A study published in European Neuropsychopharmacology showed that young adults who experienced childhood maltreatment have various structural brain features. They depend on age, sex and the specific type of trauma experienced. The work was led by Fabian Hut of the Carl Gustav Carus University Hospital at the Technical University of Dresden and David Popovic of the Institute of Psychiatry of the Max Planck Society and Ludwig Maximilian University of Munich.
The study involved 251 people aged 17 to 35 (average about 25 years) who sought help due to early symptoms of mental disorders. Among them were 130 men and 121 women. All of them completed the Childhood Trauma Questionnaire, underwent structural MRI (magnetic resonance imaging) of the brain and took tests for symptoms of depression and level of functioning.
The scientists used a machine learning algorithm to identify links between individual questionnaire items, age, sex and 182 measures of brain structure. This approach made it possible not to average traumatic experience but to take each type of abuse into account separately.
The first identified profile was associated with older age, severe physical abuse and a tendency to deny experienced difficulties. In such participants, the cerebral cortex - its folded outer layer, responsible for complex thinking and processing signals from the sense organs - was thinner. This profile explained 18% of the total variation between the questionnaire data and the brain measurements. Moreover, cortical thickness made the main contribution (over 86%), while surface area and the volume of deep structures made a minimal one. Importantly, this concerns differences between people at a single point in time, not tissue loss over the years.
The second profile turned out to be specific to women and explained 32% of the variation. It linked female sex (the most weighty factor) and a high level of emotional abuse with a reduction in the volume of the left amygdala - an almond-shaped cluster of neurons deep in the temporal lobes that is involved in recognizing threats and regulating emotions. The reduction affected the total volume of the left amygdala and three of its internal divisions: the basal, paralaminar and accessory basal nuclei. No such link was found in men.
In addition, women with high scores for emotional abuse coped worse with everyday tasks one and two years after the start of the study. The average functioning score among all women with follow-up data rose from 62.6 to 69.6 after one year and to 72.0 after two years, but those who suffered more from emotional abuse had lower indicators. This link persisted after two years as well, with adjustment for the baseline level of functioning.
The authors emphasize: the study does not prove that abuse causes brain changes. Scanning was performed once, so it cannot be ruled out that the structural features existed before the trauma or became a consequence of an incipient disorder. In addition, the childhood data are based on participants' memories, which may be inaccurate. The direct statistical link between emotional abuse and left amygdala volume turned out to be non-significant, and sex was the strongest predictor of amygdala size. The scientists acknowledge that the identified patterns require confirmation in larger independent samples.
Independent expert Zzai-Fu Yao of National Tsing Hua University in Taiwan noted that the work is a promising exploratory study, but interpretation of the results should remain cautious. "People should not have to demonstrate an abnormal brain scan for their suffering to be taken seriously," he emphasized.