Correlates of hallucinations in schizophrenia:A cross‐cultural evaluation☆
P. Thomas a, P. Mathur a, I.I. Gottesman a,b, R. Nagpal c,V.L. Nimgaonkar a,d,e,⁎, S.N. Deshpande f,a
a Indo-US project “Genetic Susceptibility in Schizophrenia”, Department of Psychiatry, Dr. RML Hospital, Delhi, Indiab Department of Psychiatry, University of Minnesota Medical School, Minneapolis, MN
c Manobal Klinik, Rajouri Garden, New Delhi, Indiad Western Psychiatric Institute and Clinic, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
e Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA, USAf Department of Psychiatry, Dr. Ram Manohar Lohia Hospital, Delhi, India
Received 28 September 2006; received in revised form 24 January 2007; accepted 29 January 2007
☆ List of Contributors: P. Thomas— was responsible for data analysis and data management. P. Mathur — was responsible for data managementand analysis. I.I. Gottesman — undertook manuscript writing. R. Nagpal — was responsible for study design, data interpretation and manuscriptwriting. V.L. Nimgaonkar— was responsible for funding, design, analysis and manuscript writing. S.N. Deshpande— was responsible for funding,design, analysis and manuscript writing. All authors contributed to and have approved the final manuscript.⁎ Corresponding author. Western Psychiatric Institute and Clinic, Room 441, 3811 O'Hara St., Pittsburgh, PA 15213, USA. Tel.: +1 412 246 6353;
Please cite this article as: Thomas, P. et al., Correlates of hallucinations in schizophrenia: A cross‐cultural evaluation. Schizophr. Res. (2007),doi:10.1016/j.schres.2007.01.017
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1. Introduction
There was a resurgence of interest in hallucinationsfollowing a recent report of relatively high prevalence ofhallucinatory experiences (∼20%) even among unse-lected members of the Dutch population (van Os et al.,2001). The prevalence and characteristics of hallucina-tions were further evaluated during a survey of 265individuals, sampled from the population in Belgium(Laroi et al., 2004). Principal components analysissuggested four factors, including sleep related experi-ences, vivid daydreams, intrusive thoughts and ‘true’hallucinations. Thus, a sub‐group of unselected indivi-duals in the population may be experiencing psychoticexperiences similar to psychiatrically ill individuals.
Hallucinations form a core diagnostic feature ofschizophrenia (SZ). They can be debilitating andtherefore are important targets for therapy. There havebeen several systematic surveys of hallucinations instudies predating the era of structured diagnosticschedules (e.g. Bowman and Raymond, 1931). How-ever, there have been relatively few recent, systematicstudies on the prevalence of hallucination and associatedfactors in SZ or schizoaffective disorder (SZA),especially from non‐Caucasian samples. Recently,Baethge et al. (2005) estimated the cross‐sectionalprevalence of hallucinations among inpatients withschizophrenia at 61.1%. A systematic study of halluci-nations among US patients with schizophrenia wasreported in 1990 (Mueser et al., 1990). Mueser andcolleagues documented different types of hallucinationsamong 117 patients at a hospital in Philadelphia. Theyreported that auditory hallucinations are the mostcommon, followed by visual, tactile, olfactory andgustatory hallucinations. The presence of olfactory andgustatory or tactile hallucinations was correlated in thisstudy. However, the prevalence of these types ofhallucinations varies widely in different series: auditoryhallucinations were present among 47% to 98% ofpatients (Mueser et al., 1990; Zarroug, 1975; Bracha etal., 1989; Suhail and Cochrane, 2002; Goldberg et al.,1965), visual hallucinations from 14 to 69% (Mueser etal., 1990; Zarroug, 1975; Bracha et al., 1989; Suhail andCochrane, 2002) and tactile hallucinations from 4 to25% of patients (Mueser et al., 1990; Bracha et al.,1989). The wide variation suggests heterogeneity inschizophrenia, despite the use of structured diagnosticcriteria. Therefore, it is of interest to examine factors thatimpact on the heterogeneity.
Some studies have suggested correlations betweenhallucinations and clinical indices of severity. Forexample, Mueser et al. (1990) reported that olfactory
Please cite this article as: Thomas, P. et al., Correlates of hallucinations indoi:10.1016/j.schres.2007.01.017
and gustatory or tactile hallucinations were the harbin-gers of severe delusions. The authors also noted thatauditory hallucinations were correlated positively withan earlier age at hospitalization among patients withschizophrenia. The overall severity of illness was alsorelated to the presence of visual hallucinations amongpatients with schizophrenia. On the other hand, nosignificant difference in the prevalent rates of differenttypes of hallucinations were noted among patients withschizophrenia or schizoaffective disorders, two disor-ders with differing outcomes. Another study that set outto evaluate the relationship between severity andprevalence of hallucinations also did not find correla-tions with age at onset (a proxy for severity) (Sharma etal., 1999). Interestingly, this study reported that femalegender predicted a higher frequency of hallucinations.Since women with schizophrenia tend to have a morebenign course of schizophrenia than men, the relation-ship between severity and hallucinations remainsunresolved.
The significant correlation of visual hallucinationswith severity of illness is of interest because someresearchers have suggested that visual hallucinations areunder‐reported among US samples, possibly becausepsychiatrists do not inquire systematically about suchhallucinations (Bracha et al., 1989). These results arealso of interest because visual hallucinations arereported to be relatively more common in non‐westernpopulations. A report from Saudi Arabia suggested that62% of patients had visual hallucinations (Zarroug,1975). It was suggested that cultural factors couldexplain the relatively high rates. This possibility wasexplored systematically in a study of individuals ofPakistani origin residing in the UK, who were comparedwith Pakistani patients in Pakistan, as well as Britishwhite patients (Suhail and Cochrane, 2002). There wasgreater difference in the phenomenology of delusionsand hallucinations between the Pakistani individualsresiding in the UK versus those in Pakistan, thanbetween the UK Pakistani and the British white groups.It was thus suggested that the immediate environmentmay have a strong impact on the content of delusionsand hallucinations. These intriguing results were basedon a case note survey supplemented with interviewswith clinicians as needed. It would be important toevaluate them systematically using semi‐structuredinterviews, with due sensitivity to the cultural settings(Jablensky et al., 1994).
Studies of hallucinations and their precursors in thecausal chain between genotypes and clinical diagnosesof schizophrenia may also be relevant in view of thepresent interest in evaluating psychopathology beyond
schizophrenia: A cross‐cultural evaluation. Schizophr. Res. (2007),
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the conventional diagnostic boundaries. In particular,there is an active effort to evaluate endophenotypes, i.e.,traits that are heritable and may occur proximal to thediagnostic phenotype in the chain of pathogenesis(Gottesman and Gould, 2003; Bearden and Freimer,2006). Mapping genes contributing to such traits wouldpresumably facilitate efforts to identify genes fordisorders in which these traits can be observed. Fromthis vantage, hallucinations themselves are not plausibleendophenotypes per se, as they are readily observedwithout special instruments. If, for example, exposure tolow doses of cannabis elicited mild hallucinations in theclinically normal relatives of schizophrenics, but not inmatched controls, we would be on the trail of anendophenotype revealed by a challenge to brainfunctioning (Gould and Gottesman, 2006). Indeed,factor analyses of twins with psychoses spanning theschizophrenia – schizoaffective – bipolar disorderspectrum suggest patterns of familial aggregation forseveral factors, including hallucinations (Cardno et al.,2001). Model fitting further suggested shared geneticfactors for all three diagnostic entities (Cardno et al.,2002).
Shared heritability for hallucinations can also beinvestigated indirectly through pairs of affected relativesother than twins. Statistically significant similaritywould suggest a role for shared genetic and/orenvironmental factors. Using this approach, DeLisiand colleagues reported that auditory hallucinationswere not associated among siblings (DeLisi et al., 1987).Another study of systematically ascertained families inIreland also failed to detect significant correlationsbetween pairs of affected sibling pairs (ASPs), suggest-ing that familial factors may not have a significant rolein the onset of hallucinations (Kendler et al., 1997).Similarly, a study of Chinese ASPs (n=46 pairs) alsodid not detect significant correlations with the presenceof hallucinations (Hwu et al., 1997).
The present study was undertaken to estimate thetypes and prevalence of hallucinations among system-atically evaluated groups of patients. First, we estimatedthe prevalence of different types of hallucinations usinglifetime figures. Second, associations between thehallucination and relevant demographic and clinicalfactors were investigated, with emphasis on indices ofseverity. Third, we assessed the familial concordance forhallucination, among affected sibling pairs (ASPs).These analyses were conducted among two indepen-dently treated samples recruited from India and USusing identical procedures. We reasoned that thesimultaneous analyses would enable us to understandcorrelates of hallucinations in two very different
Please cite this article as: Thomas, P. et al., Correlates of hallucinations indoi:10.1016/j.schres.2007.01.017
environmental settings. Any common features observedduring the analyses would be robust. Since the US andIndian samples could not be considered to be repre-sentative of their countries, direct comparisons betweenthe samples were not conducted.
2. Methods
Patients were recruited as part of an ongoing study inthe genetics of schizophrenia, being conducted by USand Indian investigators in parallel using identicaldesigns (Deshpande et al., 2004). Affected individualswith either affected sibling/s or both parents willing toparticipate and with a consensus diagnosis of SZ/ SZAdisorder (DSM IV) are recruited and evaluated follow-ing written informed consent. Ethical approval has beenobtained from Institutional Review Boards (IRB) at Dr.Ram Manohar Lohia Hospital and the University ofPittsburgh for the US.
Interviews were conducted using the English orHindi version of the Diagnostic Interview for GeneticStudies (DIGS), (Deshpande et al., 1998; Nurnberger etal., 1994). Available medical records were examinedand additional clinical details were obtained fromrelatives as required. The clinical variables includedfor analysis were auditory hallucinations (voice, threat),somatic or tactile, olfactory, visual and gustatoryhallucinations (all, “ever present”), gender, age atonset, years of schooling, marital status, pattern ofsymptoms, severity of illness and diagnosis.
The first ascertained case in each family wasconsidered the proband. For all the analyses, only onepatient was included from each family except for theaffected sib‐pair analyses. There were 117 multiplyaffected families from India and 71 such families fromthe US. Two or more affected siblings participated fromeach of these families. Among families in which morethan one affected sib participated (India: n=17, US:n=4), the same proband was evaluated sequentially inconjunction with all the other affected siblings. Thus,two ASPs would be counted from a family with threeaffected siblings and three ASPs for a family with fouraffected siblings. Therefore, 117 multiply affectedfamilies from India and 71 multiply affected US familiescontributed 136 ASPs and 77 ASPs, respectively.
3. Statistical analysis
Analysis carried out for the study included descrip-tive statistics, chi‐square test, Pearson's correlation,measures of agreement and logistic regressions. TheStatistical Package for Social Sciences version 11.5
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(SPSS 11.5) was used for the analysis and level ofstatistical significance fixed at p=0.05.
4. Results
There were 807 participants from India, and 480from the US. Data for “singleton” cases (i.e., patientswho did not report having affected siblings, togetherwith one proband from each affected sibling pair family)were analyzed initially, followed by analyses of affectedsibling pairs (ASPs). For each set of analyses, theprevalence of different variables was estimated sepa-rately for the Indian and US samples, followed byanalyses with regard to hallucinations.
4.1. Analyses of singleton cases
4.1.1. Demographic and clinical featuresThe demographic and clinical features for both
samples are presented in Table 1. The samples couldnot be considered representative of their nationalities,hence formal statistical comparisons were not madebetween the US and Indian samples. Nevertheless, therewere remarkable demographic and clinical differences.The Indian sample was younger than the US sample,overall. The genders were represented more evenly inthe Indian samples, while there was an excess of menamong the US patients. The US patients appeared tohave longer periods of education than the Indianpatients, but were more likely to be unmarried.Individuals with schizophrenia were over representedin the Indian samples, whereas the distribution of thesetwo disorders was more equitable in the US sample. Theages at onset were similar, but the Indian sampleappeared more severely impaired in comparison with
Table 1Demographic and clinical characteristics of singleton cases
India (n=807)
Age 30.8±9.8Gender (male/female) 437/370 (54.2%/45.8%)Education (0–5/6–12/>12 years) 62/435/310 (7.7%/53.9%Marital status (ever married/never married) 344/463 (42.6%/57.4%)Diagnosis(schizophrenia/schizoaffective disorder)
706/101 (87.5%/12.5%)
Age at onset 22.8±7.2Global assessment of function 22.0±9.4Pattern of symptoms⁎ 362/19/50/4/371 (44.9%
Pattern of severity⁎⁎ 57/201/310/229/7 (7.1%
⁎Pattern of symptoms: continuously positive/predominantly negative/positipositive and negative symptoms. ⁎⁎Pattern of severity: episodic shift/mild deSome data were missing for the US sample.
Please cite this article as: Thomas, P. et al., Correlates of hallucinations indoi:10.1016/j.schres.2007.01.017
the US sample. The patterns of symptoms and severityalso were different. Indian patients were more likely tohave a pattern of ‘negative’ symptoms changing to‘positive’ symptoms longitudinally. There appeared tobe an over‐representation of US cases with moderateto severe deterioration.
There were 601 patients (74.7%) from India and 423(88.5%) from the US who reported lifetime occurrenceof hallucinations (Table 2). Auditory voice hallucina-tions were the most common in both samples, followedin order of frequency by visual, somatic/tactile,olfactory and gustatory hallucinations. This order waspresent in the US, as well as the Indian samples.
4.1.2. Associations of relevant demographic andclinical variables with hallucinations
To evaluate clinical and demographic featuresassociated with different types of hallucinations, a seriesof logistic regression analyses were conducted sepa-rately for the US and the Indian samples. In each set ofanalysis, the outcome was the type of hallucination(auditory, visual, somatic/tactile, olfactory and gusta-tory). The covariates were age, gender, level ofeducation, age at onset, diagnosis, GAF score, patternof symptoms and pattern of severity. In these analyses,GAF scores and educational status were classified as
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categorical variables. GAF scores were considered indeciles (scores 0–10, 11–20 etc) and educational statuswas considered in three groups (0–5 years, 6–12 yearsand above 12 years of education). The followingassociations were detected from the logistic regressionanalyses (details in Table 3).
4.1.3. Auditory hallucinationsIn the Indian sample, the only significant correlation
was noted with the pattern of symptoms. Inspection ofthe data suggested that the significant effect was due tothe increased prevalence of hallucinations in the groupwith ‘continuously positive’ symptoms (Odds ratio, OR1.6) versus patients with a mixture of positive andnegative symptoms. In the US sample, significantcorrelation with diagnosis was noted. With schizoaffec-tive disorder as reference, the OR among patients withschizophrenia was 2.3.
4.1.4. Visual hallucinationsSeveral significant correlations were noted in the
Indian samples, including patterns of symptoms (OR 1.6
Table 3Logistic regression analyses
India
p OR 95% CI
Auditory hallucinationsPattern of symptoms: continuously positive 0.004 1.60 1.17–2.1
Visual hallucinationsGender: female 0.049 1.35 1.00–1.8Pattern of symptoms: continuously positive 0.004 1.60 1.15–2.2Pattern of severity
Marital status: ever married 0.050 1.45 1.00–2.0Educational status
0–5 years of education 0.001 2.76 1.53–4.96–12 years of education 0.025 1.46 1.05–2.0
Age 0.043
Somatic hallucinationsPattern of symptoms: continuously positive 0.018 1.53 1.08–2.1
Olfactory hallucinationsPattern of symptoms: continuously positive 0.020 1.55 1.07–2.2
Gustatory hallucinationsMarital status: ever married 0.029 1.94 1.07–3.5
Reference classes=for pattern of symptom: mixture of positive and negativstatus: never married; for education status: above 12 years of education; for
Please cite this article as: Thomas, P. et al., Correlates of hallucinations indoi:10.1016/j.schres.2007.01.017
for patients with ‘continuously positive’ pattern ofsymptoms versus patients with mixture of positive andnegative symptoms), pattern of severity (in comparisonwith patients showing ‘episodic shift’, patients withmoderate or severe deterioration were more likely toreport visual hallucinations, OR 2.4 and 3.0, respec-tively); marital status (‘ever married’ patterns had agreater risk for hallucinations compared with ‘nevermarried’ patients, OR 1.5), educational status (withreference to individuals with more than 12 years ofeducation, individuals with 0–5 years of education had agreater likelihood of visual hallucinations, OR=2.8, andthose with 6 to 12 years of education had an OR of 1.5),sex (‘female’ gender had slightly higher risk for visualhallucination compared with ‘male’ gender) and age(younger patients were more likely to report hallucina-tions, beta coefficient=−0.02, p=0.043). Among theUS cases, correlations with the following variableswere noted: diagnosis (patients with SZ had 1.7 greaterodds of having visual hallucinations compared withpatients diagnosed with SZA), age at onset (inversecorrelation, beta coefficient=−0.03, p=0.025) and
USA
p OR 95% CI
9 Diagnosis: schizophrenia 0.004 2.27 1.31–3.94
2 Diagnosis: schizophrenia 0.016 1.74 1.11–2.733 Age at onset 0.038
Pattern of symptoms3 Continuously positive 0.002 0.40 0.22–0.7227
75
8 Marital status: ever married 0.008 2.05 1.21– 3.49Pattern of severitySeverely deteriorate 0.046 3.74 1.02–13.67Relatively stable 0.015 8.34 1.51–45.96
4
1
e; for gender: male; for pattern of severity: episodic shift; for maritaldiagnosis: schizoaffective.
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pattern of symptoms (OR=0.4. Patients with continu-ously positive symptoms had 0.4 times less riskcompared to patients with mixture of positive andnegative symptoms). Thus, pattern of symptoms was acommon correlate of visual hallucinations in bothsamples, but had contrasting results in the Indian andUS samples.
4.1.5. Somatic hallucinationsIn the Indian sample, the term ‘pattern of symptoms’
was correlated with presence of somatic hallucinations(patients with continuously positive symptoms had 1.5times greater risk in comparison with patients having amixture of positive and negative symptoms). In the USsample, the significant correlates were: marital status(those who had been married had 2.1 fold greater riskcompared with never married individuals) and pattern ofseverity (patients with ‘severe deterioration’ had 3.7times of risk for somatic hallucination and patients withrelatively stable pattern of illness had 8.3 times of riskfor hallucinations compared with those having episodicshifts, however the former category (“relatively stable”)included only 19 patients).
Table 4Demographic and clinical features of affected sibling pairs
India (n=136 pairs)
Proband Sibling C
Age 35.3±10.4 34.9±10.4 r=p=
Gender(male/female)
71/65(52.2%/47.8%)
80/56(58.8%/41.2%)
χ2
p=Education(0–5/6–12/>12 years)
8/75/53(5.9%/55.1%/39%)
10/81/45(7.4%/59.6%/33.1%)
χ2
p=
Marital status(ever married/never married)
74/62(54.4%/45.6%)
67/69(49.3%/50.7%)
χ2
p=
Diagnosis(schizophrenia/schizoaffectivedisorder)
123/13(90.4%/9.6%)
121/15(89%/11%)
χ2
p=
Age at onset 23.4±6.5 24.2±7.3 r=p=
Global assessmentof function⁎
23.13±9.4 23.10±9.7 r=p=
Pattern ofsymptoms⁎⁎
1/2/3/4/5
68/2/0/14/52(50%/1.5/0/10.3/38.2)
66/10/11/0/49(48.5%/7.4/0/8.1/36.0)
χ2
p=
Pattern ofseverity⁎⁎⁎
1/2/3/4/5
15/32/53/33/3(11%/23.5/39/24.3/2.2)
26/31/52/25/2(19.1%/22.8/38.2/18.4/1.5)
χ2
p=
⁎Sample size for GAF–India–Proband: Sib=116: 85 and US–Proband: Sib=to negative, 4–negative to positive, 5–mixture of positive and negative. ⁎⁎
severe deterioration, 5–relatively stable.
Please cite this article as: Thomas, P. et al., Correlates of hallucinations indoi:10.1016/j.schres.2007.01.017
4.1.6. Olfactory hallucinationsIn the Indian sample, patterns of symptoms were
correlated with the presence of olfactory hallucinations(patients with continuously positive symptoms had a 1.6times greater probability of hallucinations comparedwith patients having a mixture of positive and negativesymptoms). No significant correlates were detected inthe US sample.
4.1.7. Gustatory hallucinationsThe only significant correlation was with marital
status in the Indian sample (ever married patients had1.9 times greater risk than never married patients).
4.2. Analysis of ASPs
The sample included 17 families in the Indian sampleand 4 US families in which more than two siblings wereaffected. To maximize information, all sibs werecompared with the proband in each family. There werethus 136 ASPs from India and 77 ASPs from the US.The demographic and clinical features of the ASPs arepresented in Table 4. Their ages, educational status,
Correlations are reported as kappa values, with significance (p‐values)in brackets.
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marital status, diagnoses, GAF scores and ages at onsetwere significantly correlated in both the samples. On theother hand, the pattern of symptoms and pattern ofseverity were correlated among the US, but not theIndian ASPs. The gender distribution was not signifi-cantly correlated in either sample.
We next evaluated correlations for hallucinationsamong the ASPs. Significant correlations for auditoryhallucinations were detected among the US ASPs, butnot among the Indian ASPs. The former correlation mayhave been inflated by the relatively high prevalence ofauditory hallucination in the US sample (83.4%, seeTable 2). Significant correlations with visual hallucina-tions were not observed in the US or the Indian ASPgroups, but significant correlations were detected forgustatory hallucinations among the Indian ASPs(kappa=0.180). Among the US ASPs, significantcorrelations were noted for somatic hallucinations.With regard to olfactory hallucinations, correlationswere observed in opposite directions (kappa=−0.078,and −0.250, in the Indian and US samples, respectivelyand also it was significant in US sample; see Table 5).The correlations for gustatory and somatic hallucina-tions could not be evaluated meaningfully becausethey were relatively infrequent. For example, onlythree ASPs were concordant in the Indian sample. Inthe same vein, only six US patients had somatichallucinations.
5. Discussion
The present analyses were undertaken in order toevaluate factors associated with different types ofhallucinations. Our goal was to identify correlationsthat might have clinical relevance. The presence andseverity of hallucinations is critically dependent on themedications administered to patients. Since the cross‐sectional nature of our studies precluded carefulestimation of the impact of medications, we sought tocircumvent this shortcoming by evaluating the lifetimeoccurrence of hallucinations.
Please cite this article as: Thomas, P. et al., Correlates of hallucinations indoi:10.1016/j.schres.2007.01.017
We conducted our analyses simultaneously in twoindependent samples that were evaluated using identicalprocedures. We assumed that similar correlations fromanalyses of samples ascertained in very different settingswould be more likely to be replicable in other settings, incomparison with results from solitary samples. Ouranalyses did not reveal any remarkable consistencybetween the Indian and the US samples. These analysessuggest that the factor structure of the differentmodalities of hallucinations vary by site.
Auditory hallucinations have been noted in allcultures investigated to date (WHO) (Sartorius et al.,1972; Jablensky, 1995; Jablensky et al., 1994). Theprevalence of auditory hallucinations differed in thesamples (64.3% in India versus 83.4% in the USsample). The prevalence of visual hallucinations washigher in the US sample (Indian sample: 36.9%, USsample: 57.2%), as also the prevalence of gustatoryhallucinations. On the other hand, the prevalence ofsomatic and olfactory hallucinations was similar in thesetwo samples. We did not compare the rates formally, nordid we compare other variables because these samplescannot be considered representative of their nations.While the prevalence of auditory hallucinations in thepresent report was similar to previous studies, our studyrevealed higher prevalence for visual and somatichallucinations. The higher rates may reflect that theseabnormalities were sought painstakingly during thecourse of semi‐structured interviews, complemented bymethodical hospital note reviews.
A key aspect of our analyses was the putativerelationship between severity of illness and the presenceof particular types of hallucinations. Previous studieshave suggested a positive correlation between presenceof visual hallucinations and severity of illness (Mueser etal., 1990). Since illness severity is multi‐dimensional, weselected a number of different variables. These variablesincluded the GAF score during the most severe phase ofthe illness, as well as an overall rating of pattern ofseverity of illness available in the GAF. Finally, we alsoused age at onset, since this variable is correlated withillness severity, but unlike most other measures ofseverity, is unaffected by medications. Age at onset wasinversely correlated with visual hallucinations in theIndian sample, consistent with Mueser's observations,though the magnitude of the correlation was relativelysmall. On the other hand, a similar correlation was notobserved in the US sample. However, the term ‘pattern ofseverity’ was correlated positively with the presence ofvisual hallucinations in the Indian sample, consistentwith Mueser's results. Paradoxically, somatic hallucina-tions were associated with relatively stable patterns in the
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Indian sample. The relatively small number of indivi-duals in this category precludes firm conclusions.Interestingly, GAF scores were not significantly asso-ciated with the presence of hallucinations in any of theanalyses, suggesting that there is no straightforwardrelationship between the presence of hallucinations andillness severity.
A number of other interesting correlations wereobserved. The presence of auditory and visual halluci-nations was more likely among US patients with adiagnosis of schizophrenia in contrast to those withschizoaffective disorder. Such an association was notobserved among the Indian patients, possibly becausethere were relatively few patients with schizoaffectivedisorder in this group. Our results are in contradiction toan earlier report in which a diagnosis of schizoaffectivedisorder was associated with greater risk for visual orsomatic hallucinations (Mueser et al., 1990).
Marital status was also associated with hallucina-tions in three sets of analyses. Among the Indianpatients, individuals who had been married were morelikely to manifest visual or gustatory hallucinations,compared with individuals who had never beenmarried. There is no obvious explanation for theseobservations, which could be considered chance resultsbut for the fact that the same relationship was alsoobserved among US patients with respect to olfactoryhallucinations. In the Indian sample, the presence ofauditory, visual, somatic or olfactory hallucinations wasincreased among patients classified as having con-tinuously positive symptoms in comparison withpatients thought to have combinations of positive andnegative symptoms. In contrast, among the US patients,visual hallucinations were more likely to be observedamong the latter group of patients when contrasted withthose classified as having ‘continuously positive’symptoms. These differences suggest that the correla-tion with patterns of symptoms may not be observedconsistently across cultures. A few other marginallysignificant correlations between the presence of visualhallucinations on one hand and age, gender andeducational status were observed, but only in theIndian sample.
We also analyzed concordance of different modalitiesof hallucinations among pairs of affected siblings, sincestatistically significant correlations would suggestshared genetic/environmental factors in the genesis ofhallucinations. In contrast to the singleton samples, thenumber of ASPs available for analysis was muchsmaller. In order to maximize the chances of observingcorrelations, we analyzed all combinations of ASPs withthe proband when more than two affected siblings were
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present in a family. The Indian and the US ASPs wereconcordant for a number of clinical and demographicvariables. Nevertheless, no striking correlations wereobserved with regard to the lifetime occurrence ofhallucinations, barring a marginally significant concor-dance for gustatory hallucinations among the IndianASPs. These analyses suggest a significant impact ofnon‐shared environmental factors in the genesis ofhallucinations. On the other hand, twin and family datasuggest a multi‐factorial/polygenic fits best for diag-noses of schizophrenia, overall, with heritable compo-nents predominating. (Gottesman, 1991). While analysisof individual psychopathological features has beenconducted less frequently, such analyses also point to acomplex etiological model (Gottesman and Shields,1972; Cardno and Gottesman, 2000).
Several previous studies reported on prevalence andtypes of hallucinations but inconsistencies were present.Variations in sample size could be one explanation forthe inconsistencies. We sought to address some of thesevariables by analyzing moderately large samples thatwere assessed similarly. Despite this design, we did notobserve any consistent correlations that could beconsidered useful in the clinical setting. Our analysessuggest that the factors associated with hallucinationsvary across different environments. There are no clearcut associations between illness severity and particularforms of hallucinations, nor did we observe anysignificant concordance among ASPs.
Acknowledgements
The authors thank Dr. T. Bhatia for helpfulcomments.
Funding for this study was provided by NIH Grants:MH01489, MH56242 and MH53459, R03 TW00730,and Indo‐US Project Agreement no. N‐443‐645). TheNIH had no further role in study design; in the col-lection, analysis and interpretation of data; in the writingof the report; and in the decision to submit the paper forpublication.
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