A neuroimaging study conducted in Italy found that bipolar disorder patients who reported more adverse childhood experiences tended to have worse brain white matter integrity. This association was also present in depressed patients, but the effect was less pronounced and structurally different. This research european neuropsychopharmacology.
Adverse childhood experiences (ACEs) are potentially traumatic events that occur during childhood that can impact a child’s physical, emotional, and psychological development. This concept was popularized by the Childhood Adversity Experience Study, which investigated how stress in childhood is related to later health outcomes.
ACEs typically include experiences such as physical abuse, emotional abuse, sexual abuse, neglect, and exposure to domestic violence. It may also involve family dysfunction, such as living with a family member who has substance abuse problems or mental illness, or who is incarcerated.
These experiences can disrupt a child’s sense of safety and stability, leading to chronic stress during a critical period of development. Prolonged exposure to stress during childhood can affect brain development and the body’s stress control systems. Research shows that people with a high number of ACEs are at higher risk for mental health problems such as depression, anxiety, and substance use disorders.
ACEs are also associated with an increased risk of chronic physical health conditions such as cardiovascular disease and diabetes. However, the presence of supportive relationships and a protective environment can buffer the negative effects of adverse experiences.
Study author Marco Paolini and his colleagues note that previous research has shown that adverse childhood experiences can negatively impact the integrity of the brain’s white matter. However, these effects are not universal and appear to be rather dependent on a person’s mental health diagnosis. They believed that these experiences had a clear effect on people with bipolar disorder, but less so on people with major depressive disorder.
These researchers conducted their study based on the hypothesis that the effects of adverse childhood experiences on the microstructural integrity of the brain’s white matter would be different in people with bipolar disorder and people with major depressive disorder.
Brain white matter integrity refers to the structural quality and organization of the brain’s white matter tracts. The white matter of the brain is made up of bundles of myelinated nerve fibers that connect different brain regions and allow communication between them.
Myelin is a substance that insulates nerve fibers, allowing nerve impulses to travel faster and creating a white appearance. Generally, higher white matter integrity indicates more efficient neural connections and information transmission in the brain, but decreased integrity may reflect developmental abnormalities, aging, injury, or neurological or psychiatric disorders.
Study participants were 260 inpatients admitted to the psychiatric ward of San Raffaele Hospital during an ongoing depressive episode. Of these, 140 were diagnosed with major depressive disorder and 120 with bipolar disorder. Patients’ ages ranged from 21 to 69 years.
Patients underwent magnetic resonance imaging scans of brain structures. A subsample of 162 patients provided blood samples, allowing researchers to perform genotyping and calculate a polygenic risk score (PRS), which individually estimates a person’s genetic risk of developing major depressive disorder or bipolar disorder. Participants also completed an assessment of adverse childhood experiences (28-item Childhood Trauma Questionnaire), including family environmental adversity (At-Risk Families Questionnaire).
The results showed that patients with bipolar disorder who reported more adverse childhood experiences, particularly physical abuse, emotional abuse, and physical neglect, tended to have widespread deterioration in white matter health. The situation was different in patients with major depressive disorder, where the association was less pronounced and affected different structural indicators of white matter.
Further analysis revealed that the strength of the association between adverse childhood experiences and white matter integrity in the brain depended on a person’s genetic risk for bipolar disorder. Importantly, this genetic regulation was specifically present in patients with major depressive disorder, but not in patients with bipolar disorder. In patients with bipolar disorder, childhood trauma negatively affects white matter, regardless of genetic risk score.
However, in patients with depression, those at high genetic risk for bipolar disorder had white matter changes that were similar to those in patients with bipolar disorder. Conversely, depressed patients with a low genetic risk for bipolar disorder had the opposite biological response to trauma. These findings suggest that major depression is a highly heterogeneous diagnosis and that some depressed patients actually have a bipolar disorder-like biological response to trauma.
“In this study, we identified differences in the effects of childhood maltreatment on WM (white matter) microstructure among patients suffering from major depression or bipolar disorder, and the deleterious effects were more pronounced in BD (bipolar disorder) compared to MDD (major depressive disorder). This may indicate different pathophysiological pathways by which childhood maltreatment, a common environmental risk factor, influences the development of the two diseases,” the study authors concluded. They added that their findings “give credence to the concept of a common disease biology with bipolar disorder in some MDD patients and perhaps provide future tools to disentangle the heterogeneity of MDD.”
This study contributes to scientific understanding of the neural basis of mental health disorders. However, it should be noted that the study design does not allow definitive causal inferences to be drawn from the results. Furthermore, information on adverse childhood experiences was based on childhood recollections, leaving room for recall bias to influence the results.
The paper, “Different effects of adverse childhood experiences on white matter microstructure in major depression and bipolar disorder: The moderating role of genetic liability,” was written by Marco Paolini, Laura Refaeli, Valentina Bettnagli, and Cristina Written by Lorenzi, Sara Spadini, Beatriz Blavi, Lidia Fortaner-Uya, Giulia Gulino, Chiara Fabbri, Alessandro Ceretti, Raffaella Zanardi, and Cristina. Colombo, Francesco Benedetti, Sara Poletti.
