Adults who were victims of child abuse tend to have thinner layers of myelin coating in the brain, according to a new study by McGill University in Canada.
Myelin is the protective fatty coating that covers the long thread-like parts of nerve cells called axons and helps them conduct electrical signals more efficiently. Myelin builds up progressively (in a process known as myelination) primarily during childhood, and then continues to mature until early adulthood.
Earlier research has shown significant white matter abnormalities in the brains of people who had experienced child abuse. (White matter is mostly made up of billions of myelinated nerve fibers stacked together.)
However, because these observations were made in the brains of living people through MRI (magnetic resonance imaging), it was impossible to gain a clear picture of the affected white matter cells and molecules.
To better study the microscopic changes which occur in the brains of adults who have experienced child abuse, the researchers compared post-mortem brain samples from three different groups of adults: people who had committed suicide who suffered from depression and had a history of severe childhood abuse (27 individuals); people with depression who had committed suicide but who had no history of being abused as children (25 individuals); and brain tissue from a third group of people who had neither psychiatric illnesses nor a history of child abuse (26 people).
The findings reveal that the thickness of the myelin coating in a significant proportion of the nerve fibers was reduced only in the brains of those who had suffered abuse as children. The researchers also found underlying molecular changes that selectively affect the cells responsible for myelin generation and maintenance. In addition, increases were found in the diameters of some of the largest axons among only this group.
The researchers speculate that together, these changes may alter functional coupling between the cingulate cortex and subcortical structures such as the amygdala and nucleus accumbens (areas of the brain linked respectively to emotional regulation and to reward and satisfaction). These changes may also contribute to altered emotional processing in adult victims of child abuse.
The researchers conclude that early life abuse may result in long-term disruption of a range of neural functions in the anterior cingulate cortex. They are planning to conduct more research that will help determine exactly how these effects impact the regulation of emotions and attachment.
Severe childhood abuse is tied to an increased risk of psychiatric disorders such as depression, as well as high levels of impulsivity, aggressivity, anxiety, more frequent substance abuse, and suicide.
Source: McGill University