PSYCHIATRIC SERVICES July 2000 Vol. 51 No. 7922

Characteristics of SchizophreniaAmong Persons With Severe orProfound Mental RetardationKatie E. Cherry, Ph.D.David Penn, Ph.D.Johnny L. Matson, Ph.D.Jay W. Bamburg, M.S.

The symptoms of schizophreniawere examined in a residentialsample of adults with severe orprofound mental retardation.Three groups were compared:those with a significant elevationon the schizophrenia subscale ofthe Diagnostic Assessment for theSeverely Handicapped (DASH-II)and a psychiatric diagnosis ofschizophrenia; those with a signif-icant elevation on the same sub-scale but no formal diagnosis ofschizophrenia; and those with noelevation on any of the DASH-IIsubscales. A one-way analysis ofvariance showed statistically sig-nificant differences between thegroups. Symptoms of schizophre-nia among those in the first groupwere found to fall mainly into thecategories of reality distortionand disorganization, with less evi-dence of negative symptoms.(Psychiatric Services 51:922924,2000)

Adults with mental retardation ex-hibit the same types of psychi-atric disorders as adults of normal in-telligence, although an accurate diag-nosis is often difficult to make. Diag-nostic overshadowing, for example, in

which abnormal behaviors are as-sumed to be the result of mental re-tardation rather than potential co-morbid psychopathology, may ob-scure identification of psychiatricconditions. An examination of specif-ic types of disorders is needed for amore complete understanding of theclinical features of psychiatric disor-ders in persons of varying levels of in-tellectual impairment (1).

In this study we focused on the co-occurrence of schizophrenia in per-sons with severe or profound mentalretardation. Historically, dual diagno-sis of schizophrenia and mental retar-dation has been a source of contro-versy (2). Deficits in language abilitymay hamper or preclude self-reportsof delusions, hallucinations, and otherexpressions of disordered thoughtthat are the hallmark diagnostic crite-ria for schizophrenia. Nonetheless,persons with mental retardation showthe full range of psychiatric disorders,including schizophrenia (3).

Our primary aim in this study wasto provide a broad description of thesymptoms of schizophrenia in a resi-dential sample of adults with severeor profound mental retardation. Wecompared the lists of symptoms thatled to psychiatric diagnoses of schizo-phrenia in this sample with the symp-toms of schizophrenia that are char-acteristic of persons of normal intelli-gence, following the Lenzenwegerand Dworkin four-factor structure ofschizophrenia phenomenology (4).Evidence showing similarity of symp-toms may help in identifying common

behavioral or physical signs of schizo-phrenia and may lead to the develop-ment of empirically based criteria forthe diagnosis of schizophrenia in per-sons with severe or profound mentalretardation.

MethodsParticipants were 60 residents of alarge developmental center in centralLouisiana. All were classified as hav-ing severe or profound mental retar-dation (82 percent and 18 percent,respectively).

Twenty of the participants had a di-agnosis of schizophrenia that was ob-tained through the following proto-col. A licensed psychologist was giveninformation from the Diagnostic As-sessment for the Severely Handi-capped (DASH-II) (5), other behav-ioral rating scales, social skills mea-sures, and behavioral observations.After reviewing this information andthe DSM-IV criteria for schizophre-nia, the psychologist decided whetherthe diagnosis of schizophrenia waswarranted. A board-certified psychia-trist reviewed the information forthose who met DSM-IV criteria forschizophrenia. If the psychiatrist andthe psychologist considered the infor-mation sufficient to warrant the diag-nosis, the diagnosis was given and be-came the diagnosis of record.

The sample was divided into threegroups. Group 1 consisted of the 20persons with a psychiatric diagnosis ofschizophrenia, all of whom also hadelevated scores on the schizophreniasubscale of the DASH-II. They had

Brief Reports

The authors are affiliated with the depart-ment of psychology at Louisiana StateUniversity. Address correspondence toDr. Cherry, Department of Psychology,Louisiana State University, Baton Rouge,Louisiana 70803-5501 (e-mail, pskatie@lsu.edu).

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no psychiatric diagnoses other thanschizophrenia. Group 2 consisted of20 persons whose schizophreniascore on the DASH-II was similarlyelevated but who did not warrant apsychiatric diagnosis of schizophre-nia. Group 3, the control group, con-sisted of 20 persons with no signifi-cant elevations on any of the DASH-II subscales and no psychiatric diag-nosis of any kind. We conducted aone-way analysis of variance of thefrequency scores of the schizophreniasubscale. (Extensive information onthe demographic and health charac-teristics of the sample as well as themethod of administration, scoring,and psychometric properties of theDASH-II are available from the au-thors on request.)

Next we conducted a frequencycount of symptoms taken from thepsychiatric reports of the subjects ingroup 1, those with a diagnosis ofschizophrenia and an elevated schizo-phrenia subscale on the DASH-II.We organized these symptoms ac-cording to three of the four factors ofschizophrenia phenomenology de-scribed by Lenzenweger andDworkin (4) reality distortion, neg-ative symptoms, and disorganization;we omitted the fourth factor, premor-bid social functioning, because the in-formation for it was not available.

Results and discussionA one-way analysis of variance of thefrequency scores of the schizophreniasubscale showed that differences be-tween the three groups were statisti-cally significant (means were 5.11,3.09, and .38 for groups 1, 2, and 3,respectively; F=73.41, df=2, 57, p