Beliefs that are bizarre, baffling and seemingly unsupported by evidence are referred to as delusions and are a hallmark of the most severe mental illnesses. Yet, it is possible to hold perfectly sane beliefs that others might regard as irrational. New brain imaging data suggests that while odd beliefs and delusions may exist on a continuum, the extent to which a belief evokes stress could be a crucial distinction.
The research is published online ahead of print in the journal Neuropsychologia.
"Our study suggests that that for individuals who hold strange beliefs but are not distressed by them, the brain signal is distinct from what is found in people with psychotic mental illness," said Philip Corlett, PhD, assistant professor of psychiatry at Yale School of Medicine, and the study's lead author. "However, if the belief begins to pervade one's world-view and engender distress, there is a shift toward more pathological brain and behavioral responses."
The researchers had previously observed that activity in the brain's right dorsolateral prefrontal cortex predicts delusion severity in patients with psychosis. Having developed this neural marker of the processes underlying delusions, the researchers sought to explore whether similar alterations would be found in healthy, non-psychotic volunteers expressing beliefs that are, qualitatively, considered similar to those that characterize mental illness.
As part of this study, participants completed questionnaires that captured the number of odd beliefs they endorsed and whether they were convinced, preoccupied or distressed by those beliefs.
Study participants were asked if they believed in the power of witchcraft and mental telepathy, or if they felt there is a conspiracy against them. A commonly endorsed belief was, “People can make me aware of them just by thinking about me."
Studies using the same questionnaires in patients with delusions found that although healthy people often endorsed as many unusual ideas as patients, those with clinical delusions were more distressed about their beliefs.
The researchers then correlated the predominance and nature of the beliefs with brain activity associated with delusions. The results suggest that there may be a separate mechanism through which unusual ideas and beliefs might remain benign and might even enrich people's lives. However, healthy subjects whose beliefs were held with greater conviction and accompanied by greater distress were more likely to show brain activity similar to patients with delusions.
Paul Fletcher, MD, PhD, the Bernard Wolfe Professor of Health Neuroscience at University of Cambridge, is senior author. This research was supported by the Wellcome Trust.