Minnesota Multiphasic Personality Inventory profile characteristics of schizotypal personality disorder

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  • Psychiatry and Clinical Neurosciences (2002), 56, 443452

    Regular Article

    Minnesota Multiphasic Personality Inventory profilecharacteristics of schizotypal personality disorder

    MI MATSUI, phd,1 TOMIKI SUMIYOSHI, md,2 LISHA NIU, md,1

    KENZO KUROKAWA, md2 AND MASAYOSHI KURACHI, md2Departments of 1Psychology and 2Neuropsychiatry, School of Medicine,Toyama Medical and PharmaceuticalUniversity,Toyama, Japan

    Abstract The goal of the present study was to determine whether precursors for psychopathology can befound in personality dimensions of the general population. Two hundred and 62 university stu-dents were compared with 41 schizophrenic patients and 18 patients with schizotypal personalitydisorder (SPD) on the Minnesota Multiphasic Personality Inventory (MMPI). Schizotypal personality disorder patients showed significantly elevated Pt and Si scales compared with theschizophrenic patients. Schizophrenia and SPD groups generally produced two-point codetypesof 68/86, 26/62, 78/87, and 78/87, 27/72, 68/86. A total of 77.5% of students had nocodetype with a T-value of 70, although the frequency of codetypes of spike 5, spike 0 and27/72 was relatively high in the student group compared with the general population. Discrimi-nant function analysis of the MMPI profiles revealed significant variance among the threegroups. The overall rate of correct classification of the subjects into schizophrenia, SPD or uni-versity students was 90.3%. The first coefficient, mainly defined by a negative weight on the Scscale, best distinguished the patients with either schizophrenia or SPD from the students. Thesecond coefficient, defined by negative weights on the Sc and Si scales, and positive weights onthe F and Ma scales identified patients with schizophrenia and SPD patients. The Harris-Lingoessubscales, which are supposed to provide the profile patterns characteristic of schizotypy, welldiscriminated the three groups. These results suggest the usefulness of the MMPI subscales forthe detection of subjects with the SPD trait.

    Key words Harris-Lingoes scales, mental health, Minnesota Multiphasic Personality Inventory, psy-chopathology, schizophrenia, schizotypal personality disorder, university students.

    INTRODUCTION

    The Minnesota Multiphasic Personality Inventory(MMPI) is one of the widely used objective tests ofpersonality and has the ability to detect both schizo-phrenia and schizophrenia-related conditions to somedegree. It also provides transmissible indicators forthe liability to develop schizophrenia.1,2 Several previ-ous studies have attempted to determine in healthypeople whether precursors for psychopathology can

    be found in personality dimensions, which are measured by the MMPI. Thus, Claridge and Beechdescribed the dimensional personality-based con-tinuity models of schizotypy and schizophrenia.3 Thismodel predicts that the trends toward psychopatho-logical personality in healthy people predisposes topsychopathology (i.e. the biological liability for schizophrenia may be expressed as schizotypal per-sonality organization).3 Some studies have attemptedto clarify in healthy people the association betweenpersonality traits as assessed by the MMPI and bio-logical markers.47 Recently, Matsui et al. have pro-vided evidence that in healthy people the high Scscale of the MMPI was associated with reducedfrontal white matter volume as measured by magneticresonance imaging (MRI).4 These findings suggestthat personality dimensions may be linked to someneural substrates.

    Correspondence address: Mi Matsui, Department of Psychology,School of Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan. Email:mmatsui@ms.toyama-mpu.ac.jp

    Received 29 August 2001; revised 28 November 2001; accepted 2December 2001.

  • 444 M. Matsui et al.

    Other investigators have administered several kindsof psychological tests, in addition to the MMPI, touniversity students in order to identify individualswho have schizotypal personality, and compared theMMPI profiles between subjects who were consideredto have schizotypal personality and those who werenot.810 Thus, Haier et al. compared results from theMMPI and those from the Research Diagnostic Criteria (RDC) in college students, and found acertain degree of correlation between specific MMPIcodetypes and the RDC evaluations.8 Similarly,Moldin et al. identified the schizophrenia-relatedcodetypes of the MMPI.11 Lenzenweger9 used thePerceptual Aberration Scale (PAS)12 as a measure ofschizotypal personality, and found that the PAS-iden-tified schizotypic students showed schizophrenia-related MMPI high-point codes more frequently thanthe controls. On the other hand, Merritt et al.10 foundno evidence for correlations between the diagnosis ofschizotypy based on the Social Anhedonia Scale(SAS)13 and the MMPI profiles.

    The primary purpose of the present study was to compare the MMPI profiles, including theschizophrenia-related high-point codetypes11 in addi-tion to the individual subscales, among patients witheither schizophrenia or schizotypal personality disor-der (SPD) and university students. In addition, as thecodetypes of MMPI typically have been determinedaccording to the high-point pairs (i.e. the two highestscales with T scores of more than 70),14 we examinedall two-point codetypes and compared them betweenpatients with schizophrenia and those with SPD. Thesecond purpose was to determine the ability of theMMPI to distinguish among subjects with schizophre-nia or SPD, and normal students, using multiple dis-criminant function analyses. In view of the continuitymodels of healthy people and patients with schizo-phrenia-spectrum disorders, it is hypothesized that acertain degree of overlap between university studentsand patients with schizophrenia or SPD exists interms of the MMPI profiles. Therefore, we sought toidentify a measure of the liability to schizotypy byanalyzing the MMPI profiles. Our a priori hypothesiswas that subjects with SPD are associated with moredistress, irrational struggle, social withdrawal and soon, which are represented by the correspondingMMPI subscales and profiles, compared with patientswith schizophrenia or normal students.

    METHODS

    Subjects

    The sample included 326 participants (59 patients and267 students). A total of 267 freshmen (115 males and

    152 females) who entered Toyama Medical and Pharmaceutical University, Toyama, Japan, in 1998participated in the study. The mean age of these subjects at the time of testing was 19.2 (SD 2.1) years.

    The clinical group consists of 41 patients with schizophrenia (23 males and 18 females) and 18patients with schizotypal disorder (17 males and onefemale) who meet the ICD-10 Diagnostic Criteria forResearch.15 Schizotypal disorder is characterized byeccentric behavior and anomalies of thinking andaffect which resemble those seen in schizophrenia,although no definite and characteristic schizophrenicanomalies have occurred. The clinical picture ofschizotypal disorder is similar to the prodromal stateof schizophrenia. The phenomenological differencesbetween schizotypal disorder and schizophrenia arethe absence of overt symptoms and the presence ofsustained psychotic symptoms. Eighteen patients withschizotypal disorder have never met criteria for schizophrenia itself. The mean age of schizophreniaand SPD subjects was 29.2 (SD 7.0) and 24.0 (SD 8.0)years, respectively. All patients were under 45 years ofage. The mean duration of illness for the schizophre-nia and SPD subjects was 4.6 (SD 5.1, range 0.0821)and 2.2 (SD 2.9, range 0.0211) years, respectively. Themean daily haloperidol-equivalent neuroleptic dosesfor schizophrenia and SPD subjects were 8.6 (SD 8.9,range 0.637.8) and 4.4 (SD 8.2, range 032.9) mg,respectively. Diagnoses were made by experiencedpsychiatrists using medical histories. All patients werephysically healthy at the time of the study, and nopatient had a history of head trauma, serious medicalor surgical illness, or substance abuse.

    Personality assessment

    All subjects gave informed consent before enteringthe study. The new Japanese version of MinnesotaMultiphasic Personality Inventory (MMPI) wasadministered to students as a routine mental healthcheckup during the orientation following entranceinto the university. All patients were administered thefull version of the MMPI by well-trained clinical psychologists in a quiet, comfortable, conventionallylit testing room. The MMPI is a widely used instru-ment for personality assessment with established psy-chometric properties. The new Japanese version of theMMPI was recently revised following comprehensivere-standardization in 1993.16 To date, there have beenseveral Japanese versions of the MMPI which havebeen used since the 1950s. However, they wereviewed as decreasingly applicable in contemporarysociety, as the original Japanese MMPI items andnorms were translated and developed about 40

  • 50 years ago. The last Japanese version had someproblems: one problem is that of mistranslation;second, there was sample bias of population for nor-malization (i.e. 80% of subjects was less than 30 yearsold); third, basic materials of normalization such aspercentage of endorsement and distribution of two-point codes have not been published. The new Japan-ese version was based on the MMPI, but not MMPI-2,as there has been vast information on the MMPI. Thenew version was developed based on considerationsof nine previous Japanese versions. Sampling for nor-malization was based on a national census. Thus, thevalidity and reliability of the new version of MMPIhave been confirmed17 and it is at present in commonuse in Japan.

    Initially, we analyzed the 13 basic scores consistingof three validity and 10 clinical scores. The threevalidity scales (L, lie; F, infrequency; K, defensiveness)provide information about the sub