New research into stress in early life has revealed that it can permanently alter specific genes. The work, published in the journal Nature Neuroscience, shows that trauma or stress endured in infancy can cause behavioural changes in later life that may lead to psychological disorders, such as depression.
Links between childhood trauma or neglect and psychiatric disorders in adulthood have been widely acknowledged in the past; this work provides the first evidence that the effects may not be totally psychological. Epigenetic changes - permanent alterations to the genome caused by non-genetic factors - were also previously known to create changes in the expression of genes.
The group of researchers was led by Christopher Murgatroyd at the Max Planck Institute of Psychiatry in Munich, Germany. The scientists investigated the effects of putting mouse pups in stressful situations, simulated by separating the mice from their mothers for three hours per day for the first ten days of their lives. This was already known to cause changes to the hormone levels and stress factors in mice, which persist in later life, but this study went into 'molecular detail' of how stress could 'programme' long-term behaviour, Murgatroyd told BBC News.
The scientists found that the early-life stress in the mice caused a surge in stress-associated hormones. This increased the expression of a regulator of the aginine vasopressin (AVP) gene, which is a regulatory hormone linked to mood and cognitive behaviours. The increase in AVP expression was persistent in the mice, and resulted in changes in their behaviour such as memory loss and reduced ability to cope with stress.
The group were then able to reverse the effects seen in the stressed mice by using a chemical compound to block the receptor of the AVP hormone. The results were only partially reversed, however, most likely because there are other genes, regulators, or hormones at work in this process that were not analysed in this study.
The study is the first to identify epigenetic changes induced by stress, describe the behavioural features caused by these changes and link these to key features of disorders like depression. Professor Hans Reul, a neuroscientist at the University of Bristol, UK, said in an interview with the BBC that the work is 'a very valuable addition to the body of work on the long-term effects of early-life stress. There is strong evidence that adversities such as abuse and neglect during infancy contribute to the development of psychiatric diseases such as depression. This underscores the importance of the study of epigenetic mechanisms in stress-related disorders'.