Schizophrenia Daily News Blog

Family-based clusters of cognitive test performance in familial schizophrenia

Authors: Fabian Hoti, Annamari Tuulio-Henriksson, Jari Haukka, Timo Partonen, Lasse Holmstrom and Jouko Lonnqvist

BMC Psychiatry, 4(20), July 2004

Previous studies have shown that schizophrenia results in impairments on some neuropsychological tests involving attention, memory, executive functioning, and intelligence. As a result, traits derived from neuropsychological tests have been suggested as one type of endophenotype, which is an expression of an underlying genetic vulnerability. This study is the first to use a new visually aided clustering approach (for statistical analysis) to look at cognitive performance of families as well as individuals with schizophrenia.

The authors gave neuropsychological tests to 54 randomly selected families where at least two siblings had schizophrenia. They found three types of clusters - well-performing, impaired, and intermediate clusters. In the well-performing cluster, both patients and family members received the highest scores in each cognitive test. The intermediate cluster scored consistently between the impaired and well performing cluster. However, clusters of families did not differ from each other in age, sex distribution and other clinical features. The well-performing cluster was significantly more educated than the others, but controlling for education years did not change the main results. This finding brings up the issue that further research is needed to identify factors that protect cognitive development in some people. But, from this study it seems that it may be possible to identify high risk for future schizophrenia by using multiple cognitive measures as possible endophenotypes.

However, this study is limited since it only included families where multiple individuals suffered from schizophrenia, which represents only about one fifth of all schizophrenia cases. So, the results may not be generalizable to families where there is only one person suffering from the illness. Also, the set of neuropsychological measures that were used did not cover all the cognitive domains that previous studies have suggested as endophenotypes. The lack of a control group also prevents testing the possibility that the same clustering solution could also emerge in families where there is no schizophrenia. Nevertheless, this study provides further support for the use of cognitive traits as valid endophenotypes to be used in genetic studies of schizophrenia.

Abstract: Family-based clusters of cognitive test performance in familial schizophrenia

Author: szadmin