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Schizophrenia Research

‘Jumping to conclusions’ and delusions in psychosis: Relationshipand response to treatment

Mahesh Menon a, Romina Mizrahi a,b, Shitij Kapur a,b,c,⁎

a Schizophrenia Program and PET Centre, Centre for Addiction and Mental Health, Toronto, Canadab Department of Psychiatry, University of Toronto, Toronto, Canada

c Division of Psychological Medicine and Psychiatry, Institute of Psychiatry, London, UK

Received 16 April 2007; received in revised form 15 August 2007; accepted 20 August 2007Available online 25 September 2007

Abstract

‘Jumping to conclusions’ (JTC) on probabilistic reasoning tasks has been shown to be related with delusions in schizophrenia.However, whether JTC is merely correlated with, moderate or mediate delusions is not known. Further, it is unclear howantipsychotics affect JTC and its relationship to delusions. We examined the effect of treatment on JTC in a sample of patients(N=19) who were initiated on treatment and followed. Two versions of the task were used— the ‘beads’ version of the task and anemotionally salient version. Within two weeks of treatment, we found an increase in the number of trials to decision on theemotionally salient version and a reduction in intensity of psychotic symptoms and delusions (measured by the change on P1 andPANSS-P scores). While, these two measures, or changes in these measures, showed no reliable correlation, the baselineperformance on the emotionally salient version of the task helped predict patients who would show improvements in their PANSS-P and global PANSS scores in response to medication. The findings suggest that JTC might moderate the effects of treatment onsymptomatology, but it does not mediate the treatment induced reduction in delusional intensity.© 2007 Published by Elsevier B.V.

Keywords: Schizophrenia; Delusions; Probabilistic reasoning; JTC; Longitudinal study; Medication

1. Introduction

Cognitive theories of delusions provide a linkbetween the biological and phenomenological explana-tions of delusions (Garety and Freeman, 1999) andmight serve as mechanistic explanations of howaberrations in biochemistry seen in schizophreniacould lead to symptomatology. One such cognitive

⁎ Corresponding author. Centre for Addiction and Mental Health, 33Russell St., Toronto M5S 2S1, Canada. Tel.: +1 416 979 6890; fax: +1416 260 4164.

E-mail address: Shitij_Kapur@camh.net (S. Kapur).

0920-9964/$ - see front matter © 2007 Published by Elsevier B.V.doi:10.1016/j.schres.2007.08.021

theory is the ‘probabilistic reasoning bias’ theory, or as itis currently conceptualized, the ‘data gathering bias’theory, developed by Garety and co-workers (Garetyand Freeman, 1999; Garety et al., 1991). It suggests thatunder conditions of uncertainty, people with delusionsuse less information to arrive at a decision, a ‘jumping toconclusions’ (JTC) reasoning style. The JTC responsepattern has been seen in multiple studies of deludedpatients with schizophrenia (Dudley et al., 1997a,b;Garety et al., 1991; Menon et al., 2006; Moritz andWoodward, 2005) and those with schizophrenia spec-trum disorders such as delusional disorder (Fear et al.,1996; Fear and Healy, 1997). Besides patients with

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psychotic symptoms, the JTC response pattern has alsobeen found in first degree relatives of schizophreniapatients (Van Dael et al., 2006), in subjects who scorehigh on a measure of schizotypy (Colbert and Peters,2002), and in subjects at a high risk for developingpsychosis (Broome et al., 2004).

The Broome et al. (2004) study suggests that thisresponse pattern might be a vulnerability factor in thedevelopment of psychosis. Other studies (Menon et al.,2006; Moritz and Woodward, 2005; Mortimer et al.,1996) have found that this response pattern is seen bothin schizophrenia patients with and without currentdelusions. A recent longitudinal study (Peters andGarety, 2006) has suggested that this is a stableimpairment, which did not normalize after remission ofsymptoms. While these studies suggest that this ‘datagathering bias’ might be a vulnerability factor indelusion formation and persist after the resolution ofdelusions, there is some evidence (Brankovic andPaunovic, 1999; Menon et al., 2006; Moritz andWoodward, 2005) indicating that patients might showa partial remission, suggesting that actively deludedpatients show a higher level of JTC than currently non-deluded patients.

However, few longitudinal studies have examinedthe relationship between task performance during thecourse of symptom remission. Brankovic and Paunovic(1999) carried out a longitudinal study and comparedthose patients who remitted to those who stayedpsychotic. They used the probability estimates method,and found that patients who stayed psychotic hadstronger responses to confirmatory and disconfirmatoryresponses than subjects who remitted. However, theydid not explore the relationship between changes inspecific symptomatology and performance on the JTCtask but instead focused on the violations from theBayesian norms demonstrated by the two groups. Petersand Garety (2006) examined a group of patients firstwhen they were deluded and then again when theirsymptoms were in remission. They found that whiletheir probability estimates normalized, the JTC biaspersisted in remission.

Thus, the question of how the probabilistic reasoningbias is connected to the maintenance and resolution ofdelusions, and the nature of the relationship betweenchanges in the JTC response pattern and changes indelusional symptomatology is yet to be determined. Theprimary treatment for schizophrenia patients remainspharmacological. Therefore, any study looking atchanges in symptomatology should factor in theresponse to medication, which might be affecting theJTC response pattern as well. The Peters and Garety

(2006) study used a large sample of patients, but many ofthem were chronic patients. The ideal method todisentangle the effects of medication and the relationshipbetween changes in JTC and changes in symptomatol-ogywould be to examine first episode patients, who havenot been medicated and follow them over the course oftheir pharmacological treatment. To the best of ourknowledge, this has never been previously attempted.

A number of possible relationships might existbetween JTC, medication and delusions. Using theframework developed by Baron and Kenny (1986), thecognitive processes underlying JTC might act as me-diators or moderators. This framework has been furtherdeveloped by Kraemer et al. (2002), who use the sameconceptual basis to create an operational framework toidentify factors influencing the efficacy of therapeuticchange in clinical trials. According to their model,moderators influence the outcome of treatment, and thusspecify for whom and under what conditions thetreatment works, while mediators are directly involvedin the causal chain. Thus conceptually, “moderatorsidentify on whom and under what circumstancestreatments have different effects, while mediatorsidentify why and how treatments have effects” (Kraemeret al., 2002). If the cognitive processes underlying theJTC response pattern acted as moderators, thenperformance on the probabilistic reasoning task atbaseline (or prior to the onset of pharmacotherapy)would serve to predict the outcome of medication onsymptom remission (Kraemer et al., 2002). If this werethe case, then we expect to see an association betweenbaseline performance on the probabilistic reasoning taskand subsequent improvement in symptomatology. Al-ternatively, if JTC is causally involved in the formationor maintenance of the delusion, it might mediate therelationship between medication and symptom remis-sion. If this were the case, then we would expect that thechanges in symptomatology that occur as a result of thepharmacotherapy would correlate with change inperformance on the probabilistic reasoning task (Krae-mer et al., 2002). A third possibility is that thephenomenon (JTC) and the delusions might both bedownstream consequences of simpler cognitive process-es or biochemical abnormalities co-occurring as a part ofthe illness, but not causally related to one another.

We chose to explore the changes in the JTC responsepattern in time and its association with delusionalsymptoms by longitudinally following a sample of firstepisode patients over four weeks following the begin-ning of antipsychotic treatment. Two versions of the taskwere used — the first is the neutral and somewhatabstract ‘beads’ version of the task. The second is a more

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naturalistic and emotionally salient (ES) version of thetask. Earlier studies by Dudley et al. (1997a) and Youngand Bentall (1997) have suggested that the use of selfreferent and emotionally salient material heightens theJTC bias.

2. Methods

2.1. Participants

Nineteen patients were recruited from the inpatientand outpatient services of the Schizophrenia Program atthe Centre for Addiction and Mental Health (CAMH),Toronto. Five other subjects declined to participate inthe study. All subjects were recruited using the ResearchRegistry maintained by the Schizophrenia Program atCAMH and gave written informed consent. The studyand the recruitment procedures were approved by theResearch Ethics Board of CAMH. Sixty three percent ofthis group (12/19) was neuroleptic naïve at thebeginning of treatment, while the others were startedon atypical antipsychotic medication at most 48 h beforethe first interview and had been drug free at least for2 weeks prior to inclusion in the study. Six patients werehospitalized, while the other thirteen patients weretreated on an outpatient basis. Participants were testedafter two and four weeks on medication. All diagnoseswere established from the treating psychiatrist using theDSM-IV criteria, and verified by using the MiniInternational Neuropsychiatric Interview (MINI-Lecrubier et al., 1997). Symptom ratings were deter-mined using the Positive and Negative Symptom Scale(PANSS-Kay et al., 1987), which was administered toall participants at each testing session. These scales wereadministered by a psychiatrist (RM). Further informa-tion regarding the pattern of change of this first episodecohort can be seen in Mizrahi et al. (2006).

2.2. Tasks

Two versions of the probabilistic reasoning task wereused, both adapted from Dudley et al. (1997a). In theneutral version of the task, two jars containing white andblue beads in a 60:40 ratio were used. The ‘mostly white’jar contained 60 white and 40 blue beads, while the‘mostly blue’ jar contained 60 blue and 40 white beads.Participants were shown the two jars and told that thebeads would be drawn from one of the jars randomly.The two jars were then removed from view, and thebeads were drawn in a pre-determined sequence fromone of the two jars. Following each draw, participantseither had to request another bead or say that they had

arrived at a decision. When they had arrived at adecision, they were queried as to which jar they felt thebeads were being drawn from.

The emotionally salient version of the task hadsimilar requirements, except that participants were toldto imagine that two surveys had been carried out about aperson. In each survey a hundred people were askedwhat they thought of this person. In one of the surveys,the ‘mostly good’ survey, 60 people made positivecomments about the person while 40 people madenegative comments, while the ‘mostly bad’ survey hadthe opposite ratio of 60 negative and 40 positivecomments. Positive and negative adjectives werepresented one at a time till the participants decidedwhether the results from the ‘mostly good’ or ‘mostlybad’ survey. The stimuli for this task were similar tothose used by Dudley et al. (1997a) and Menon et al.(2006). The tasks all used the same two sequences(sequence one — ABBABAABBBBABBBABAAB,sequence two — ABBAABBBAABABBABBBAB).

The numbers of draws to decision were taken as thevariable of interest. Fewer draws to decision indicates aJTC response pattern.

3. Results

Of the 19 patients included in this study, 14 patientshad a diagnosis of schizophrenia (79%), 1 patient wasdiagnosed with schizoaffective disorder (5%) and 4 withschizophreniform disorder (16%)). The mean age of thesample was 30.8 years (SD 12), mean IQ was 94 (SD 11)and the majority were male (14/19). 18/19 participantswere treated with atypical antipsychotics, while onepatient was treated with Loxapine. The mean chlor-promazine equivalent (CPZ) units (Bezchlibnyk-Butleret al., 2005) starting dose was 100.8 mg (S.D. 68.6).There were no differences between subjects on JTCperformance at baseline based on medication and therewere no significant correlations between performanceon the probabilistic reasoning tasks and CPZ units (all pvaluesN .31).

As can be seen in Table 1 and Fig. 1, following twoweeks of antipsychotic medication, there was a signi-ficant reduction in delusion intensity (PANSS item P1, T(d.f. 18)=3.62, pb .01) as well as PANSS Positive T((d.f.18)=7.32, pb .001), PANSS Negative (T(d.f. 18)=3.43,pb .01) and PANSS Total (T(d.f. 18)=8.42, pb .001).There was also an increase in the number of draws todecision on the emotionally salient version of the task(T(d.f. 16)=2.97, pb .01), but no change on the neutralversion of the task (T(d.f. 17)=0.49). Similarly, there wasa further significant reduction in symptoms between week

Table 1Change in symptoms and task performance between baseline andfollowing two and four weeks of medication

Measure Baseline Two weeks Four weeks

PANSS P1 (delusions item) 5.00(0.9)

4.47(0.9)⁎

3.94(0.9)⁎⁎

PANSS positive 24.78(3.0)

20.58(3.4)⁎⁎

17.47(3.2)⁎⁎

PANSS negative 18.47(5.2)

16.05(4.6)⁎

14.71(5.0)⁎⁎

PANSS total 86.68(9.8)

74.0(10.7)⁎⁎

64.59(10.6)⁎⁎

Neutral beads task(draws to decision)

3.33(2.9)

3.66(2.1)

4.00(2.1)

Emotionally salient version(draws to decision)

2.29(1.5)

3.94(2.4)⁎

3.62(2.5)⁎

Number of JTC responders+

(neutral task)6/19 4/19 2/19

Number of JTC responders+

(emotionally salient version)8/19 3/19 5/19

⁎pb .01 ⁎⁎pb .001 +JTC response-arriving at a decision after a singledraw.

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two and week four after onset of medication (PANSSP1 — T(d.f. 16)=3.50, pb .01; PANSS Positive —T(d.f. 16)=5.37, pb .01; PANSS Negative— T(d.f. 16)=2.31, pb .05), but no further increase in the number ofdraws to decision on either version of the task. At thebaseline visit, 6 of the 19 subjects (32%) arrived at adecision after just a single draw in the neutral condition,and 8/ 19 (42%) responded after a single draw inemotionally salient condition. This proportion decreasedin subsequent visits. By the second visit, only 4/19(21%)responded after a single draw on the neutral version, and3/19 (16%) responded similarly on the emotionally salientversion (see Table 1).

Thus, after four weeks of medication, all themeasures of psychopathology were significantly lowerthan baseline and week two measures, while the numberof draws to decision on the emotionally salient version(but not the neutral version) remained significantlyhigher than baseline, but not significantly higher thanthe number of draws to decision at week two.

In order to examine the mediator hypothesis, wecreated change scores — consisting of change inpsychopathology measures from baseline, and changesin number of trials to decision from baseline on thereasoning tasks1. There was no correlation betweenchange in delusional intensity or other symptom change

1 A correlation between the change scores would not, in itself, havebeen sufficient to demonstrate mediation. However, the correlationbetween change scores is the sine qua non of mediation and thus theabsence of a correlation rules out the possibility that JTC mediates therelationship between medication and symptom change.

scores and changes in the number of draws to decisionon either task (r=.06 for ES version, r=− .26 for neutralversion, all p valuesN .30).

To test the moderator hypothesis, we examined whetherperformance at baseline on the reasoning task helped pre-dict subsequent change in the symptomatology.We found astrong positive correlation between number of draws todecision at baseline on the emotionally salient version ofthe task, and subsequent change in PANSS-P score aftertwo weeks (r=0.69, pb .01) and four weeks of medication(r=0.56, pb .05). This relationship remained signifi-cant even after initial PANSS-P score had been covariedout (after two weeks, r=0.65, pb .01; after four weeks,r=0.51, p=.06). This indicates that those participants whodid not show the JTC response pattern at baseline hadgreater reduction in their positive symptoms following twoweeks of medication, while those participants showing aJTC response pattern showed less improvement in theirsymptoms after two weeks of medication. The associationbetween baseline performance on the ES version andchange in delusion ratings showed a similar trend, butfailed to reach statistical significance (r=0.33, p=.20).When we looked at the reductions in the overall PANSSscores, we found no clear association with trials to decisionafter two weeks of medication, but there was a correlationbetween improvement in overall PANSS scores and trialsto decision on the emotionally salient version, after fourweeks (r=0.62, p=.01), which was significant even afterinitial PANSS scores were covaried out (r=0.67, pb .01).

Fig. 1. Change in symptoms and task performance between baselineand following two and four weeks of medication. PANSS P1 gives therating of delusional intensity.

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4. Discussion

In the current study, we examined change inperformance on two versions of a probabilistic reasoningtask at baseline and following two and four weeks ofmedication in a group of first episode schizophreniapatients, who were either never medicated or had been offmedication for at least two weeks prior to testing.Antipsychotic medication reduced intensity of delusions,and overall positive and negative symptoms after twoweeks and a further significant decrease was seen afterfour weeks. There was no change in performance on theneutral version of the reasoning task over time. However,the number of draws to decision on the emotionally salientversion of the task increased after two weeks ofmedication and then leveled out.

We found no correlation between changes in taskperformance and changes in symptomatology, indicatingthat the probabilistic reasoning bias is not a mediator ofdelusions in schizophrenia. However, the novel andintriguing finding that performance on the emotionallysalient version at baseline predicts subsequent change inpositive symptoms suggests that it may be a moderatorvariable in the presence of positive symptomatology.This finding also suggests that the JTC response patternmight be associated with positive symptoms rather thanspecifically to delusions. This may help explain whyother studies (Menon et al., 2006; Moritz and Wood-ward, 2005; Mortimer et al., 1996) failed to find asignificant difference between currently deluded andcurrently non-deluded schizophrenia patients, since thelatter group consisted of subjects who had delusions inthe past, and most of whom showed other positivesymptoms (i.e. hallucinations). One alternative hypoth-esis that we had considered was that treatment responsewas not predicted by performance on the probabilisticreasoning task, but merely that those people who did notshow the JTC response pattern were actually less symp-tomatic. However, the data suggests that the pattern ofresults remained unchanged both with and without usingbaseline PANSS scores as a covariate in the analysis.

The fact that performance on the emotionally salientversion of the probabilistic reasoning task acts as apredictor of the efficacy of antipsychotic medication onpositive symptoms might be an indicator of factorsunderlying delusion maintenance. Garety et al. (2005)found that absolute, dichotomous thinking (extremeresponding) and ‘jumping to conclusions’ thought toindicate a ‘data gathering bias’ were not related to oneanother, but were both related to belief in flexibility. It ispossible that the baseline JTC response pattern seen insome patients indicates inflexible beliefs, which in turn

prevents delusion resolution. However, it is somewhatsurprising that the change in response pattern was onlyseen on the emotionally salient version of the task, andnot on the neutral version. Dudley et al. (1997a) suggestthat the use of emotional material might heighten theJTC response pattern. It remains possible that it is thiscomponent of ‘emotional salience’ which is reduced inresponse to antipsychotic medication. However, giventhat both tasks are primarily probabilistic reasoningtasks, this does not appear to be an entirely satisfactoryexplanation. The lack of association with the neutralversion of the task might be an artifact of the smallsample size, or alternatively, indicate that performanceon some forms of probabilistic reasoning are relativelystable, and might indicate a vulnerability to the illnessitself, as has been suggested by others (Broome et al.,2004; Colbert and Peters, 2002; Van Dael et al., 2006).

We can conceptualize performance on the probabi-listic reasoning task as being a decision making task,where each incremental piece of information eitherbiases the system towards or away from a decisionthreshold. When conceptualized in this manner, the JTCresponse pattern might occur for two reasons — thedelusional state might be characterized by a lowereddecision threshold, or it might be that each piece ofinformation is over-weighted.

The first possibility, of a reduced decision thresholdwould result in a greater willingness to accept evenunfeasible or unlikely hypotheses, a ‘liberal acceptance’bias (Moritz et al., 2006). This assumption has somesupport from other studies using the JTC paradigm,which have shown that patients with delusions tend toshow not just a confirmatory bias, but also a greaterwillingness to change their decision when presentedwith disconfirmatory evidence (e.g. Garety et al., 1991),although some recent studies (Woodward et al., 2006)have argued against this.

The second possibility, that the decision threshold iscrossed with less information,might occur if each piece ofinformation appears more ‘salient’ than it actually is.Kapur (2003) and others (Berridge and Robinson, 1998)have suggested that dopamine might play a crucial role inmediating this ‘salience’, by converting ‘cold’ or neutralstimuli into ‘hot’ stimuli that are salient and occupy ourcognitive and attentional resources. Antipsychotics serveto act on the midbrain dopaminergic system. It could beargued that it is the pharmacologically mediated damp-ening of this salience, rather than changes in the cognitiveprocesses per se, that initially reduce delusional intensity.In the probabilistic reasoning task, this is reflected inreduced weighting given to each piece of information,resulting in an increase in the number of trials to decision.

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In subsequent phases, a change in the cognitive patterns,which can be produced by cognitive therapy would helpto prevent relapse or reduce the impact of the same delu-sional ideas in the future. In keeping with this, Lecomteet al. (2005) suggest that changes in JTC seen withpsychotherapy correlated with changes in delusions.

It remains possible that the association was seen bet-ween performance on the probabilistic reasoning task andpositive symptoms, rather than delusions specifically be-cause we had a relatively small sample, and the scores onthe positive symptommeasure showed awider distributionover the sample compared to the delusions score. Thestrength of the association (Spearman's rho values around0.6) suggests that the association is strong. Future studieswould be focused on seeingwhether task performance actsas an indicator of long term symptom relief or whether thisassociation is only associated with the early phases ofpharmacological therapy.

The study has a number of limitations. We used arelatively small sample of 19 first episode patients. As wewere examining the impact of medication on taskperformance, we did not include a healthy control group.This means that we cannot rule out the possibility that allparticipants would have taken more draws to decision onsubsequent testing session. However, we should stress thatthe novel finding is not that there are differences in thenumber of draws to decision over repeated testing sessions,but that baseline task performance is associated withtreatment response.

The use of the first episode subjects helps reducesome confounds of chronicity, cognitive decline andlong term medication use. However, the majority ofeven these patients had clear delusions at the time ofbaseline testing. Thus, while the study throws light onsome of the mechanisms involved with the maintenanceof delusions, it does not inform us about the factorswhich might be involved with the formation of de-lusions, which future studies, might address by lookingat prodromal populations.

Role of Funding SourceThis study was funded by a Canada Research Chair to Shitij Kapur.

The funding agency had no further role in study design; in thecollection, analysis and interpretation of data; in the writing of thereport; and in the decision to submit the paper for publication.

ContributorsMahesh Menon wrote the manuscript and carried out the statistical

analysis. RominaMizrahi wrote the study protocol and collected the data.Mahesh Menon and Romina Mizrahi carried out statistical analyses.Shitij Kapur and Romina Mizrahi designed the study. All authorscontributed to and approved the final manuscript.

Conflict of InterestAll authors declare that they have no conflicts of interest.

AcknowledgementsThe authors wish to thank David Mamo and Todd Woodward for

helpful discussions and Robert Zipursky for his useful comments on anearlier draft of the manuscript.

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