Author Interviews, Cognitive Issues, JAMA, Schizophrenia / 26.07.2017
Genetic Risk of Schizophrenia May Contribute to Cognitive Dysfunction
MedicalResearch.com Interview with:
[caption id="attachment_36131" align="alignleft" width="180"]
Dr. Smeland[/caption]
Olav B. Smeland MD PhD
Postdoctoral researcher
SFF NORMENT, KG Jepsen Centre for Psychosis Research, Division of Mental
Health and Addiction, Oslo University Hospital & Institute of Clinical Medicine
University of Oslo Oslo, Norway
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: Schizophrenia is a severe mental disorder associated with widespread cognitive impairments. The cognitive deficits are associated with disabilities in social, economic and occupational functioning and lower quality of life among individuals with schizophrenia. Despite this, current treatment strategies largely fail to ameliorate these cognitive impairments.
To develop more efficient treatment strategies in schizophrenia, a better understanding of the disease mechanisms underlying cognitive deficits is needed. For a long time we have known that schizophrenia is heritable, and in recent years many schizophrenia risk genes have been identified. Moreover, several studies have indicated that genetic risk of schizophrenia may contribute to cognitive dysfunction.
In this study, we aimed to identify schizophrenia risk genes that also influence cognitive function. In a large international collaboration of researchers, we combined genome-wide association studies on schizophrenia and the cognitive traits of verbal-numerical reasoning, reaction time and general cognitive function. In total, we analyzed genetic data from more than 250.000 participants. We were able to identify 21 genetic variants shared between schizophrenia and cognitive traits. For 18 of these genetic variants, schizophrenia risk was associated with poorer cognitive performance.
Dr. Smeland[/caption]
Olav B. Smeland MD PhD
Postdoctoral researcher
SFF NORMENT, KG Jepsen Centre for Psychosis Research, Division of Mental
Health and Addiction, Oslo University Hospital & Institute of Clinical Medicine
University of Oslo Oslo, Norway
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: Schizophrenia is a severe mental disorder associated with widespread cognitive impairments. The cognitive deficits are associated with disabilities in social, economic and occupational functioning and lower quality of life among individuals with schizophrenia. Despite this, current treatment strategies largely fail to ameliorate these cognitive impairments.
To develop more efficient treatment strategies in schizophrenia, a better understanding of the disease mechanisms underlying cognitive deficits is needed. For a long time we have known that schizophrenia is heritable, and in recent years many schizophrenia risk genes have been identified. Moreover, several studies have indicated that genetic risk of schizophrenia may contribute to cognitive dysfunction.
In this study, we aimed to identify schizophrenia risk genes that also influence cognitive function. In a large international collaboration of researchers, we combined genome-wide association studies on schizophrenia and the cognitive traits of verbal-numerical reasoning, reaction time and general cognitive function. In total, we analyzed genetic data from more than 250.000 participants. We were able to identify 21 genetic variants shared between schizophrenia and cognitive traits. For 18 of these genetic variants, schizophrenia risk was associated with poorer cognitive performance.
















Dr. Kate Merritt[/caption]
Kate Merritt PhD
Post-Doctoral Research Worker
NOC Study (Nitric Oxide in Cognition)
Institute of Psychiatry
De Crespigny Park
London
MedicalResearch.com: What is the background for this study? What are the main findings?
Dr. Merritt: Research has indicated that levels of one of the main chemicals in the brain, glutamate, may be abnormal in schizophrenia. Almost sixty studies have measured glutamate levels in schizophrenia, however the findings are inconsistent, and it is thought that changes in glutamate levels may vary with the length or the severity of illness. This study therefore analysed all the published reports of glutamate in schizophrenia.
The main findings are that, overall, schizophrenia is associated with elevated glutamate in several brain regions; namely the medial temporal cortex, the basal ganglia and the thalamus. These changes also differed with the stage of illness; in the medial frontal cortex, glutamate was increased in people at risk for developing schizophrenia, but not in people who had been diagnosed with schizophrenia for several years, whereas in the medial temporal lobe the opposite pattern was detected.
Dr. Lena Palaniyappan[/caption]
Lena Palaniyappan
Medical Director
Prevention & Early Intervention Program for Psychoses (PEPP)
London, Ontario
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: It is now well established that patients with schizophrenia show reduced thickness of brain's grey matter in Magnetic Resonance Imaging studies, indicating either a developmental or an acquired deficit in the amount of brain tissue. Such reductions are seen both in treated and untreated patients, suggesting that current treatments do not reverse the process of tissue loss, if at all this is occurring in patients. We wanted to study if subtle increase in brain tissue also accompanied this reduction. We observed that across the group of 98 medicated patients, reduced thickness was consistently accompanied by subtle, but nevertheless noticeable increases in thickness. Such increases were more pronounced in those with a longer duration of illness.
Dr. Alan Brown[/caption]
Alan S. Brown, M.D., M.P.H.
Professor of Psychiatry and Epidemiology
Columbia University Medical Center
Director, Program in Birth Cohort Studies, Division of Epidemiology
New York State Psychiatric Institute
MedicalResearch.com: What is the background for this study? What are the main findings?
Dr. Brown: Smoking during pregnancy is a risk factor for several pregnancy-related outcomes including low birthweight and preterm birth. Evidence for a link with schizophrenia is scant. We analyzed a maternal biomarker of smoking called cotinine, a nicotine metabolite, in mothers of nearly 1,000 schizophrenia cases and 1,000 controls in a national birth cohort in Finland. We found that heavy smoking in pregnancy was related to a 38% increase in schizophrenia risk in offspring and that as cotinine levels increased even in the more moderate smokers risk of schizophrenia also increased.
Dr. Emily Severance[/caption]
Emily G. Severance, Ph.D
Stanley Division of Developmental Neurovirology
Department of Pediatrics
Johns Hopkins University School of Medicine
Baltimore, MD
MedicalResearch.com: What is the background for this study? What are the main findings?
Dr. Severance: This research stems in part from anecdotal dialogues that we had with people with psychiatric disorders and their families, and repeatedly the issue of yeast infections came up. We found that Candida overgrowth was more prevalent in people with mental illness compared to those without psychiatric disorders and the patterns that we observed occurred in a surprisingly sex-specific manner. The levels of IgG antibodies directed against the Candida albicans were elevated in males with schizophrenia and bipolar disorder compared to controls. In females, there were no differences in antibody levels between these groups, but in women with mental illness who had high amounts of these antibodies, we found significant memory deficits compared to those without evidence of past infection.




