Familial loading associates with impairment in visual span among healthy siblings of schizophrenia patients
Received 18 September 2002; received in revised form 13 December 2002; accepted 4 February 2003.
Abstract
Background
The effect of familial loading on neurocognitive deficits in relatives of schizophrenia patients has been detected in family and twin studies. The present study examined this effect among healthy siblings of schizophrenia patients in a Finnish isolate with high prevalence of schizophrenia.
Methods
We assessed performance in verbal and visual span tasks, in tests measuring intelligence, and in declarative verbal memory and learning tasks in 31 and 67 healthy siblings from families with one schizophrenia patient, or with two or more patients, respectively. The differences between the groups were tested using linear mixed effects models.
Results
An effect of familial loading was detected in the backward visual span task, measuring immediate visual memory with requirements from the visual domain of working memory. In this task, the healthy siblings from multiply affected families performed worse than those from the singleton families.
Conclusions
The finding that the multiplex vs. singleton differences were selective to the backward visual span task, strengthens the view that the visual domain of working memory may provide a valuable endophenotypic marker for genetic schizophrenia studies.
aDepartment of Mental Health and Alcohol Research (AT-H, RA, TP, JH, MS, JL), National Public Health Institute, Helsinki, Finland
bDepartment of Molecular Medicine (TV), National Public Health Institute, Helsinki, Finland
cDepartments of Psychology, Psychiatry and Biobehavioral Sciences, and Human Molecular Genetics (TC), University of California-Los Angeles, Los Angeles, California, USA
Address reprint requests to Annamari Tuulio-Henriksson, Lic.Phil., National Public Health Institute, Department of Mental Health and Alcohol Research, Mannerheimintie 166, 00300 Helsinki, Finland.
ABSTRACT