Siblings of people who have schizophrenia are more likely than healthy control subjects to have social anhedonia, to withdraw from social contact, and to report having psychotic experiences, according to a report published online in Schizophrenia Research.
"Our findings suggest that the overlap between [social anhedonia], withdrawal, and positive symptoms ... may ... reflect a shared genetic vulnerability, instead of merely being either a state marker of – or reaction to – psychotic symptoms," said Eva Velthorst of the University of Amsterdam and her associates (Schizophr. Res. 2012 April 30 [doi:10.1016/j.schres.2012.03.022]).
For many years, social disinterest was recognized as a central feature of psychosis vulnerability, Ms. Velthorst and her colleagues wrote. These study results suggest that social anhedonia could be a significant factor in the pathway to psychosis, and that people who develop this cluster of symptoms might be at increased susceptibility for a first psychosis, added Ms. Velthorst, a Ph.D. candidate at the university.
The investigators examined the relationship among social anhedonia, withdrawal, and psychotic experiences using data from a multicenter longitudinal study of people aged 16-50 years residing in the Netherlands and Belgium. They assessed a subgroup of 646 unaffected siblings of schizophrenia patients and 326 healthy controls. Exclusion criteria for healthy controls were a history of psychotic disorder or having a first-degree family member with such a history.
The study subjects were assessed for social anhedonia and withdrawal using the Structured Interview for Schizotypy-Revised, and for psychotic experiences using the Community Assessment of Psychic Experiences. The CAPE, a self-report questionnaire, covers social delusions such as feeling persecuted, bizarre experiences such as receiving messages from the television, and popular beliefs such as believing in telepathy or voodoo.
A small but significant association was found among the three symptoms in the sibling group but not in the control subjects, suggesting that social anhedonia and withdrawal might be a marker of vulnerability to psychosis.
"Further prospective research is needed to clarify how [social anhedonia], withdrawal, and positive symptoms interact precisely in the trajectory to a first psychosis, and such research may eventually contribute to a better psychosis prediction," Ms. Velthorst and her colleagues said.
Future research also could open the door to possible interventions, testing whether social activity and engagement reduce the likelihood of progressing to a first psychotic episode, they added.
This study was supported by the Dutch Health Research Group, Lundbeck, AstraZeneca, Eli Lilly, and Janssen-Cilag. No financial conflicts of interest were reported.