A longitudinal neuroimaging study comparing patients with bipolar disorder and healthy controls found that bipolar patients with more frequent depressive episodes tended to have increased gray matter volume in the right lateral cerebellum. The paper was published in a magazine neuropsychopharmacology.
Bipolar disorder is a mental health condition characterized by extreme changes in mood, energy, and activity levels. People with bipolar disorder experience manic or hypomanic episodes with elevated mood or irritability, increased energy, and decreased need for sleep. These episodes alternate with depressive episodes characterized by sadness, loss of interest, fatigue, and feelings of hopelessness.
Research suggests that differences in brain structure, neurotransmitter systems, and emotion regulation networks may play a role in the development of bipolar disorder. The disorder usually begins in late adolescence or early adulthood, but can appear early or late in life.
Study author Florian Thomas-Odenthal and colleagues wanted to examine changes in gray matter volume in the brains of bipolar patients with and without recurrent depressive or manic episodes during a two-year follow-up and compare them to healthy participants.
The authors hypothesized that patients with bipolar disorder who experienced a new depressive or manic episode during the follow-up period would show decreased gray matter volume associated with manic episodes and increased gray matter volume associated with depressive episodes. Gray matter is a part of the central nervous system that primarily consists of nerve cell bodies, dendrites, and synapses.
Study participants were 124 individuals participating in the ongoing Marburg-Münster Affective Disorders Cohort Study (MACS), which studies the neurobiology of major psychiatric disorders. Sixty-two of the participants had bipolar disorder, while the remaining 62 were healthy and were included as control participants.
All participants completed magnetic resonance imaging at two time points approximately 2 years apart (mean 2.18 years). Separately, study participants completed semi-structured clinical interviews at these two time points, reporting on their disease course, whether they were currently experiencing symptoms of the disorder (remission status), and current drug use.
They also completed assessments of psychopathology, global psychosocial functioning, and familial risk. Their BMI was calculated. The study authors also divided participants with bipolar disorder into those who experienced new episodes of mania or depression during the follow-up period and those who did not.
The results showed that bipolar disorder patients who did not experience new manic or depressive episodes during the follow-up period tended to show a significant decrease in gray matter volume in the right lateral cerebellum. Bipolar disorder patients who experienced a depressive or manic episode during follow-up showed a non-significant increase in gray matter volume. Gray matter volume in this region did not change in healthy participants.
More nonmanic depressive episodes during follow-up were moderately associated with increased gray matter volume in the aforementioned brain regions. In patients with bipolar disorder who did not experience new manic or depressive episodes during follow-up, longer duration of manic episodes before baseline assessment was associated with decreased right lateral cerebellar gray matter volume during follow-up.
“Our findings highlight the dynamic nature of brain changes in BD (bipolar disorder). Increased GMV (gray matter volume) in BD patients with relapses may be due to acute neuroinflammatory mechanisms, including glial cell proliferation, whereas decreased GMV in BD patients without relapses may result from aberrant synaptic miniaturization or pruning as a result of past neuroinflammation during BD episodes,” the study authors concluded.
This study sheds light on structural changes in the brain associated with bipolar disorder. However, note that the study design does not allow definitive causal inferences to be drawn from the results.
The paper, “Differential effects of manic and depressive episode recurrence on longitudinal gray matter volume changes in bipolar disorder,” was authored by Florian Thomas-Odenthal, Lea Teutenberg, Frederike Stein, Nina Alexander, Linda M. Bonnekoh, Katharina Brosch, Kira Flinkenflugel, Janik Goltermann, Dominik Grotegerd, Tim Hahn, Andreas Jansen, and Elisabeth. J. Lehr, Susanne Meinert, Julia Katharina Pfahr, Harald Lenz, Kai Ringwald, Navid Schulmeier, Thomas Stief, Benjamin Straube, Katharina Thiel, Paula Useman, Axel Krück, Igor Nenadić, Udo Danrowski, Thilo Kircher.
