Researchers highlight blind spots in dual diagnosis of schizophrenia and personality disorder

A new study by a research team at Université de Montréal highlights a critical lack of knowledge about the cognitive profiles of people living with both schizophrenia and a personality disorder. 

A comprehensive review of scientific literature from the past 24 years, published in Schizophrenia Research: Cognition, reveals that despite the high prevalence of this dual diagnosis (affecting approximately 40 per cent of people diagnosed with schizophrenia) and its association with unfavourable outcomes, the available data are surprisingly limited and fragmented. 

Our analysis shows a significant blind spot in current knowledge. Little is known about cognition in people living with a personality disorder in addition to schizophrenia." 

Anouck Chalut, lead author of the study and a Psy. D. in neuropsychology from UdeM

Led by UdeM psychology professor Tania Lecomte-director of L'ESPOIR, a research laboratory in the Department of Psychology dedicated to improving treatments and services for people with severe mental disorders-the researchers combed through hundreds of scientific articles but found only 10 that met their criteria for scientific rigour. 

"We found that the existing research is limited, fragmentary and sometimes contradictory, leaving clinicians with few clear guidelines," noted Chalut. This gap is consequential because cognition is the strongest predictor of recovery for individuals living with schizophrenia, she said. 

Significant health challenges 

The combination of schizophrenia and a personality disorder presents considerable challenges, including more severe psychotic symptoms, serious functional impairment, reduced compliance with medication, more frequent hospitalization and increased risk of suicide. 

Despite these challenges, people with this dual diagnosis are often excluded from clinical studies or grouped together with patients who have only schizophrenia. 

"Our findings underscore the need to improve our understanding of these individuals and focus on their cognitive profiles to support functional recovery, given that cognition plays a decisive role in that process," said Chalut. 

The study offers concrete recommendations for both clinicians and researchers, including systematic screening for symptoms of personality disorders in people living with schizophrenia and the use of standardized tools to characterize cognitive profiles in this population. 

The research highlights the need for further investigation into adapting treatments and therapies to the specific needs of these individuals, who are often overlooked in current research, the study team argues. 

Approaches such as cognitive remediation – which aims to mitigate the effects of cognitive deficits and support strategies to strengthen impaired mental abilities, including memory, attention and problem-solving – could prove useful, the researchers believe.