In the first ever study utilizing magnetic resonance imaging (MRI) to examine brain structure in women at risk for postpartum psychosis (PP), Fusté et al. compare scans across women at risk for PP who have experienced a postpartum psychotic episode (PPE), women at risk who have not experienced a postpartum psychotic episode (NPPE), and healthy controls (HC). PP is quickly becoming an area of interest within the field of perinatal psychiatry due to its significant contribution to maternal morbidity. However, its relatively low prevalence and diversity of presentations has posed a challenge to studying the disorder in a rigorous, controlled manner. Research that has been conducted to date has largely dealt with clinical presentation, treatment, or genetic factors, and there is a lack of understanding of the neurological basis for PP. This study, while preliminary in its findings, begins to bridge this knowledge gap and contributes meaningfully to the body of research surrounding PP.
While rare at a prevalence of only 1-2 per 1000, postpartum psychosis is highly predictable. Certain groups are at a much higher risk of experiencing a postpartum psychotic episode including women with schizoaffective disorder or bipolar affective disorder, women with a previous history of PP, and women with both bipolar disorder and a family history of PP. The Fusté et al. study used these criteria to recruit 26 women at risk for PP. Of this group, n=11 women had experienced an episode of postpartum psychosis (PPE) and n=15 women had not (NPPE). As a healthy control (HC) group, 21 women in the same postpartum period were recruited who were matched to the risk group according to age, parity (number of pregnancies reaching gestational age), and ethnicity.
Previous research on the brain structure of people with affective psychoses such as schizoaffective disorder and bipolar disorder have shown decreased size of the anterior cingulate cortex (ACC) and paralimbic regions, which deal with emotional processing. Since a diagnosis of an affective psychotic disorder is a risk factor for developing PP, it is not surprising that many of the same brain regions were examined in this study. The brain regions of interest for this study were the ACC, postcentral gyrus, bilateral inferior and frontal gyrus, superior temporal gyrus (STG), hippocampus, and para-hippocampal gyrus. Using MRI, the cortical thickness (CTh) and cortical surface area (CSA) were examined. Additionally, the researchers performed voxel-based morphometry to get a sense of the gray matter, white matter, and cerebrospinal fluid composition and volume of the areas scanned. The results were compared across groups (PPE, NPPE, and HC).
The results of this study indicate that there may be different morphologies for various clinical phenotypes of women at risk for PP, as evidenced by the different patterns between the PPE and NPPE groups. Generally, women in the PPE group showed smaller volume in the ACC, left para-hippocampal gyrus, left STG, and postcentral gyrus at a trend level (not statistically significant, but showed a trend). Women in the NPPE group showed larger left superior and inferior frontal gyri than women in the HC group and those in the PPE group, at a trend level. CTh and CSA were measured in areas that differed in volumes based on the results of the voxel-based morphometry. Women in the PPE group showed smaller CSA than women in the NPPE group in the left para-hippocampal gyrus, ACC postcentral gyrus, and left STG, although the differences between groups in CSA in the postcentral area and STG were not significant. Overall, women who had experienced an episode of postpartum psychosis showed smaller volumes in key areas of interest as compared to women with the same or similar risk factors for PP who had not experienced an episode of psychosis in the postpartum period.
The results of this study show overlap of brain areas associated with PP and those associated with other affective psychoses, as predicted. For example, the finding that women in the PPE group had smaller volumes for the ACC is consistent with research on people with or at risk for affective psychosis. However, the reduction in volume for the PPE group of this study was observed in the dorsal region of the ACC, as opposed to reduction in the subgenual region that has been reported for other psychotic disorders. This points to the possibility of diagnosis-specific morphological changes that distinguish PP from other psychoses.
The observed increase in volume for many of the regions of interest in women in the NPPE group could reflect a protective effect or could be due to the significant structural changes in the brain associated with pregnancy and motherhood. Additionally, this result could reflect medication-induced effects as women in the NPPE group generally had a longer duration of illness and thus were likely to be on medication for longer than those in the PPE group.
In addition to understanding more about the underlying cause of PP, studying the brain regions and changes associated with the disorder could lead to earlier diagnosis and identification of women at high risk for developing PP. There is evidence to support that people without psychosis but who are at an elevated risk for developing a psychotic disorder or episode already exhibit some of the brain changes associated with the disorder before the onset. This has not necessarily been confirmed in women who develop PP, and further longitudinal research will need to be performed to gain a better understanding of whether neurological changes can act as predictive biomarkers for PP. However, this research provides a promising starting point for understanding how PP develops and will hopefully lead to better diagnostic and predictive tools.
Research summary compiled by Nicola Roux.
Fusté, Pauls, Worker, Reinders, Simmons, Williams, . . . Dazzan. (2017). Brain structure in women at risk of postpartum psychosis: An MRI study. Translational Psychiatry, 7(12), 1286.