Schizophrenia by people with mental disability has athe name PROPFSCHIZOPHRENIA. The clinical picture is very poor and simillar to residual or "negative" form of Schizohrenia. Many of this are chronic organic psychosyndroma with psychotic or nonpsychotic future (symptomatisc psychosis, secondary Schizophrenia).

Thank you.

Muhammad

Dear Muhammad,

The highland genetic  isolate that I mentioned in my message has exactly such clinical phenotypes -many of affected have co-morbidities of schizophrenia and intellectual disability. I studied geneology and demographical history of the isolate and found that two different by origin ancestral groups founded this isolate about 700 years ago. With detailed clinical study using not only Russian/Dagestan psychiatric hocpital Dxs but also DSM-IV based DIGS surveys we were able to separate descendents of these two founders with approximately higher schizophrenia aggregation and second- with predominant ID aggregation...and third part of affected -with comorbodities of ID and SCZ that in their geneology had inter-kindred marriages of above pedigrees. This amazing segregation is not really segregation as we usually understand-observed picture in clinical phenotypes we have because of highlanders in the isolates are keeping a strong tranditional consanguinoues marriages within pedigrees of two different founders. Only in last 5-7 generations members there started inter-kindred marriages. The clinical picture for SCZ sometimes mild and  age of manifestation 16-18, while ID symptoms are clear from early childhood.  I have genome-scan of all affecteds in their healthy families members using STRs and AFFX SNP 5 and we [erformed linkage, haplotypes, CNV and ROH for all types of clinical phenotypes there.. We can discuss in details about our results of analyses there if you are interested.

Kazima

Thank you for detailed answer. Where is this work published?

Muhammad

We published just short Letter in J. Open Genomics, 2013, and only 12q haplotypes and linkage findings in ID pedigree from the isolate in the invited paper published at NPG 2005 - I will send to you them. Most the  results are not published yet -working on the papers preparations

Hi Muhammad,

some of the key publications on this:

Turner, T. H. (1989). "Schizophrenia and mental handicap: an historical review, with implications for further research." Psychological Medicine 19(2): 301-314.

The relationship between schizophrenia and 'mental handicap' has been obscured by historical changes and varying diagnostic criteria. It has been generally accepted that there is an increased incidence of psychotic illness among people with intellectual retardation, but detailed community surveys are limited. Catatonia, severity of illness and research potential are all to be found in this 'dual diagnosis' group. The value of an historical analysis is underlined.

Morgan, V. A., et al. (2008). "Intellectual disability co-occurring with schizophrenia and other psychiatric illness: population-based study." British Journal of Psychiatry 193(5): 364-372.

BACKGROUND: The epidemiology of intellectual disability co-occurring with schizophrenia and other psychiatric illness is poorly understood. The separation of mental health from intellectual disability services has led to a serious underestimation of the prevalence of dual diagnosis, with clinicians ill-equipped to treat affected individuals. AIMS: To estimate the prevalence of dual diagnosis and describe its clinical profile. METHOD: The Western Australian population-based psychiatric and intellectual disability registers were cross-linked (total n=245,749). RESULTS: Overall, 31.7% of people with an intellectual disability had a psychiatric disorder; 1.8% of people with a psychiatric illness had an intellectual disability. Schizophrenia, but not bipolar disorder and unipolar depression, was greatly over-represented among individuals with a dual diagnosis: depending on birth cohort, 3.7-5.2% of those with intellectual disability had co-occurring schizophrenia. Pervasive developmental disorder was identified through the Intellectual Disability Register and is therefore limited to individuals with intellectual impairment. None the less, pervasive developmental disorder was more common among people with a dual diagnosis than among individuals with intellectual disability alone. Down syndrome was much less prevalent among individuals with a dual diagnosis despite being the most predominant cause of intellectual disability. Individuals with a dual diagnosis had higher mortality rates and were more disabled than those with psychiatric illness alone. CONCLUSIONS: The facility to combine records across administrative jurisdictions has enhanced our understanding of the epidemiology of dual diagnosis, its clinical manifestations and aetiological implications. In particular, our results are suggestive of a common pathogenesis in intellectual disability co-occurring with schizophrenia.

P. Jones, B. Rodgers, R. Murray, M. Marmot

Child development risk factors for adult schizophrenia in the British 1946 birth cohort

Lancet, 344 (1994), pp. 1398–1402

J.B. Kirkbride, P. Fearon, C. Morgan, P. Dazzan, K. Morgan, J. Tarrant, et al.

Heterogeneity in incidence rates of schizophrenia and other psychotic syndromes: Findings from the 3-center AeSOP study

Arch Gen Psychiatry, 63 (2006), pp. 250–258

Thanks Andrew. These references are very helpful.

Muhammad