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The recent article by Harlow and colleagues1 undoubtedly adds to our understanding of the risk factors for severe postpartum disorders. The study reaffirms that women with a history of psychiatric admission are vulnerable to further episodes in relation to childbirth and finds that the number of previous episodes and time since last admission are important in determining the magnitude of an individual's risk.
In one important respect, however, the results presented give rise to misleading conclusions. The study suggests that the risk of postpartum psychosis is higher among women with a history of schizophrenia than women with previous episodes of bipolar disorder. This is in stark contrast to previous studies2 - 6 and to the experience of clinicians working in perinatal psychiatric services so it is imperative to consider what accounts for this difference.
A close examination of the methods used reveals several factors that could serve to underestimate the risk to women with bipolar disorder and overestimate the risk in women with schizophrenia.
The inclusion of women with an International Classification of Diseases, Eighth Revision or ICC-9 diagnosis of affective psychosis (code 296 and its subcategories) is likely to have resulted in a considerable proportion of women with unipolar depression in the “bipolar” group. This would be consistent with the more than 3-fold difference in the number of women with a history of a bipolar admission compared with admissions with schizophrenia (786 and 276 respectively)—a surprisingly large disparity given the approximately equal lifetime prevalence of these disorders when using DSM-IV definitions of schizophrenia and bipolar I disorder. Because the risk of severe episodes in the postpartum period is considerably lower in unipolar depression, this would have resulted in a significant underestimate of the true risk to women with bipolar disorder.
Admission in the postpartum period is not a reliable indicator of postpartum psychosis as the term is usually used (ie, the acute onset of a new [but not necessarily first] episode of psychosis or mania immediately following childbirth). Admission can occur for a number of reasons. In particular, women with a chronic psychotic illness such as schizophrenia are commonly admitted for assessment of parenting or because the stress of coping with a newborn baby affects an existing illness. The proportion experiencing the acute onset of a postpartum psychosis is likely to be considerably lower.
The introduction of antipsychotics with less impact on fertility has resulted in more women with a history of schizophrenia becoming mothers. Inevitably, some of these women require admission in pregnancy and the postpartum period. However, it is women with bipolar disorder who are at a particularly high risk of a postpartum psychosis being triggered by delivery. The magnitude of risk to women with bipolar disorder is underlined by another large registry study5 from Scandinavia, which found the relative risk for an admission with bipolar disorder in the month following first pregnancy deliveries to be 23—more than 4 times higher than the relative risk for admission with schizophrenia. Great caution is required in interpreting the findings of Harlow et al1 to avoid a misleading underestimation of this risk.
It is clear that research into postpartum psychosis has suffered because of the confusion in nosology and the inadequacy of diagnostic systems in relation to severe perinatal episodes of illness, a situation we hope that DSM-V and ICD-11 will address.
Correspondence: Dr Jones, Department of Psychological Medicine, University of Cardiff, The Henry Wellcome Building for Biomedical Research in Wales, Cardiff CF14 4XN, Wales (jonesir1@cardiff.ac.uk).
Financial Disclosure: None reported.
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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