Electronic Letters to:
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eLetters: Electronic letters published:
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Re: Dual Diagnosis Quandries
- Vera A. Morgan, Assen V. Jablensky (2 April 2009)
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Dual Diagnosis Quandries
- Patricia Hogan (26 May 2009)
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Vera A. Morgan, Epidemiologist School of Psychiatry and Clinical Neurosciences, University of Western Australia, Assen V. Jablensky
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vmorgan{at}cyllene.uwa.edu.au Vera A. Morgan, et al.
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We thank Patricia Hogan for her comments challenging current definitions of intellectual disability (ID) and highlighting the difficulty of accurate assessment of psychotic illness in individuals with intellectual disability. With respect to the former, we note the importance of applying standard definitions and nomenclature in the study of the epidemiology of dual diagnosis. The criteria used to define ID affect prevalence rates and the use of IQ criteria alone rather than the dual criteria of IQ and adaptive behaviours will have a marked impact on rates (Whitaker, 2004). We employed the American Association on Mental Retardation dual criteria in our study. The use of dual criteria is the most common approach across services and in research, and is consistent with DSM-IV and ICD-10 definitions. As the American Association on Mental Retardation criteria are the basis of service eligibility in Western Australia, their use ensures a thorough assessment of individuals on the intellectual disability register and greater confidence that cases have been correctly classified in this study. While the difficulty of diagnosing psychosis accurately in individuals with intellectual disability is well-documented (Deb & Weston, 2000; Friedlander & Donnelly, 2004), our paper highlights another pressing issue. The poor recognition of dual diagnosis in affected individuals as a result of the administrative separation between ID and mental health services has led to a serious underestimate of the prevalence of dual diagnosis and has created structural impediments to inter-agency approaches to integrated, person-oriented clinical practice. Critical improvements are needed both in the structure of service provision and in clinical education programs to ensure dual diagnosis is correctly identified and appropriately treated (Bouras & Holt, 2004; Catinari, Vass, Ermilov, & Heresco-Levy, 2005). Otherwise dual diagnosis will continue to be recognised and treated ineffectively or, at worst, missed altogether, with important implications for best practice. Bouras N, Holt G: Mental health services for adults with learning disabilities. British Journal of Psychiatry 184:291-292, 2004. Catinari S, Vass A, Ermilov M, et al.: Pfropfschizophrenia in the age of deinstitutionalization: whose problem? Comprehensive Psychiatry 46:200- 205, 2005. Deb S, Weston S: Psychiatric illness and mental retardation. Current Opinion in Psychiatry 13:497-505, 2000. Friedlander R, Donnelly T: Early-onset psychosis in youth with intellectual disability. Journal of Intellectual Disability Research 48:540-547, 2004. Whitaker S: Hidden learning disability. British Journal of Learning Disabilities 32:139-143, 2004. |
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Patricia Hogan, Psychiatrist Family Guidance Center
Send letter to journal:
drpathogan{at}hotmail.com Patricia Hogan
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To Vera Morgan, Et al, authors of ?Intellectual Disability co- occurring with Schizophrenia and other Psychiatric Illness: Population- based study? [(2008) 193, 364-372], You have made a useful contribution in the area of intellectual disability/mental illness (ID/MI) dual diagnosis. However, this study, like most in this area, is flawed by inadequate definition of terms. ?Intellectual Disability?, the current phrase of fashion for this population, is unsatisfactory, because many individuals in the higher IQ ranges are not disabled. The American Association on Mental Retardation (now AAIDD) definition, probably the most widely used definition, is cited. It gets around the disability issue by requiring that ID individuals must also have ?limitations in adaptive behaviors and skills?. This confounds the ID and MI categories, as such limitations may well be mental illness. Perhaps a better term for studies to use would be ?intellectual impairment?, which, like visual impairment, does not necessarily imply disability. Then all individuals in certain IQ ranges could be included. As it is, a certain portion of the individuals without MI are excluded by the definition. This may inflate the prevalence rates. Additionally, there is a problem in lumping together all ranges of ID. As you note, MI, particularly schizophrenia is more likely to be diagnosed in the Borderline group and Pervasive Developmental Disorder (PDD) is more likely to be diagnosed in the severe/profound group. Rather than a true reflection of incidence, this may reflect a nosological bias. A strict definition of Schizophrenia is difficult to apply to a non-verbal person. Historically, PDD and schizophrenia have sometimes been used interchangeably in apparently disturbed and non-verbal individuals, but since the 1990s, at least in the US, there has been a massive shift towards the diagnosis of PDD subcategories, such as autism and Asperger?s. The diagnosis of schizophrenia has an additional stigma which some families find unacceptable. The authors found some trends distinguishing dual diagnosis individuals from those with ID alone. Some of these trends also distinguished borderline from other levels of ID (fewer genetic causes, less Down syndrome, less epilepsy, etc). To distinguish Dual diagnosis from ID alone, probably results should be controlled for IQ level. You have considered dual diagnosis patients to have more severe MI than other MI patients as indicated by number of hospitalizations, length of hospitalizations, etc. Perhaps this just indicates that treatment and placement options for these patients are poorer. Future studies need to be done to clarify the unique aspects of this population. Patricia E. Hogan, D.O., Psychiatrist |
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