May 8, 2013

expert reaction to maternal influenza and bipolar disorder

Maternal influenza during pregnancy may be a risk factor for bipolar disorder in their offspring, suggested a study published in JAMA Psychiatry.

Professor Robin Murray, Professor of Psychiatric Research, Institute of Psychiatry, King’s College London, said:

“The idea that prenatal exposure to influenza might increase the risk of serious mental illness has a long history. There was a great deal of interest in this in relation to schizophrenia some 20 years ago.   However it was never possible to demonstrate this definitively.  If it is a risk factor then it is so only for a very small proportion of schizophrenia. 

“Now this paper looks at the same question in Bipolar Disorder and comes up with positive findings.  The study appears to be well done but of course the sample is small.    We should wait for a replication before we get excited. Certainly we should not alarm pregnant ladies about this possible risk when they so much else to worry about.”

Dr Fiona Gaughran, Lead Consultant Psychiatrist, National Psychosis Service, South London and Maudsley NHS Foundation Trust and Hon Senior Lecturer, King’s College London’s Institute of Psychiatry, said:

“This highly-regarded group of researchers has reported similar links between schizophrenia and various maternal infections. If future work confirms the link reported here, policy makers may need to consider implications for flu prevention pre-pregnancy, but mothers need not be worried. The overall risk of offspring developing bipolar disorder is low even if one did get flu in pregnancy.”

Dr Daniel J. Smith, Reader in Psychiatry, Institute of Health and Wellbeing, University of Glasgow, said:

“This is an interesting study which identifies maternal infection with influenza during pregnancy as a potential risk factor for the later development of bipolar disorder in offspring.  To some extent this finding is unsurprising given that maternal influenza has already been identified as a risk factor for the development of schizophrenia (and we know that schizophrenia and bipolar disorder have many genetic and environmental risk factors in common).  It will be very important for this finding to be replicated in similar large-scale longitudinal studies and it is worth noting that only a minority of the bipolar individuals in this study (8.7%) were born to mothers who had been exposed to influenza during pregnancy, so it is likely that many additional risk factors are necessary to cause bipolar disorder.”

Dr Paul Keedwell, Clinical Lecturer in the Neurobiology of Mood Disorders and Honorary Consultant Psychiatrist, Institute of Psychological Medicine and Clinical Neurosciences, MRC Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, said:

“This study suggests that individuals who were exposed to the influenza virus while in the womb have an almost fourfold increase in risk for bipolar disorder. Although the study needs replicating in a larger sample, it is further evidence of the complex interplay between environment and genes in the genesis of this often disabling disorder. Exposure to flu in utero also increases the risk of schizophrenia, suggesting that the two disorders may share some abnormalities of brain development. If we can work out how the flu virus affects the developing brain we might be able to understand the biological basis of these major mental disorders more broadly.”

Dr James MacCabe, Senior Lecturer, Department of Psychosis Studies, King’s College London’s Institute of Psychiatry, said:

“These findings are potentially important but require replication. The study was conducted to the highest standards given the limitations of the data available. Of 92 individuals with bipolar disorder in adulthood, eight were found to have been exposed to influenza in pregnancy. This is nearly four times the expected number, but the role of chance cannot be ruled out.

“Two previous findings add credence to the results: firstly, previous research has found that exposure to influenza in pregnancy carries an increase in risk for schizophrenia, which shares some genetic overlap with bipolar disorder. Secondly, this is not the first study to report that problems with pregnancy may increase the risk of bipolar disorder in adulthood: a study last year published in the same journal, found an association between pre-term delivery and later bipolar disorder. 

“If these results are replicated in other samples, our next challenge is to understand how problems in pregnancy can influence the risk of bipolar disorder, decades later.  

“The Department of Health already advises pregnant mothers in the UK to have seasonal flu vaccination, primarily to protect the mother’s health, and women should continue to follow this guidance.”

Dr Fiona Lobban, Senior Lecturer in Clinical Psychology, Spectrum Centre for Mental Health Research, Lancaster University, said:

“The authors quite rightly identify limitations of previous research in this area and carry out an ambitious attempt to remedy some of these. However, there were 8 of 92 people with Bipolar Disorder who had a mother who had influenza in pregnancy and 19 of 722 people without Bipolar Disorder who had a mother with influenza in pregnancy. These are very small numbers.

“Even though the risk of influenza is greater in the Bipolar Disorder group, only 7% of people with Bipolar Disorder had a mother with influenza – therefore 93% of people didn’t.

“In summary, 93% of people with Bipolar Disorder never had a mother with influenza during pregnancy so of all the things pregnant woman are told to worry about, this should not be one of them”

Dr Warren Mansell, Reader in Clinical Psychology
, School of Psychological Sciences, University of Manchester, said:

“There are many known risk factors for mental health problems and so this finding is not surprising. Some are infectious agents, some are genes but many are life events such as childhood trauma and domestic abuse. But a risk factor is just that – it raises the chances of developing a mental health problem – it does not cause it. This research risks shifting the emphasis away from helping people with mental health problems right now, with the right community support and NHS-recommended psychological therapies that we know work.” 

‘Gestational Influenza and Bipolar Disorder in Adult Offspring’ by Parboosing et al., published in JAMA Psychiatry on Wednesday 8th May.