Robert J. Pary, M.D. Associate Professor of Psychiatry Southern Illinois University, School of Medicine P.O. Box 19230 751 Rutledge Street Springfield, IL 62794-9230 The Habilitative Mental Healthcare Newsletter 1993, Vol. 12, p. 26-7 © 1993 Pysch-Media, Inc.

Reprinted with permission of Psych-Media, Inc., publishers of Psychiatric Aspects of Mental Retardation Reviews, Habilitative Mental Healthcare Newsletter, and the journal Mental Health Aspects of Developmental Disabilities. Editor-in-Chief: Anne D. Hurley, Ph.D E-mail: mhdd@emji.net P.O. Box 57 Bear Creek, NC 27207-0057 (336) 581-3700 Fax: (336) 581-3766

Limitations In Diagnosing Psychiatric Disorders
     Before discussing the findings, it may be helpful to mention potential limitations in diagnosing psychiatric disorders in persons with MR because this can be difficult⁵. Individuals with moderate or severe MR usually cannot accurately inscribe their thoughts and perceptions. Such descriptions are often required in using a diagnostic schema such as the Diagnostic and Statistical Manual, Third Edition -Revised (DSM-III-R)¹. Persons with mild mental retardation, however, can often accurately respond to questions about feelings, perceptions and thoughts. Thus, the DSM-III-R categories can be used with more confidence. The International Classification of Disorders (ICD) is more flexible in the clinical guidelines, though difficulties still can occur in trying to diagnose psychiatric disorders in persons with IQ's below the mild range. Therefore, when reviewing studies of psychiatric disorders in persons with MR, it is useful to know: a) how many persons had intelligence testing and b) the percentage with mild MR versus moderate, severe and profound retardation.
     In Lund's³ study, "few" persons had mild MR and none had borderline intellectual functioning. Whereas in the Myers and Pueschel's study⁴, 182 (77%) of the adults had intelligence levels established and 17 of them (9%) had mild MR. In Collacott et al's study², level of MR was not listed. Thus, the vast majority of adults with DS in all three studies were functioning at a level that made specific psychiatric diagnoses difficult.

Prevalence of All Psychiatric Disorders
     Despite not knowing the validity of the psychiatric diagnoses, the three studies provide some useful clinical information. Though the studies did not all define psychiatric disorders in the same way, it is striking that the three research groups all found that 25-26% of adults with DS have a psychiatric disorder. (This figure includes individuals diagnosed with dementia, which will be discussed separately in a later column.)
     The studies also included diagnoses not found in DSM-III-R such as behavior problems⁴ and aggressive and self-injurious behavior². In the latter case, the Myers and Pueschel specified that the aggression was "persistent assaultive behavior not fitting conduct or impulsive disorder".
     Furthermore, aggressive behavior was the most frequent "psychiatric" disorder (8%) in their adult population. If aggressive behaviors are eliminated, it is not known whether the total percentage of psychiatric disorders would change because some individuals had more than one psychiatric diagnosis.
Unfortunately, an observation by Lund could neither be confirmed nor disproved by the other two studies. Lund found that 8 of the 11 persons with a psychiatric disorder were male. Although the male/female (2/2) for dementia was equal, four out of five individuals with autism were male and both persons with a behavioral disorder were male. Given the small sample in Lund's study, it remains to be proven that adult males with DS have significantly more psychiatric disorders.

Autism
     Lund found that 5/44 (11%) of his subjects had autism. This finding was not confirmed in either of the other two studies. Myers and Pueschel diagnosed 2/236 (0.8%) to have autism and Collacott's group 8/371 (2.2%).

Depression
     As with autism, Lund's findings are counter to the other two studies. Not one of the 44 persons in Lund's study were diagnosed with depression. Myers and Pueschel found sufficient evidence in the charts to diagnose major depression based on DSM-III-R criteria in 10 out of 164 (6.1%) adults with DS who were seen at an outpatient clinic. None of the charts from 72 adults (29 - 72 years) residing in a state school met DSM-III-R criteria for major depression.
     Collacott's group matched individuals with DS by age, sex, and residential setting (but not intelligence level) to persons with MR from a cause other than DS. Collacott used a different set of criteria for depression (International Classification of Disorders, 9th edition [ICD-9]) and lumped major depression and minor depression. Not only did this group find 42 adults with DS out of 371 (11.3%) with depression, but also the persons with DS had significantly more depression (<.001) than the control group.

Schizophrenia
     Neither Lund nor Myers and Pueschel found anyone with schizophrenia among a combined 280 adults with Down syndrome. Collacott's group diagnosed 6 out of 371 (1.6%) with schizophrenia or paranoid states. One could argue that the percentage is probably similar to the prevalence of schizophrenia or paranoid states in the general population. When Collacott's group compared schizophrenia/paranoid states in DS and control groups, the DS group had significantly fewer (<.01) persons diagnosed with these disorders. Thus, all three studies support the clinical impression that schizophrenia is less common in DS than in persons with other causes of MR.

Conclusion
     Despite differences in defining psychiatric disorders, as well as the limitations in applying criteria to adults with lower intellectual functioning, the three studies agree that:

1. one in four adults with DS has a psychiatric disorder (including dementia);
2. schizophrenia is less common persons with DS than in those with other causes of MR;
3. two studies, which included the large majority of subjects (607/651), found an increase in depression in association with DS.

1. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Third Edition - Revised. Washington DC: American Psychiatric Association, 1987.
2. Collacott RA, Cooper SA, McGrother C. Differential rates of psychiatric disorders in adults with Down's syndrome compared with other mentally handicapped adults. Br J Psychiatry 1992:161:671-674.
3. Lund J. Psychiatric aspects of Down's syndrome. Acta Psychiatr Scand 1988:78:369-374.
4. Myers, BA, Pueschel SM. Psychiatric disorders in persons with Down syndrome. J Nerv Nent Dis 1991:179:609-613.
5. Sovner R. Limiting factors in the use of DSM-III criteria with mentally ill/mentally retarded persons. Psychopharmacol Bull 1986:22:1055-1059.

Dr. J. Lund
Institute of Psychiatric Demography
Psychiatric Hospital in Aarhus
Risskov, Denmark

Dr. Beverly A. Myers, M.D.
Child Development Center
Rhode Island Hospital
595 Eddy St.
Providence, RI 02902

Dr. Richard A. Collacott
Frith Hospital
Groby Road Leicester, England LE3 9QF.