German Journal of Psychiatry

SOMATOFORM DISORDER AND IMPLICIT MEMORY BIAS

R. Ott, R. Spielberg, and O.B. Scholz
Department of Psychology, University Bonn

THEORETICAL BACKGROUND

Cognitive theories of somatoform disorders posit information processing biases that influence the maintenance, and perhaps the etiology, of somatization disorders and hypochondriasis (e.g. Barsky, 1992; Salkovskis & Clark, 1993), which are comparable with the same empirically well funded phenomenons in panic disorders.

Barsky and coworkers argue, that somatosensory amplification is one central pathological mechanism involved in somatoform disorders. Furthermore, this bodily hypervigilance is suppossed to be based on a more general process of selective attention to unpleasant events.

However, it is worth noting that this theoretical assumption about a more general process of selective processing not only concerning interoception is not based on experimental data. Aim of this study was to analyse cognitive processes for threatening auditory word material in somatoform disorders.
 
METHOD

Subjects

Experiment 1: Ss with somatization syndrome according to the Somatic Symptom Index (SSI-4/6, n=14) versus healthy control Ss (n=14, analogue study, c.f. Ott & Scholz, 1999)

Experiment 2: Ss with somatoform disorders according to DSM-IV (MCDL, n=28) versus healthy Ss (n=25)
 

Table: Description of samples
Experiment 1
 
SSI 4/6
Healthy
Sex
Age
SOMS *
Anxiety
Depression
10 f, 4 m
24.79 ± 4.27
10.00 ± 5.96
2.21 ± 1.85
3.00 ± 3.11
7 f, 7 m
25.07 ± 4.50
0.93 ± 1.07
1.71 ± 2.13
3.57 ± 2.24
Experiment 2
 
Patients
Healthy
Sex
Age
SOMS *
Anxiety
Depression
17 f, 11 m
44.48 ± 9.16
15.31 ± 4.25
2.48 ± 2.05
2.52 ± 1.11
14 f, 11 m
42.43 ± 7.38
1.89 ± 1.37
2.08 ± 1.31
2.62 ± 1.79
Notes: State anxiety and depressive complaints were assessed through AN-DE ("Angst-Depressions-Screening"), somatic complaints through SOMS ("Screening for somatoform disorders"), * = p < .01

Procedure

During learning phase subjects heard a random series of neutral and threat words and were instructed to build a sentence (incidental learning). 

Memory for this prior exposure was then tested by a lexical decision task involving the recognition of stimuli (words and nonwords), which were acoustically presented masked with white noise. Half of the stimuli in the test phase have already been learned ("old" items), half of them not ("new" items).

Material

Target Words: Two lists of stimuli (neutral words vs. body-related threat words) each consisting of 60 words and 60 nonwords were used. Words were collected from a German norm data study (Ott & Scholz, 1998), which provides ratings for familiarity and threat. Both lists were matched for number of syllables and ratings of familiarity, but differ significantly in their ratings of threat.

Masking of stimuli: Items were masked by white noise with a constant signal-noise ratio of -17dB. (narrow band masking, Ott & Curio, 1999).

Data Analysis

Priming in lexical decision task is revealed (1) when subjects are more likely to recognize an "old" word as word than a "new" word and (2) when subjects are more likely to recognize an "old" nonword falsely as word than a "new" nonword. Resulting frequencies were analyzed using a modified Process Dissociation Procedure (c.f. Jacoby, 1998) which incorporates a guessing parameter (Ott, Curio & Scholz, 2000) and allows to estimate parameters for:

  • conscious discrimination
  • priming words
  • priming nonwords
  • response bias
Four ANOVAs, one for each of these parameters, with the between-subject variable group (somatoform vs. control) and the within-subject variable stimulus content (neutral vs. threat) were run to analyze a possible memory bias.

 

RESULTS

Experiment 1

Conscious discrimination, response bias, priming nonwords: ANOVAs revealed no significant stimulus content and group main effect and no significant stimulus content ´ group interaction effect.

Priming words: ANOVA revealed no significant main effects, neither for stimulus content nor for group, but a significant stimulus content ´ group interaction effect [F(1, 26) = 5.00, p < .05]. For the SSI 4/6 group, the threat words were better primed than the neutral nonwords, which led to a higher hit rate for "old" threat words. Control subjects did not show enhanced priming for threat words (see fig.1).


Figure 1:Priming for words and nonwords in SSI 4/6 
subjects and healthy control subjects (Experiment 1)
Experiment 2

Conscious discrimination, response bias, priming words: ANOVAs revealed no significant stimulus content and group main effect and no significant stimulus content ´ group interaction effect.

Priming nonwords: ANOVA revealed no significant main effects, neither for stimulus content nor for group, but a significant stimulus content ´ group interaction effect [F(1, 51) = 6.25, p < .05]. Within the patient group, the threat nonwords were better primed than the neutral nonwords, which led to a higher rate of false alarms for nonwords built out of threat words. Control subjects did not show enhanced priming for threat nonwords (see fig. 2).


Figure 2: Priming for words and nonwords in Patients with 
Somatoform Disorders and healthy control subjects (Experiment 2).
DISCUSSION

In two experiments subjects with somatoform symptoms, but not healthy control subjects, showed biased priming towards threatening stimuli. This finding suggests that somatization disorder may be characterized by a memory bias for threat and is well in line with theoretical assumptions about the etiology of somatization.

Information processing paradigms and models have recently often been used to examine and describe the cognitive processes associated with emotional disorders (see Williams et al., 1997) and have produced distinguishable patterns of results. Depression seems to affect the controlled aspects of information processing, whereas anxiety affects the automatic aspects of encoding and retrieval.

Somatoform disorders seem to be one disorder which is closely related to anxiety. On the level of diagnosis some recently published studies could show high comorbidity of anxiety and somatization respectively somatoform disorders. Within this framework, the current findings support the view that somatization might be on a cognitive level associated with anxiety. Further studies should aim to replicate such findings and to further describe this bias especially in delimitation to anxiety disorders.
 
REFERENCES

Barsky AJ. Amplification, somatization, and the somatoform disorders. Psychosomatics 1992; 33:28-34

Ott R, Curio I. Masking of complex sound - technical notes for the realization of constant signal-noise-ratio. Perc Motor Skills 1999; 89:137-144

Ott R, Curio I, Scholz OB. Implicit memory for auditorily presented threatening stimuli: A Process- Dissociation approach. Perc Motor Skills 2000; 90:131-146

Ott R, Scholz, OB. Wortnormen der Bedrohlichkeit und Bekanntheit für 197 körperbezogene deutsche Substantive [Norm data for degree of threat and familiarity of 197 body-related german nouns]. Sprache Kognit 1998; 17: 214-223

Ott R, Scholz, OB. Memory bias in somatization: A pilot study. Submitted for publication 1999

Salkovskis PM, Clark, DM. Panic disorder and hypochondriasis. Special issue: Panic, cognitions and sensations. Adv  Behav Res Ther 1993; 15:23-48

Williams JMG, Watts FN, MacLeod C, Mathews, A. Cognitive psychology and emotional disorders (2nd ed.). Chichester: Wiley 2000


Author's Note
Ralf Ott, Dipl.-Psych.
Department of Psychology
Roemerstrasse 164
D-53117 Bonn
Germany

Email: ralf.ott@uni-bonn.de


Supported by grant Scho-327/5-1 from Deutsche Forschungsgemeinschaft

Poster presented at 29th Annual Congress of the EABCT, Dresden, September 1999.

For citing this paper please follow the APA standard for referencing online documents in scientific publications: Ott, R., Spielberg, R. & Scholz, O.B. (2000). Somatoform disorders and implicit memory bias. German Journal of Psychiatry [On-line], 3. Available: http://www.gwdg.de/~bbandel/gjp-poster-ott.htm .