RESEARCH WEEKLY: March Research Roundup for World Bipolar Day
By Elizabeth Sinclair Hancq
Research Roundup is a monthly public service of the Office of Research and Public Affairs. Each edition describes a striking new data point about severe mental illness and summarizes recently published research reports or developments. This month’s roundup is in honor of World Bipolar Day.
DATAPOINT of the month
5.9 million individuals with severe bipolar disorder in the United States
There were approximately 5.9 million adults with severe bipolar disorder living in the United States in 2020. Approximately 51% of those individuals, or 3.0 million adults, are untreated at any given time. For more data on severe mental illness, including updated prevalence numbers based on the 2020 US Census, see our By the Numbers page.
RESEARCH of the month
Hypomania and bipolar disorder
Experiencing hypomania, defined as symptoms of mania that do not meet diagnostic criteria, can be a predictor for later developing bipolar disorder and therefore an important target to understand for early treatment and prevention. Further understanding the developmental course of bipolar disorder, including how much is due to genetics versus other effects, can help to inform why some with hypomania go on to develop bipolar disorder and others do not.
Utilizing data from a twin register in Sweden, researchers from University of London examined the genetic and environmental factors of hypomania and how those impacted later developing bipolar disorder. They found that 59% of hypomania symptoms could be explained by genetics in males, but only 29% in females, meaning there is more of a role of genetics in bipolar disorder for males than females. The results indicated correlations between the heritability of hypomania, environmental factors and bipolar disorder and genetic risk scores for schizophrenia and major depression. The authors suggest that sub-illness hypomania overlaps with all severe mental illnesses and may be a continuous trait for psychiatric disorders when at its extreme.
Bipolar disorder and inflammation
There is significant variation among symptoms and illness presentations among individuals with bipolar disorder. As a result of this variation, treatment options often do not address the full range of symptoms an individual may experience. A new article by researchers from the University of Texas Health Science Center at Houston published in the Journal of Biomedical Sciences last year reviews the evidence surrounding inflammation and bipolar disorder to help explain some of this variation.
Included in this review is how hormones such as cortisol, melatonin, serotonin, dopamine and norepinephrine have roles in both mood regulation and immune signaling. For example, individuals with bipolar disorder have a lower evening peak of melatonin levels, a hormone important for sleep, and more sensitivity to light-induced melatonin suppression compared to individuals without bipolar disorder. Additionally, individuals with bipolar disorder have elevated cortisol levels, a stress hormone, during all disease phases, including when mania or depression symptoms are not prominent.
Overall, the authors point to how “inflammatory signaling draws a common thread between so many of these disparate disease processes,” which presents an opportunity for targeted treatment therapies to individual patients.
The perinatal period and bipolar disorder
The perinatal period, defined as the time a woman is pregnant and just after birth, is an especially vulnerable period for women with bipolar disorder. Published in Current Psychiatry Reports last month, authors from the University of Colorado provided an update on the research and treatment guidelines surrounding the perinatal period and bipolar disorder.
The authors find that manic and depressive episodes that occur postpartum, or after the birth of a baby, are unique compared to mood episodes that occur in a woman’s life outside of the postpartum period. Additionally, women with a previous history of bipolar disorder are at high risk of relapse of psychiatric symptoms during the postpartum period.
Lithium, a common treatment for bipolar disorder, can cause complications to both the mother and child during pregnancy and breastfeeding. The authors write that taking lithium during pregnancy seems safer than originally thought, however more research is needed to fully understand its safety profile in pregnant women with bipolar disorder.
