Background. Prior studies suggest familial (possibly genetic) influences on the course of schizophrenia. Aims. The aim of this study was to compare familial influences on the course and severity of schizophrenia in two independent samples. Method. Thirteen selected measures were compared among affected sibling pairs (ASPs) from Pittsburgh, USA and New Delhi, India (48 US pairs, 53 Indian pairs). For each ASP proband, an unrelated patient was selected randomly from a suitable pool of cases ascertained in the same study (Sibpair proband - comparison case or S-C pairs). Correlations between these pairs were compared. Results. The correlations varied by item and by site. Significant correlations for longitudinal course and pattern of severity were noted among the ASPs from USA, but did not remain significant following corrections for multiple comparisons. Comparisons between the correlations for ASPs and the S-C pairs, used to estimate familial effects, yielded trends for the ASP correlations to be numerically larger than the S-C correlations in both samples. Separate cross-site comparisons revealed several significant differences with regard to several demographic and clinical variables. The possible impact of the cross-site variations on the observed ASP correlations is discussed. Conclusions. Though familial factors did not appear to have a significant impact on course/severity using this novel design, the suggestive trends need to be examined in larger samples.
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■ Acknowledgements We thank two anonymous referees for their helpful comments. This work was supported in part by grants from the NIH (MH01489, MH56242 and MH53459, R03 TW00730 and Indo-US Project Agreement # N-443–645). We thank the following colleagues for help with ascertainment in India. B. R. Angnihotri, K.M.Aggarwal,K.Arora,M.Batra,V.Bhaskar,R.Bhatia,N.Bohra,R.K. Chadha, P. L. Chawla, A. K. Das, S. K. Das, U. Goswami, A. K. Gupta, G. Gupta, R.C. Jiloha, U. Khastgir,A. Kumar, K. Kumar,A. Lal, D.N. Man-dekar, H. Matai, M. N. L. Mathur, S. Mittal, J. Nagpal, R. Nagpal, H. C. Raheja, A. K. Sharma, R. A. Singh, R. K. Singh, S. Nodiyar, P. Dwivedi, Ms. Sushma, Mrs.M. Zutshi, N. Prakash, B. Singh and J.Yadav.
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