Fear activation and habituation patterns as early process predictors of response to prolonged exposure treatment in PTSD

Journal of Traumatic Stress, Vol. IS . No. 5, October 2002. pp. 359-367 (0 2002)

Fear Activation and Habituation Patterns as Early Process Predictors of Response to Prolonged Exposure Treatment in PTSD

Agnes van Minnenl ,2 and Muriel H a g e n a a r s l

Improved (n = 21) and nonimproved (n = 13) PTSD patients (a mixed trauma population) were compared for fear activation and habituation patterns during and between the 1 st and 2nd prolonged exposure sessions. Drop-outs (n = 1 1) were also evaluated. Nonimproved patients had significantly higher ratings of anxiety at the start of the first exposure session. Improved patients showed more within-session habituation during the self-exposures at home and more between-session habituation. Even after controlling for initial PTSD and depression symptom severity, habituation between the first and second exposure sessions was significantly related to treatment outcome. Patients who dropped out of the treatment were found not to differ from completers on fear activation and within-session habituation during the first exposure session.

KEY WORDS: PTSD; exposure treatment; fear activation; habituation; treatment process.

Although several studies have shown that prolonged exposure is effective in the treatment of patients with posttraumatic stress disorder (PTSD; Boudewyns & Hyer, 1990; Cooper & Clum, 1989; Foa et al., 1999; Keane, Fairbank, Caddell, & Zimering, 1989; Marks, Lovell, Noshirvani, Livanou, & Thrasher, 1998; Tarrier et al., 1999), a considerable number of patients (some 25- 45%) still have PTSD at the end of treatment, indicating that exposure therapy may produce improvement, but not always recovery. The detection of outcome predictors in the early stages of treatment might improve results, for instance by adjusting treatment protocols for those patients unlikely to improve.

Several studies have investigated the predictive value of pretreatment variables such as symptom severity, co- morbidity, trauma characteristics (including time since

'Department of Clinical Psychology and Personality, University of Nijmegen. The Netherlands. *To whom correspondence should be addressed at Department of Clinical Psychology, Universityof Nijmegen, POBox 9104.6500HENijmegen. The Netherlands; e-mail: [email protected].

trauma, nature of trauma), personality pathology, demo- graphics and feelings of anger, shame, and guilt. With the exception of pretreatment PTSD symptom seventy, however, these variables have been found to be insignifi- cant or unstable predictors of treatment success (e.g., Van Minnen, Amzt, & Keijsers, 2002). Therefore, it may be worthwhile to look more closely at the relationships between treatment outcome and the relevant processes during and between the exposure sessions than to focus on pretreatment characteristics.

Emotional processing has been found to be a cru- cial process in the exposure treatment of anxiety disorders in general. Foa and Kozak (1986) postulated the emotional processing theory, taking Lang's model of bioinfor- matical processing (Lang. 1979) and Rachman's work on the concept of emotional processing (Rachman. 1980) as their basis. According to the Foa and Kozak theory, emotional processing during exposure to feared stimuli has to meet two conditions to be effective. First, the fear structure must be adequately activated during the exposure. Several studies have shown that fear activation during exposure therapy, defined as both physiological

359 0894-9&71oUlOO0-0359/1 0 2002 Intcrnamal Socwy for Tnumalic Svcss Studies

Minnen and Hagenaars

indications of fear, such as increased heart rate, and as subjective ratings of anxiety, is positively related to treatment outcome in several anxiety disorders (e.g., Borkovec & Sides, 1979; Foa & Kozak, 1986; Kozak, Foa, & Steketee, 1988; Lang, Melamed, & Hart, 1970; Watson & Marks, 1971). As a second condition, Foa and Kozak theorized that, during the exposure, new information incompatible with the anxiety-evoking information must be incorpo- rated into the memory structure. As indicators of this process, patients show a decrease in fear responses during the exposure session (within-session habituation) and across sessions (between-session habituation). Again, evidence for this was found in several studies. Anxiety disorder patients showed habituation, measured both physiologi- cally and subjectively, during exposure to feared stimuli (e.g., Borkovec, 1972; Foa & Chambless, 1978; Grayson, Foa, & Steketee, 1982; Nune & Marks, 1975; Stem & Marks, 1973; Watson, Gaind, & Marks, 1972).

To date, there have been very few studies that have examined emotional processing theory in connection with exposure therapy for PTSD patients. Those that have ap- pear to support Foa and Kozak’s theory. In one study, it was found that in female assault victims with PTSD, fear activation, measured as facial expressions of fear during the first exposure session, was positively related to treatment improvement (Foa, Riggs, Massie, & Yarczower, 1995). In another study of 20 Vietnam veterans who underwent imaginal flooding therapy, a greater increase in heart rate during the first flooding session was positively related to treatment outcome (Pitman et al., 1996). Jaycox, Foa, and Morral(1998) studied fear activation and habituation patterns in relation to treatment outcome in PTSD patients who underwent prolonged imaginal exposure. Based on average subjective ratings of anxiety during and across six exposure sessions, patients who experienced high initial fear activation and gradual habituation across sessions had better end-state functioning than patients showing low fear activation and no habituation, indicating that fear activation and between-session habituation are important processes during exposure treatment in PTSD. However, in contrast with the theory, within-session habituation was not related to end-state functioning.

Taken together, several studies point to the importance of the process of fear activation and habituation in relation to treatment outcome. This study evaluated the predictive value of fear activation and habituation in an early treatment phase. A comparison was made between improved and nonimproved PTSD patients, with respect to patterns of subjective anxiety levels during and between the first two prolonged exposure sessions. These patterns were also evaluated for patients who dropped out of treatment. Furthermore, fear activation and habituation

patterns during repeated self-exposures at home were evaluated in relation to treatment outcome, as was homework compliance.

Based on the emotional processing theory, it was hy- pothesized that improved patients, in comparison with nonimproved patients and dropouts, would show ( I ) a higher increase in subjective ratings of anxiety during the first exposure session, as an indication of fear activation, (2) a greater decline in subjective ratings of anxiety within each exposure session and within the self-exposure sessions at home (within-session habituation), and (3) a greater decline in subjective ratings of anxiety between the sessions (between-habituation).

Method

Participants

Participants were clinical referrals to a university outpatient clinic and an outpatient clinic specializing in the treatment of anxiety disorders. All participants met DSM-Ill-R (American Psychiatric Association [APA]. 1987) or DSM-IV(APA, 1994) criteria for chronic PTSD, established through clinical interviews in which the DSM criteria for PTSD were explicitly checked by two independent assessors (kappa = .96), using the Munich Diagnostic Checklists for mood and anxiety disorders (Hiller, Zaudig, & Mombour. 1990). Given our research question, only participants whose SUDS ratings from the first exposure session were available ( N = 45) w&e included.

Trauma history was obtained using a standard protocol. Participants had experienced various traumatic events preceding the PTSD: having witnessed or having been in- volved in accidents (n = 12), finding a dead person after a suicide or homicide (n = 1 I). sexual violence (n = 9), (domestic) violence (n = 8), and work-related traumas (police and firemen; n = 5). Six participants had experienced their trauma in childhood, 39 participants in adult- hood. Seventeen participants had had multiple traumatic events in the past; 28 participants had experienced a single traumatic event. At the start of the treatment, mean time since trauma was 4 years and 9 months (SD = 57 months, range 3-276 months).

Thirty-four participants completed the exposure treatment (completers). The group of completers consisted of 17 men and 17 women. Mean age was 35.1 years (SD = 9.2). Eleven participants (24.4%) dropped out of treatment (dropouts). Seven of these dropped out at a very early stage-in fact before the second treatment session. The dropout group consisted of 6 men and 5 women. Their mean age was 34.8 years (SD = 1 I .4).

Fear Activation and Habituation Patterns 361

Procedure

The participants included in the study all met the DSM-criteria for PTSD as the primary diagnosis and had been suffering from the condition for 3 months or more.

Assessment 1 took place before the start of the exposure sessions (pretreatment), and Assessment 2, two weeks after the last (9th) exposure session (posttreatment). The assessments were conducted by independent assessors.

Treatment

Treatment consisted of prolonged imaginal exposure sessions, based on the treatment programme described by Foa, Rothbaum, Riggs. and Murdock (1991). In a pretreatment session, participants were given information about FTSD symptoms, their development and maintenance. In addition, the treatment procedure was described and its rationale carefully explained. After this pretreatment session, participants received nine weekly prolonged imaginal exposure sessions. Imaginal exposure was sustained for 60 min per session. Each exposure session was audiotaped and participants were instructed to listen to the tape five times a week at home.

Therapists

Participants were treated using a detailed treatment protocol. Therapists were psychologists who had been trained in prolonged exposure therapy in the treatment of PTSD. Treatments were on a weekly basis and were super- vised by experienced clinical psychologists and cognitive- behavioural therapists.

Instruments

Treatment Outcome

The main outcome measure was the PTSD Symp- tom Scale Self-Report (PSS-SR; Foa, Riggs, Dancu, & Rothbaum, 1993). The items (range 0-3) provide both diagnostic and severity information about each of the 17 DSM-IV criteria for PTSD. Total scores range from 0 to 51. Higher scores indicate more PTSD symptoms. The scale contains three subscales: reexperience, arousal, and avoidance. The PSS-SR showed good reliability and validity in a sample of female assault victims (Foa et al., 1993). The Dutch translation of the PSS-SR also shows high internal consistency (Cronbach’s alpha = .96).

The Dutch version of the State Anxiety Inventory (STAl-State; Spielberger, Gorsuch, & Lushene, 1970;

Van der Ploeg. Defares, & Spielberger, 1980) was used as a general measure of anxiety. This inventory includes 20 items about the level of anxiety at that particular mo- ment, each ranging from 0 to 4. Higher scores indicate more anxiety. The internal consistency (Cronbach’s alpha) of the Dutch State version is .93. The depression subscale of the Symptom Checklist-90-Revised (SCL- 90-R; Dutch adaptation: Amndell & Ettema, 1986) was also used. This checklist consists of 16 items, each ranging from 1 to 5. Again, higher scores indicate more depression. Cronbach’s alpha for the Dutch SCL-Total Scale was .97, and for the Depression Subscale .93.

Subjective Levels of Anxiety

During the exposure sessions, anxiety levels were monitored regularly using the Subjective Units of Dis- tress Scale (SUDS), a 0-10 scale, with 0 indicating no feelings of anxiety at all and 10 the maximum level of anxiety. Seven scores on the SUDs were obtained in each session: at the beginning of the 60-min exposure (SUD start), every 10 min during the exposure and at the end of the exposure (SUD end). SUDs scores from the first two exposure sessions (S I and S2) were analysed in this study.

Each exposure session was audiotaped. and participants were instructed to listen to the tape at home five times a week. They were instructed to write down the SUDs before they began and after they had finished listening to the tape. Furthermore, they were to note the highest peak in anxiety they had felt whilst listening to the tape. Home- rated SUDs between the first and second exposure sessions were analysed in the present study.

Fear Activation

Averaging the seven SUDs ratings from each session provided a mean SUDs rating per patient, per session. In addition, for each session, the highest SUDs rating was taken as the peak SUD and the first SUD rating was subtracted from this in order to determine the degree of increase in anxiety during exposure.

As a measure of fear activation at home, the mean peak SUD score was computed on the basis of all available SUD ratings at home between S 1 and S2. In addition, mean start SUD ratings were subtracted from mean peak SUD ratings.

Within-Sesswn Habituation

Within-session habituation for the treatment sessions was calculated by subtracting the end SUD rating from the

362 Minnen and Hagenaars

peak SUD rating in each session (see also Jaycox et al., 1998; Kozak et al.. 1988). Within-session habituation at home was calculated by subtracting the end SUD rating from the peak SUD rating for each day.

Between-Session Habituation

Between-session habituation was calculated by subtracting the mean or peak SUDs of S2 from the mean or peak SUDs of S1. In addition, mean peak SUD ratings at home were subtracted from the peak SUD in S1.

Homework Compliance

The exposure during S 1 was audiotaped. Participants were instructed to listen to the tape at home five times between S 1 and S2. The number of times they actually listened to the tape at home (range 0-5) was used to establish homework compliance.

lkeatment Improvement

Since successful therapy should include improve- ments on several dimensions, rather than on a decline in PTSD-symptoms alone, we used, in accordance with the Jaycox et al. (1998) study, an end-state functioning criterion based on measures of PTSD symptoms, depression and anxiety-state (see also Foa & Meadows, 1997; Marks et al., 1998). Improvers were defined as participants who showed at the end of treatment (a) at least a 50% decline in PTSD symptoms compared with pretreatment symptoms and (b) scores below the posttreatment means for our sample on the SCL-!%depression (M = 30.0) and STAI-state (M = 44.4).

Results

D e m e n t Improvement

Of the 34 completers, 21 participants (61.8%) had improved. Despite the improvement. three of them still had PTSD-diagnosis at the end of the treatment. Thirteen participants (38.2%) had not improved, and all of them still had a PTSD-diagnosis at the end of treatment. In Table 1, the PTSD, depression and state-anxiety symptoms for improved and nonimproved participants and for participants who dropped out are shown. Trends towards significance were found for differences between improvers, nonimprovers, and dropouts with regard to pretreatment scores for PTSD symptoms, F(2,42) = 2.47, p = .lo, and depression, F(2.42) = 2.78, p = .07.

Participants in the improved group showed a significant decrease in PTSD symptoms, t(20) = 12.26, p c .001, depression, r(20) = 4.38, p c .001, and state- anxiety, r(20) = 6.05, p < .001. Nonimproved participants displayed a significant decrease in PTSD symptoms, r ( 12) = 2.52, p < .05, but no pre- to posttreatment differences in depression or state-anxiety.

Patterns of Subjective Anxiety Levels

Figure 1 shows the patterns of anxiety levels during the treatment. Seven of the 1 1 participants that dropped qut of the study dropped out early in treatment, that is, before the second exposure session. Therefore, only SUDs from the first exposure session were included in this group's analyses.

Fear Activation

In Table 2, fear activation and habituation patterns are depicted. Both improved and nonimproved participants as

'hble 1. Symptom Seventy (PTSD, Depression. and State-Anxiety) for Improvers. Nonimprovers, Dropouts. and Total Grouu

Improvers Nonimprovers Dropouts Total group

N M (SO) N M (SD) N M (SD) N M (SD) ~~~~~~~~~~

PSS-SR Pretreatment 21 23.8 (7.9) 13 30.2 (8.3) 1 1 27.5 (9.4) 45 26.5 (8.7) Posttreatment 21 4.3 (3.8) 13 25.1 (9.1) - - 34 15.7 (12.7)

Pretreatment 21 34.4 (12.8) 13 44.2 (12.3) I 1 42.5 (13.4) 45 39.2 (13.3) 34 30.2 (13.4)

Pretreatment 21 52.1 (11.7) 13 59.9 (11.2) 1 1 56.8 (10.5) 45 55.5 (11.6) Posttreatment 21 32.7 (9.1) 13 59.2 (11.4) - - 34 44.5 (17.0)

SCL-90-depression

Posttreatment 21 22.2 (8.3) 13 41.8 (12.0) - - STAI-state

Nore. PSS-SR = PTSD Symptom Scale Self-Report; SCL90-R = Symptom Checklist Revised; STAI = State Anxiety Inventory.

/ /

/

9 .4

\ \

ans


Table 2. Fear Activation, Within-Session Habituation, and Between-Session Habituation Patterns Based on SUDS Ratings During Exposure Therapy

Improvers Nonimprovers ~ P o u B

N M (SD) N M (SD) N M (SD)

Fear activation Mean (S I ) Peak (SI) Peak minus start (SI)

Within-session habituation Peak minus end (Sl) Mean peak minus end (home) Peak minus end (S2)

Mean (SI) minus mean (S2) Peak (S1) minus peak (home) Peak ( S l ) minus peak 6 2 )

Number of times listened to tape

Between-session habituation

Homework compliance

21 5.8 (1.6) 13 6.9 21 8.2 (1.5) 13 8.7 21 3.8 (2.9) 13 I .9

21 3.5 (2.5) 13 2.5 18 2.3 (2.1) 12 0.8 20 2.4 (1.9) 13 3.2

20 1.3 (1.9) 13 -0.1 18 2.0 (2.0) I2 0.3 20 2.1 (2.1) 13 -0.1

18 4.3 (1.0) 12 4.7

(1.4) I 1 6.2 (1.9) ( 1 .O) I I 8.0 (1.7) ( I .8)* I 1 3.5 (2.0)

(2.5) 1 1 1.8 (2.6) (0.7)"' - -

( I .5)" - - ( I .4)** - - (1.3)**** - -

(0.5)

- - (2.4)

- -

Note. S indicates session number. * p < .lo. * *p < .05. ***p < .01. ****p c .001.

well as dropouts did not significantly differ in mean and peak SUD ratings during S1. ANOVA showed a trend in difference in fear activation in S1, F(2,42) = 2.60, p = .09. Contrast tests revealed that improved participants showed a greater increase in anxiety levels during S 1 than did nonimproved participants, r(32) = -2.14, p < .05. Further inspection of the data showed that patient groups significantly differed in their initial anxiety level. Nonimproved participants exhibited significantly higher anxiety levels (M = 6.7, SD = 2.3) at the start of the session than did dropouts (M = 4.5, SD = 2.6) and improved participants (M = 4.4, SD = 3.1), F(2,42) = 3.19, p < .05.

W~hin-Session Habituation

No significant differences between patient groups were found for within-session habituation in S1 and S2. A significant effect was, however, found for habituation at home. Improvers showed significantly more habituation within their exposure sessions at home than did nonimprovers, r(28) = -2.04, p < .01.

Between-Session Habituation

Improvers showed a significantly greater decline in mean SUD ratings, t(31) = -2.20, p < .05, and peak SUD ratings, r(31) = -3.48, p < .001, between S1 and S2 than did nonimprovers. In addition, improvers had achieved more habituation than nonimprovers between S 1 and exposures at home, r(28) = -2.06, p < .05.

Homework Compliance

No significant differences were found between improvers and nonimprovers with regard to the mean number of times they listened to the tape at home. Of the improvers, 47.3% complied with the instruction to listen to the tape five times at home, as against 53.8% of the nonimprovers.

Partial Correlntions

Since the improved and nonimproved patient groups at pretreatment assessment tended to differ in PTSD and depression symptom severity, found differences in patterns of fear activation and habituation may be related to differences in the severity of symptoms at the start of the treatment instead of reflecting improvement per se. Fur- thermore, the used end-state functioning criterion does not correct for pretreatment symptom severity. To inves- tigate the influence of pretreatment symptom seventy in relation to patterns of fear activation and habituation on posttreatment symptom severity, partial correlations were computed for the total group of completers (n = 34). Cor- relations were computed between all variables showing significant differences between the improvers and nonimprovers (initial level of anxiety S 1, within habituation (Home), between habituation (Peak S 1-S2), and between habituation (Peak S 1-Home) and PTSD symptom severity at posttreatment assessment, while PTSD symptoms and depression at pretreatment measurement were partialled out. The results are presented in Table 3. It was found that Habituation between S 1 and S2 was significantly related to


Table 3. Correlations Between Fear Activation and Habituation patterns and Posmeatment PTSD Symptom Severity, With and Without Partiallina out Pretreatment PTSD Svmotoms and Depression (N = 34)

Variable r Partial r

Initial level of anxiety SI .3 1 .24 Within habituation (home) -.31 -.20 Between habituation (peak S 1 4 2 ) -.38*' -.36** Between habituation (peak SI-home) -.36' -.31 ~~ ~~ ~ ~~ ~

Nore. S indicates session number. ' p c .lo. * * p < .05.

PTSD symptom severity at posttreatment evaluation and that this relation was still significant after controlling for pretreatment PTSD and depression symptom severity.

Discussion

This study demonstrated that patterns in subjective anxiety level can be used to detect, at an early stage in the treatment, those PTSD patients unlikely to improve with prolonged exposure. With regard to fear activation, it was found that mean and peak SUDS ratings in the first exposure session did not significantly differ between improvers, nonimprovers and dropouts. However, nonimproved patients reported higher levels of anxiety at the beginning of the first session, indicating a high level of anticipatory anxiety. This finding is consistent with a study into patterns of anxious arousal during exposure in social phobics (Coles & Heimberg. 2000). Social phobics who were already showing high levels of anxiety at the start of the exposure were less likely to improve than were patients showing mild anxiety.

One could argue that the anxiety experienced by improvers during the exposure is directly related to the feared stimuli (i.e.. the traumatic memories). These patients thus fulfil the necessary condition postulated for successful treatment: adequate activation of the fear structure as a proposition to change pathological elements in that structure (Foa & Kozak, 1986). In patients who are already showing high anxiety levels at the beginning of the exposure, the fear may be more anticipatory in nature. Al- though during the session eventually the same peak in subjective anxiety is achieved, this activated anxiety may not be directly related to the feared stimuli, which may result in a less complete revivification of the traumatic memories during the imaginal exposure. Consequently, no optimal access to the traumatic memory can be gained, thus preventing pathological fear structures from being modi- fied. Alternatively, high levels of anxiety before the start of the exposure session may reflect an increase in intru- sive recollections of the traumatic event. Future research

could focus on high levels of anxiety at the beginning of the exposure session in relation to the efficacy of the exposure.

In accordance with the Foa and Kozak (1986) theory and previous research (Jaycox et al., 1998), between- session habituation differed significantly between improved and nonimproved patients. Improved patients showed significantly more habituation between the first and second exposure sessions. In addition, they showed more habituation between the first session and the exposures at home. Within-session habituation during the exposure sessions, on the other hand, was not related to treatment outcome. This finding is, however, consistent with previous studies in which between-session habituation, but not within-session habituation, was found to be related to treatment outcome in both obsessive-compulsive disorder patients (Foa et al., 1982; Kozak et al., 1988) and PTSD-patients (Jaycox et al.. 1998).

An interesting finding with regard to within-session habituation is that improved patients showed significantly more habituation within the repeated self-exposures at home than did nonimproved patients. Contrary to expec- tations, these differences could not be explained by differences in the number of self-exposures. In fact, nonimprovers were at least as compliant with the self-exposure assignments at home as were improvers. It would be worthwhile to study the role of the self-exposures in the habituation process more closely in future research.

The finding that between-session habituation is a better indicator of improvement than is within-session habituation may have implications for the duration of the sessions. The duration of the exposure therapy for PTSD was set at 45-60 min per session (prolonged), based on the assumption that within-session habituation was necessary to ensure good treatment results (Foa & Kozak, 1986). Thus far, however, there is very little to suggest that within-session habituation is a necessary condition for successful treatment outcome. Furthermore, given the importance of within-session habituation at home, it may be that it is the frequency of exposure to a feared stimulus rather than the duration of the exposure that is important. To study the optimal duration and frequency of exposure, both in the treatment sessions and at home, future research could compare prolonged versus brief exposure and frequent versus infrequent exposure in PTSD patients in relation to habituation patterns (both during sessions and during exposures at home) and treatment outcome.

Despite the fact that, at pretreatment assessment, there were trends toward significant differences between the improved and nonimproved groups in terms of PTSD symptom severity and depression, the relationship


between habituation and treatment outcome remained significant after controlling for those variables. Although pretreatment symptom severity is known as a relatively stable predictor of treatment success (e.g., Van Minnen, Amtz, & Keijsers, 2002). this study has shown that habituation patterns early in treatment can also have a unique relationship with treatment outcome.

It needs to be noted that our study had a limitation in that the sample was relatively small and, more importantly, quite diverse with regard to gender and trauma history. Fu- ture research should attempt to replicate these findings in more extensive groups. It would also be worthwhile to include physiological measures of anxiety during exposure, because studies looking at anxiety treatment outcome in general (Foa & Kozak, 1986; Foa & McNally, 1996) and PTSD in particular (Griffin, Nishith, Resick, & Yehuda, 1997) have indicated that physiological measures have ad- ditional predictive power over subjective ratings.

In sum, our results show that relationships between process variables, particularly the degree of between- session habituation, and treatment outcome exist, even when pretreatment PTSD and depression symptom severity are controlled. It is suggested that this between-session habituation is achieved by both adequate fear activation (i.e., fear evoked by the feared stimulus), and frequent ex- periences of habituation during repeated exposures to the same feared stimulus.

Unfortunately, because of the large number of early dropouts, not all the analyses of anxiety patterns could be performed for this group. Still, based on the anxiety patterns in the first exposure session, dropouts could not be distinguished from patients who had completed the treatment in terms of the degree of fear activation and within-session habituation. This indicates that these patients probably had reasons for not completing the therapy other than the degree of experienced anxiety during the first exposure. Nevertheless, this issue warrants more research.

Future research may focus on the question whether and in what way treatment prognosis could be made more accurate for those patients unlikely to improve. The course of treatment across treatment sessions can be predicted by using patient profiling (Lutz, Martinovich, & Howard, 1999). This would allow the therapist to detect at an early stage those patients unlikely to improve or those that are likely to deviate from the successful treatment course. Some gains could be made by investigating whether treatment outcome could be improved by offering such patients an alternative evidence-based treatment programme, such as cognitive therapy. Also, the prolonged exposure treatment could be adjusted for those patients who are unlikely to improve, for instance, by using methods aimed

at decreasing the initial anxiety level, or by offering these patients more (frequent) treatment sessions.

Acknowledgments

The authors thank Suzanne Kaenen for her help with the data collection, Margaret Jones for her helpful com- ments, and Peter Desain for his stimulating support.

References

American Psychiatric Association. (1987). Diagnostic and staristical manual of mental disorders (3rd ed., revised). Washington, DC: Author.

American Psychiatric Association. (1994). Diagnostic and statisrical manual of mental disorders (4th edn.). Washington, DC: Author.

Arrindell, W. A,. & Ettema, J. H. M. (1986). SCL-90: Handleiding bij een multidimensionele psychoputhologie-indicator [ SCL-90: Man- ual of a multidimensional psychopathology indicator]. Lisse: Swetz & Ztitlinger.

Borkovec, T. D. (1972). Effects of expectancy on the outcome of system- atic desensitization and implosive treatments for analogue anxiety. Behavior Therapy. 3, 2 9 4 .

B0rkovec.T. D.. & Sides, J. (1979). The contribution of relaxation and expectancy for fear reduction via graded imaginal exposure to feared stimuli. Behaviour Research and Therapy, 17, 529-540.

Boudewyns. P. A., & Hyer. L. (1990). Physiological response to combat memories and preliminary treatment outcome in Vietnam veteran PTSD patients treated with direct therapeutic exposure. Behavior Therapy, 21. 63-87.

Coles, M. E., & Heimberg, R. G. (2000). Patterns of anxious arousal during exposure to feared situations in individuals with social phobia. Behaviour Research and Therapy. 38# 405424.

Cooper, N. A.. & Clum. G. A. (1989). lmaginal flooding as a supple mentary treatment for PTSD in combat veterans: A controlled study. Behavior Therapy, 20, 38 1-39 I .

h a , E. B., & Chambless, D. (1978). Habituation of subjective anxiety during flooding in imagery. Behaviour Research and Therapy, 16.

Foa. E. B.. Dancu, C. V.. Hembree. E. A.. Jaycox, L. H., Meadows. E. A,, & Street, G. P. ( 1999). A comparison of exposure therapy, stress in- oculation training, and their combination for reducing posttraumatic stress disorder in female assault victims. Journal of Consulting and Clinical Psychology. 67, 194-200.

Foa, E. B., & Kozak, M. J. (1986). Emotional processing of fear: Expo- sure to corrective information. Psychological Bullerin, 99. 20-35.

Foa. E. B., & McNally, R. J. (1996). Mechanisms of change in exposure therapy. In R. Rapee (Ed.). Current controversies in the amiefy disorders (pp. 329-343). New York: Guilford.

Foa. E. B.. & Meadows, E. A. (1997). Psychosocial treatments for posttraumatic stress disorder: A critical review. Annual Review of Psy- chology. 48, 449480.

Foa, E. B., Grayson. J. B., & Steketee, G. (1982). Depression, habituation and treatment outcome in obsessive-compulsives. In J. Boulougouris (Ed.). Practical applications of learning theories in psychiarry (pp. 129-142). New York: Wiley.

Foa, E. B., Riggs, D. S.. Dancu, C. V.. & Rothbaum, B. 0. (1993). Relia- bility and validity of a brief instrument for assessing posttraumatic stress disorder. Journal of Traumatic Stress. 6. 459-473.

Foa. E. B., Riggs, D. S., Massie. E. D.. & Yarczower. M. (1995). The impact of fear activation and anger on the efficacy of exposure treatment for posttraumatic stress disorder. Behavior Therap.v, 26. 487-499.

Foa, E. B., Rothbaum, B. 0.. Riggs, D. S., & Murdock, T. B. (1991). Treatment of posttraumatic stress disorder in rape victims: A

391-399.


comparison between cognitive-behavioral procedures and coun- seling. Journal of Consulting and Clinical Psychology, 59, 715- 723.

Grayson, 1. B.. Foa, E. B.. & Steketee. G. (1982). Habituationduring exposure treatment: Distraction versus attention-focusing. Eehaviour Research and Therapy, 20.323-328.

Griffin, M. G.. Nishith. I?, Resick. P. A.. & Yehuda, R. (1997). Integrating objective indicators of treatment outcome in posttraumatic stress disorder. In R. Yehuda & A. McFarlane (Eds.), Psychobiology of posttraumatic stress disonfer (pp. 3 8 8 4 ) . New York: New York Academy of Sciences.

Hiller. W.. Zaudig. M.. & Mombour, W. (1990). Munich Diagnostic Checklists fo r DSM-Ill-R and ICD-lo. MUnchen: Logomed.

Jaycox. L. H.. Foa, E. B.. & Morral, A. R. ( 1998). Influence of emotional engagement and habituation on exposure therapy for PTSD. Journal of Consulting and Clinical Psychology, 66. 185-192.

Keane, T. M., Fairbank, J. A,, Caddell, J. M., & Zimering, R. T. (1989). Implosive (flooding) therapy reduces symptoms of PTSD in Vietnam Veterans. Behavior Therapy, 20, 245-260.

Kozak. M. J., Foa. E. B.. & Steketee, G. (1988). Process and outcome of exposure treatment with obsessive-compulsives: Psychophysio- logical indicators of emotional processing. Behavior Therapy. 19. 157-169.

Lang. P. 1. (1979). A bio-informational theory of emotional imagery. Psychophysiology, 16.495-5 12.

Lang, P., Melamed, B., & Han, J. D. (1970). A psychophysiological ana- lysis of fear modification using automated desensitization. Journal o f A h n o m 1 Psychology. 31. 22&234.

Lutz, W., Martinovich. Z.. & Howard. K. 1. (1999). Patient profiling: An application of random coefficient regression models to depicting the response of a patient to outpatient psychother- apy. Journal of Consulting and Clinical Psycho1og.v. 67, 571- 577.

Marks, 1.. Lovell. K., Noshirvani. H., Livanou, M.,&Thrasher, S. (1998). Treatment of posttraumatic stress disorder by exposure andor

cognitive restructuring. A conmlled study. Archives of General Psychiatry, 55, 3 17-325.

Nune, J. S . . & Marks. 1. M. (1975). Passive and participant modeling in exposure treatment of obsessive-compulsive neurotics. Archives of General Psychiarry, 32.933-996.

Pitman, R. K.. Om, S. P., Altman. B.. Longpre. R. E., Poire. R. E., Macklin, M. L.. et al. (1996). Emotional pmessing and outcome of imaginal flooding therapy in Vietnam veterans with chronic posttraumatic stress disorder. Comprehensive Psychiatry. 37, 409-418.

Rachman, S. (1980). Emotional processing. Eehaviour Research and Therap.v. 14. 349-355.

Spielberger. C. D., Gorsuch, R. L.. & Lushene. R. E. (1970). Manual for the State-Trair Amiefy hventory. Palo Alto, CA: Consulting Psychologists Press.

Stem, R. S., & Marks, 1. M. (1973). Brief and prolonged exposure: A comparison in agoraphobic patients. Archives of General Psychia- try, 28,27&276.

Tarrier, N., Pilgrim, H.. Sommerfield. C., Faragher, B.. Reynolds, M.. Graham, E., et al. (1999). A randomized trial of cognitive therapy and imaginal exposure in the treatment of chronic posttraumatic stress disorder. Journal of Consulting and Clinical Psychology. 67.

Van der Ploeg. H. M., Defares. P. B., & Spielberger. C. D. (1980). Han- dleiding bij de ZelfEeoordelings Vragenlijst [Manual of the Dutch Version of the STAI]. Lisse: Swetz & Zeitlinger.

Van Minnen, A.. Amu, A., & Keijsers, G. P. J. (2002). Prolonged exposure in patients with chronic PTSD: Predictors of treatment outcome and dropout. Eehaviour Research and Therapy, 40,439-457.

Watson, J. P.. Gaind. R.,& Marks, 1. M. (1972). Physiological habituation to continuous phobic stimuli. Eehaviour Research and Therapy, 10,

Watson, J. P., & Marks, 1. M. (1971). Relevant and irrelevant fear in flooding: A crossover study of phobic clients. Behavior Therapy.

13-18.

269-278.

2, 275-293.

Documents

Fear activation and habituation patterns as early process predictors of response to prolonged exposure treatment in PTSD