Scientists from France and Germany have found that childhood trauma leaves a noticeable mark on the brain structure of healthy adults, but in people with alcohol dependence these specific changes are not visible. The study was published in the journal Addiction Neuroscience.
The work involved 84 people with alcohol dependence of varying severity (many were undergoing treatment in clinics) and 83 adults without alcohol problems. All completed questionnaires about childhood trauma - emotional, physical or sexual abuse, as well as emotional and physical neglect. Then, using magnetic resonance imaging (MRI - a method that allows three-dimensional images of the brain to be obtained), the scientists measured gray matter volume, cortical thickness and the degree of gyrification (folding) in four brain regions associated with emotions, stress and self-control.
As expected, in people with alcohol dependence gray matter volume was reduced in all the studied areas compared with healthy participants. This is consistent with previous data that chronic heavy drinking physically shrinks brain tissue.
However, the main finding concerns the link between childhood trauma and brain structure. In healthy adults who reported a higher level of trauma in childhood, there was a smaller gray matter volume in the right part of the inferior frontal gyrus - an area that helps restrain impulses and manage emotions. At the same time, on the left side of the same gyrus they had increased cortical folding. This may be a compensatory reaction: the brains of people who did not become dependent adapt to early stress by changing gyrification in order to preserve self-control functions.
In participants with alcohol dependence, no such link was found between childhood trauma and brain volume or folding. The researchers suggest that severe tissue loss due to years of heavy drinking may mask or override the subtler traces of childhood trauma.
To test this, the scientists conducted an additional analysis only in the group of dependent people. They statistically accounted for the severity of each patient's current alcohol consumption. And then the picture changed: a higher level of childhood trauma turned out to be associated with lower cortical thickness in the left inferior frontal gyrus. It appears the traces of trauma do not disappear, but hide beneath the coarser damage from alcohol.
It is important to emphasize: the study is cross-sectional, it cannot prove a cause-and-effect relationship. Only a statistical association (correlation) has been established between reports of trauma and brain measurements - by itself it does not mean that trauma caused the changes. In addition, the data on childhood trauma are based on participants' memories, and memory becomes distorted over time. The analysis of cortical thickness in the dependent group was additional and was conducted on a slightly smaller sample, since not all patients fully completed the questionnaires about recent alcohol consumption.
The authors conclude: to untangle the influence of early trauma and later dependence, long-term studies are needed that follow people from childhood and measure the brain before drinking begins and as it develops.