Pain assessment in self-injurious patients with borderline personality disorder using signal detection theory

Psychiatry Research 70 Ž1997. 175]183

Pain assessment in self-injurious patients with borderline personality disorder using signal detection theory Ingrid Kempermana,U , Mark J. Russ b , W. Crawford Clark c , Tatsuyuki Kakumaa , Elizabeth Zanine a , Katherine Harrison a a

The New York Hospital, Cornell Medical Center, 21 Bloomingdale Road, White Plains, NY 10605, USA Hillside Hospital, Long Island Jewish Medical Center, 75]59 263rd Street, Glen Oaks, NY 11004, USA c College of Physicians and Surgeons, Columbia Uni®ersity and The New York State Psychiatric Institute, 722 West 168th Street, New York, NY 10032, USA b

Received 24 June 1996; revised 23 January 1997; accepted 24 March 1997

Abstract Signal detection theory measures of thermal responsivity were examined to determine whether differences in reported pain experienced during self-injurious behavior in female patients with borderline personality disorder ŽBPD. are explained by neurosensory factors andror attitudinal factors Žresponse bias.. Female patients with BPD who do not experience pain during self-injury ŽBPD-NP group. were found to discriminate more poorly between noxious thermal stimuli of similar intensity, low P Ž A., than female patients with BPD who experience pain during self-injury ŽBPD-P group., female patients with BPD who do not have a history of self-injury ŽBPD-C group., and age-matched normal women. The BPD-NP group also had a higher response criterion, B Žmore stoical. than the BPD-C group. These findings suggest that ‘analgesia’ during self-injury in patients with BPD is related to both neurosensory and attitudinalrpsychological abnormalities. Q 1997 Elsevier Science Ireland Ltd. Keywords: Pain perception; Personality disorder; Self-mutilation; Parasuicide; Sensory decision theory; Dissociation; Opiate

U

Corresponding author. Tel.: q1 914 9975745 or q1 212 7463943.

0165-1781r97r$17.00 Q 1997 Elsevier Science Ireland Ltd. All rights reserved. PII S0165-1781Ž97.00034-6

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1. Introduction Most self-injurious patients with borderline personality disorder ŽBPD. experience a relief in dysphoria associated with self-injury. About one half of these patients report that they typically do not experience pain during self-injurious behavior ŽSIB.. This ‘analgesic’ group of self-injurious patients differs from similar patients who report experiencing pain during SIB in that they report feeling less pain and an enhancement in mood during a laboratory pain procedure ŽRuss et al., 1992. and suffer from more severe psychopathology ŽRuss et al., 1993.. One interesting possibility is that the mechanisms of pain perception and affect regulation are biologically related, e.g. by involving a common neurotransmitter system such as the endogenous opiate system ŽCoid et al., 1983; Richardson and Zaleski, 1983. or the serotonin system ŽSimeon et al., 1992.. Investigating the neurosensory basis for the differences in pain perception among these self-injurious patients may help elucidate the biology of SIB. Pain is a subjective experience with sensory, emotional, cognitive, and sociocultural components. We cannot assume that differences in pain report during SIB are due to differences in neurosensory function alone. In order to determine the basis for the differences in pain report among self-injurious patients with BPD, we need to distinguish between the neurosensory and other factors, largely attitudinal and emotional, that contribute to pain report. Many of the traditional methods for measuring sensory function, such as threshold determination, do not make this distinction. For example, if a subject has a ‘high pain threshold,’ there is no way of knowing whether she has a sensory deficit or is merely ‘stoical’, i.e. sets a high criterion for reporting pain. We have employed Signal Detection Theory ŽSDT. because there is considerable evidence that it can distinguish neurosensory and attitudinal factors. SDT yields two measures of perceptual performance ŽClark, 1994; Clark, in press.. In the non-parametric model ŽMcNichol, 1972., the discriminability measure, P Ž A., reflects the accuracy with which a subject makes a discrimination between two stimuli of slightly different intensity.

The response criterion, B, quantifies the subject’s response bias, that is, the general tendency to report one of the events as occurring more frequently than the other. In the single-interval SDT rating procedure, subjects are asked to rate the magnitude of the pain experience Žusing a categorical scale. for stimuli of different intensities presented repeatedly in a random manner. Discriminability is related to the difference between the ‘hit’ rate Žrate of correctly designating the higher intensity stimulus as more intense or painful. and false alarm rate Žrate of incorrectly designating the lower intensity stimulus as more painful.. A high hit rate coupled with a low false alarm rate yields a high value of P Ž A., indicating good discriminability. As these two rates approach each other, discriminability worsens until, when they are equal, the observer’s performance is at chance level P Ž A. s 0.5. The response criterion, B, is related to the sum of the hit and false alarm rates. For example, if a subject has a low response criterion Žreadily reports pain., she will have an increased tendency to both correctly designate higher stimuli as painful Žhigh hit rate. as well as incorrectly designate the lower stimuli as similarly painful Žhigh false alarm rate.. Several studies have investigated physiological and psychological variables that influence these measures. Discriminability, P Ž A., has been found to decrease when an analgesic is administered ŽChapman et al., 1973; Yang et al., 1979.. Therefore P Ž A. has been assumed to indirectly measure aspects of pain sensitivity related to neurosensory functioning. The response criterion, B, has been shown to be affected by manipulation of attitudinal and psychological factors; P Ž A. is not. Clark Ž1969. demonstrated that the administration of a placebo described as a strong analgesic increased the response criterion Žfewer pain reports. without altering the discriminability. Clark and Goodman Ž1974. found that the response criterion was lowered Žmore pain reports. when subjects were told that previous thermal stimulation would render the skin more sensitive; while the opposite suggestion to a different group raised the criterion. Other studies have demonstrated that response criterion is related to ethnocultural

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background, age, and gender ŽClark and Yang, 1983.. The primary aim of this study was to explore the basis for differences in pain report in subgroups of self-injurious patients with BPD. The responses of self-injurious patients with BPD to noxious and non-noxious thermal stimuli of different intensities were examined using Signal Detection Theory. For purposes of comparison, patients with BPD with no history of SIB and age-matched normal women were also studied. By measuring discriminability, P Ž A., and response criterion, B, in a laboratory SDT paradigm, we hoped to determine whether group differences in pain report are related to neurosensory factors, attitudinalremotional factors, or both. Measures of dissociation, anxiety, and depression were also obtained, as these factors may influence pain report ŽClark and Yang, 1983.. 2. Methods Data were collected from 43 female subjects ages 18]52. Thirty-four of these were in-patients who met DSM III-R ŽAmerican Psychiatric Association, 1987. criteria for BPD as determined by the Structured Clinical Interview for DSM III-R Personality Disorders ŽSCID II, Spitzer et al., 1987.. Patient charts were reviewed to obtain information about concurrent axis-I diagnoses and medication treatment. SCID-P ŽSpitzer et al., 1988. and SCID II were used to rule out axis-I and axis-II disorders in nine normal control subjects. Most subjects completed the following self-report measures: Dissociative Experiences Scale ŽDES, Bernstein and Putnam, 1986.; Sheehan Patient Rated Anxiety Scale ŽSPRAS, Sheehan et al., 1988.; and the Beck Depression Inventory ŽBDI, Steer et al., 1986.. The number of subjects who completed each self-report measure is given in Table 3. Subjects were determined to be selfinjurious if they had a history of five or more episodes of SIB, defined as self-inflicted injury that causes direct tissue damage and is not lethal in severity or intent. Subjects without a history of SIB were studied as the comparison group ŽBPDC group.. Self-injurious subjects were interviewed

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to determine the age of onset, type and number of episodes of SIB. Self-injurious subjects with BPD were assigned to one of two groups based on their responses on a questionnaire designed to quantify the intensity of pain report Žranging from ‘no sensation’ to ‘severe pain’. during episodes of SIB, as well as the variability of pain report across episodes. A subject was assigned to the group that reports not typically feeling pain during self-injury ŽBPD-NP group. if she reported ‘no sensation’ or ‘touchrpressure’ during 75% of episodes, and no more than ‘slight discomfort’ Žthe next highest intensity category. during the remaining 25%. Self-injurious subjects not meeting these criteria were assigned to the BPD-P group. Signal Detection Theory testing using heat stimuli was similar to the method of Clark Ž1974.. The Hardy-Wolff Goodell dolorimeter was used to administer the heat stimuli. This device consists of a 100-W light bulb housed in a hand-held gun-like projector that delivers measured quantities of radiant heat for a specified duration. The subjects were free to remove the apparatus from their skin at any time. The heat stimuli, each lasting 3 s, were delivered to 2-cm diameter areas of skin which had been painted with India ink. Six heat stimuli ranging from 50 mcalrsrcm 2 to 370 mcalrsrcm 2 were administered in ascending order Žmethod of limits. to each subject in order to give them a sense of the range of stimuli. All subjects rated at least one stimulus intensity as painful. For the SDT procedure, 40 stimuli, randomized with respect to temperature, were applied in order to 10 sites on each forearm. The four stimulus intensities used were non-noxious Ž50 and 100 mcalrsrcm 2 , 33.78C and 36.28C, respectively. and noxious Ž320 and 370 mcalrsrcm 2 , 46.08C and 49.58C, respectively.. The sequence of stimuli permitted the skin to return to base temperature and ensured that each spot received no more than two noxious stimuli. Subjects rated the intensity of each stimulus using a categorical scale; the withdrawals were also scored. The scale’s response categories along with the corresponding B values are shown in Table 1. It was found that two of the normal control subjects exhibited ‘zero’ or ‘chance’ discriminability. We believe that they did not adequately per-

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Table 1 Relationship between B, response criterion, values and rating categories Ba Rating a b

8 Nothing

7 Maybe something

6 Warm

5 Hot but not painful

4 Faint pain

3 Moderate pain

2 Severe pain

1 Withdrawal b

The values of the criterion, B, were not viewed on the scale by the subject. Withdrawal was not a category on the scale viewed by the subject.

form the task as they immediately withdrew from every noxious stimulus. It is unlikely that these two subjects had time to experience the stimuli in order to make a discrimination, rather than that they were pain insensitive, as their zero Žor chance, P Ž A. s 0.50. discrimination would suggest. It appears that these two subjects had a strong affective reaction to the procedure such that any noxious stimulus was dealt with in the same way, i.e. withdrawal. This is highlighted by one of the subjects who withdrew every time a noxious stimulus was given, while only rating these stimuli as ‘moderately painful’. Therefore these two normal controls were excluded from statistical analyses. No other subjects in the study responded in this manner. This study was approved by our Institutional Review Board, and all subjects gave written informed consent prior to participation. 2.1. Data analysis The stimulus-response data were analyzed separately for the lower and upper pairs of stimulus intensities by non-parametric SDT procedures ŽMcNichol, 1972. to obtain the values of P Ž A. and B for each subject. P Ž A. was computed by the trapezoidal rule as the area below the receiver operating characteristics ŽROC. curve generated by cumulating probabilities of hits and false alarms at each response category. B was determined as the rating scale criterion at which half the responses Žto both stimulus intensities in each pair. are to higher response categories and half are to lower. Group means for P Ž A. and B, as well as the DES, SPRAS, and BDI scales, were also compared using one-way analysis of variance

ŽANOVA.. Analysis of covariance ŽANCOVA. was used to test specific hypotheses about the contributions of the psychological measures to group differences in response criterion. 3. Results The mean age Ž"S.D.. of the normal control and BPD groups ŽBPD-NP, BPD-P, and BPD-C. was 26.9" 6.5 years, 28.3" 9.7 years, 31.5" 8.2 years, and 32.1" 8.2 years, respectively Ž F3,37 s 0.90, Ps 0.45.. The mean admission global assessment of functioning ŽGAF. score, type of SIB, age of onset of SIB, number of lifetime episodes of SIB, axis-I diagnoses during hospitalization and medication administered for the BPD groups are shown in Table 2. The BPD groups did not differ with respect to their GAF score, age of onset of SIB, or the number of lifetime episodes of SIB. The type of SIB most commonly engaged in for both the BPD-P and BPD-NP groups was superficial cutting. Chi-square tests revealed no significant group differences in category of axis-I diagnosis Žminimum Ps 0.32. or category of medication used Žminimum Ps 0.31.. Significant differences among groups were found for pain discriminability Ž P Ž A., F3,37 s 7.09, Ps 0.0007., and response criterion Ž B, F3,37 s 3.49, Ps 0.025. for the noxious stimulus pair ŽTable 3.. Post-hoc ŽBonferroni. comparisons revealed that P Ž A. values were significantly lower for the BPD-NP group compared to all other groups Ž P values ranged from 0.002 to 0.0004., and B values were significantlyhigher for the BPD-NP group compared to the BPD-C group Ž Ps 0.0055.. Although the mean value for B for the BPD-NP group was also higher than those for the BPD-P and normal groups, these differences

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Table 2 BDP group comparsions for axis-I diagnosis, GAF score, medication use, and self-injurious behavior ŽSIB.

AXIS-I diagnosis a Affective disorder Substance abuse Eating disorder Dissociative disorder Admission GAF score b Medication c Antidepressants Antipsychotics Mood stabilizers Benzodiazepines Type of SIB Age of onset of SIB d Number of episodes of SIB e

BPD-NP Group Ž n s 9.

BPD-P Group Ž n s 17.

BPD-C Group Ž n s 8.

7 0 1 0 37.7" 9.1

13 1 0 2 36.7" 11.0

8 1 1 0 37.4" 7.4

4 3 2 3 Cutting 19.3" 10.8 317 " 742.7

9 5 9 3 Cutting 20.1" 10.1 57.3" 75.5

6 4 3 1 } } }

a

One admission diagnosis per subject, except one subject in the BPD-C group with three diagnoses. Non-significant: F2, 31 s 0.03, Ps 0.97. c Numbers refer to number of subjects that received particular class of medication. Most subjects received more than one type of medication. d Non-significant: F1,18 s 0.04, Ps 0.84; nŽBPD-NP. s 7, nŽBPD-P. s 13. e Non-significant: F1,17 s 1.5, Ps 0.24; nŽBPD-NP. s 7, nŽBPD-P. s 12. b

did not reach statistical significance. Response criterion values of the noxious stimulus pair for the four groups corresponded to the descriptor categories as follows: BPD-NP Žbetween ‘hot but not painful’ and ‘faint pain’.; BPD-P Žbetween ‘moderate pain’ and ‘severe pain’.; BPD-C Žbetween ‘ moderate pain’ and ‘severe pain’.; Normal Žbetween ‘faint pain’ and ‘moderate pain’.. There were no other significant differences among groups. Moreover, no differences among groups were found for the non-noxious stimuli. Group differences were also found for measures of dissociation ŽDES, F3,34 s 7.44, Ps 0.0006., anxiety ŽSPRAS, F3,32 s 11.75, P s 0.0001. and depression ŽBDI, F3,37 s 12.93, Ps 0.0001, Table 3.. Inspection of the group means for all these measures reveals that the highest scores were those of the BPD-NP group, followed by the BPD-P group, and then the BPD-C group. The normal control group had the lowest mean score on all measures, as would be expected. The post-hoc comparisons describing the statistically significant group differences for the DES, BDI and SPRAS scales are summarized in Table 3.

Auxiliary analyses were performed to better understand the relationship between the psychological measures and P Ž A. and B. A Pearson correlation of all measures revealed only a single significant correlation, that between B and DES score Ž r s 0.36, Ps 0.027.. Analyses of covariance ŽANCOVAs. were performed using those variables where significant group differences were found, i.e. DES, SPRAS, and BDI, to determine whether they accounted for the observed group differences in P Ž A. and B. None of these variables were found to be significant covariates of P Ž A. or B.

4. Discussion

The patients with BPD who reported an absence of pain sensation during SIB ŽBPD-NP group. were less able to distinguish between painful stimuli of similar intensity } lower discriminability, P Ž A. } compared to the patients with BPD who reported pain during SIB ŽBPD-P

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Table 3 Group comparsions for discriminability, response criterion, and psychological measures BPD-NP group Ž n s 9. Mean " S.D. P Ž A.-noxious a Ž320]370 mcalrsrcm 2 . P Ž A.-warmb Ž50]100 mcalrsrcm 2 . B-noxious c Ž320]370 mcalrsrcm 2 . B-warmd Ž50]100 mcalrsrcm 2 . Dissociative exp scale e Sheehan anxiety scale f Beck depression inventory g

BPD-P group Ž n s 17.

BPD-C group Ž n s 8.

Normal group Ž n s 7.

0.63" 0.1

0.79" 0.1

0.79" 0.08

0.82" 0.06

0.65" 0.09

0.73" 0.10

0.67" 0.11

0.71" 0.12

4.6 " 1.7

2.9 " 1.6

2.3 " 1.6

3.7 " 0.49

9.1 41.4 68.8 32.9

" 0.6 " 19.1 " 28.9 " 13.8

8.6 26.7 58.7 29.2

" 0.7 " 12.2 " 20.2 " 10.7

8.6 22.8 37.5 22.6

" 0.6 " 14.3 " 20.6 " 10.5

8.4 5.4 3.2 2.7

" 0.68 " 3.8 " 4.3 " 1.6

a

F3,37 s 7.09, Ps 0.0007. BPD-NP- BPD-P, BPD-C, Normal. Non-significant: F3,37 s 1.25, Ps 0.30. c F3,37 s 3.49, P s 0.025. BPD-NP) BPD-C. d Non-significant: F3,37 s 1.26, Ps 0.21. e F3,34 s 7.44, Ps 0.0006.Normal- BPD-NP and BPD-P; nŽBPD-NP. s 9, nŽBPD-P. s 16, nŽBPD-C. s 6, n ŽNormal. s 7. f F3,32 s 11.75, Ps 0.0001. Normal- BPD-NP, BPD-P, BPD-C; BPD-NP) BPD-C; nŽBPD-NP. s 9, nŽBPD-P. s 15, nŽBPD-C. s 5, nŽnormal. s 7. g F3,37 s 12.93, Ps 0.0001. Normal- BPD-NP, BPD-P, BPD-C; nŽBPD-NP. s 9, nŽBPD-P. s 17, nŽBPD-C. s 8, nŽnormal. s 7. b

group., the patients with BPD but without a history of SIB ŽBPD-C group., and normal controls. Moreover, the BPD-NP group was also more conservative Žor stoical. in designating these perceived stimuli as painful Žhigher response criterion, B . compared to similar patients without a history of self-injury ŽBPD-C group.. Response criterion has generally been found to be unrelated to discriminatory aspects of pain appreciation ŽClark and Yang, 1983.. Response criterion, B, and P Ž A. were in fact not correlated in this study ŽPearson r s y0.056, Ps 0.73.. It is important to note that P Ž A. and B did not differ among groups for the non-noxious Žwarm. pair of stimuli, demonstrating that our findings are specific for pain, and do not merely reflect non-specific differences Žsuch as attention or motivation. in the processing of sensory input. Previous research has shown that P Ž A. is decreased following the administration of a variety of analgesic agents ŽChapman et al., 1973; Yang et al., 1979.. Therefore, discriminability may be a physiologically based, neurosensory aspect of pain

perception. In this study, the decreased discriminability observed in the BPD-NP group may, in part, reflect pain insensitivity on the basis of abnormal neurosensory processing. In addition, we found that the response criterion, B, of the BPD-NP group was highest compared to those of the other groups, although significantly different only in comparison with the BPD-C group. Response criterion, but not disc r im in a b ilit y , g e n e r a lly r e fl e c t s t h e emotionalrattitudinal aspects of pain. In our study, DES scores were significantly correlated with response criterion, possibly suggesting that response criterion was related to a tendency to deny pain on a cognitive level, or ‘block out’ the affective component of the experience. This is consistent with the clinical literature in which analgesia during SIB in borderline patients has often been attributed to concomitant dissociative symptoms such as derealization and depersonalization Žvan der Kolk and Saporta, 1991.. There are a number of possible limitations of this study. The sample size was small, most of the

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subjects with BPD were receiving medication, and most had a comorbid axis-I diagnosis of major depression. The latter two Žmedication and comorbid diagnosis. are potential confounding factors. While some medications have demonstrable analgesic properties in clinical pain, most studies have failed to find an analgesic effect in laboratory pain ŽClark and Mehl, 1976; Chapman and Butler, 1978; Ward, 1986; Atkinson, 1989.. Moreover, there were no significant differences among the groups with BPD in the types of medications used. If medications were a significant factor in decreasing pain sensitivity, one would have expected the normal control group Žfree of medication. to be more pain sensitive than the BPD subjects Žmost of whom were receiving medication.. In fact, no significant differences in P Ž A. or B between the normal control group and the BPD-P and BPD-C groups were observed despite the differences in medication use. In the absence of studying patients who are free of medication, however, this issue cannot be definitively resolved. The fact that most of the patients with BPD were also diagnosed with an affective disorder Žmostly major depression. may present another potential confound in this study. A number of studies indicate that patients with affective disorders have altered pain thresholds compared to normal subjects ŽHall and Stride, 1954; Merskey, 1965; von Knorring, 1975. as well as altered discriminability and response criterion ŽDavis et al., 1979; Dworkin et al., 1995.. In our study we found that in the patients with BPD there were no group differences in the number of subjects with affective disorders Žmostly major depression. or in the severity of depression Žas measured by the BDI. despite group differences in P Ž A. and B. Moreover, BDI was not a correlate or covariate of P Ž A. or B. These findings suggest that our observed group differences in P Ž A. and B were not related to depression. The neurobiological bases for these differences in pain discriminability and response bias are unknown. Recent work has suggested the interesting possibility that discriminability and response bias have separate neuroanatomical substrates ŽCoghill et al., 1994.. Discrimination of

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pain stimuli may take place in the primary somatosensory cortex and the more lateral thalamic nuclei, together termed the ‘lateral pain system’ ŽMelzack, 1986; Greenspan and Winfield, 1992.. The ‘medial pain system’ composed of the medial thalamic nuclei and their diffuse cortical projection sites including frontal, cingulate, and insular cortices Žwhich in turn have connections with the limbic system. may be involved in the affective and motivational aspects of pain processing ŽFriedman and Murray, 1986; Berthier et al., 1988.. There is evidence that the medial pain system contains higher concentrations of opioid peptides and receptors relative to the lateral system ŽJones et al., 1991.. Involvement of the endogenous opioid system has been suggested to explain pain insensitivity in self-injurious patients ŽDavies et al., 1982; Richardson and Zaleski, 1983; Coid et al., 1983; van der Kolk et al., 1985.. Opioid receptor blockade has been found to decrease self-mutilation in mentally retarded individuals ŽHerman et al., 1987; Sandman et al., 1987.. Recently, naltrexone has been found to decrease self-injurious behavior in an open-label trial of seven female patients with normal intelligence and a history of SIB accompanied by analgesia and dysphoria reduction ŽRoth et al., 1996.. If our ‘analgesic’ patients with BPD are generally insensitive to painful stimuli, the pathogenesis of such a condition is unclear. Developmental factors such as early trauma may diminish pain sensitivity in adulthood ŽMelzack and Scott, 1957; Rosenthal and Rosenthal, 1984.. In this regard, a history of childhood sexual abuse has often been described in patients with BPD who engage in SIB Žvan der Kolk and Saporta, 1991., and may even be more common in the analgesic subgroup ŽRuss et al., 1993.. The analgesic subgroup could represent a distinct subset of self-injurious patients with BPD who experienced particularly severe or early trauma. The results of this study lend support to the hypothesis that the relative analgesia during selfinjury reported by a subgroup of patients with BPD may reflect neurophysiological abnormalities as well as psychological factors. The characterization of pain insensitivity in this subgroup

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