinical focus in psychophysiology. Biological Psychology, 57, 105–140. Wolpe, J. (1969). The practice of behavior therapy. New York: Pergamon Press.