Stress in early years could alter children's DNA

Children who have been physically abused or bullied are more likely to have shorter telomeres. These structures, found at the ends of chromosomes, act like the plastic caps on shoelaces, and prevent DNA strands from unravelling.

Previous research has shown that degradation of telomeres may be exacerbated by stress and has been linked with ageing and diseases such as diabetes and dementia.

Professor Avshalom Caspi, the study's co-author, says: 'Children who experience physical violence appear to be ageing at a faster rate'. As a result, he says, they may face increased risk of disease in adulthood and possibly a shortened lifespan.

Researchers at Duke University in Durham, North Carolina, used data from the Environmental Risk Longitudinal Twin study, which followed 1,100 twins born in the UK from birth to 18 years old. They interviewed mothers about their children's exposure to violence, including physical abuse, bullying and exposure to maternal domestic violence.

Half of the 236 children selected for the study had experienced at least one form of violence. The team measured the length of their telomeres using DNA samples collected when the children were five and ten years old.

The study, published in Molecular Psychiatry, not only found a relationship between violence and shortened telomeres, it also showed that the magnitude of telomere loss depended on the number of violent experiences.

Those who experienced violence between the ages of five and ten showed a clear pattern of telomere loss. In contrast, those who had experienced violence before the age five but not after showed signs of telomere growth. While lead author Dr Idan Shalev concedes these findings could be the result of errors in telomere measurement, other studies have suggested a reduction in stress can lead to a reduction in telomere shrinkage. He says the findings 'suggest new urgency for preventing harm to children' and proposes that improving a child's household environment may protect telomeres.

However, it is still unclear whether telomere shrinkage can be reversed. Professor Charles Nelson, paediatric neuroscientist at Harvard Medical School, says: 'It will be interesting to see if this process will reverse itself if these children are removed from their abusive homes and placed with safe families'.

The researchers plan to measure the telomeres of the participants, who are now 18 years old, again. They hope this will establish whether the shrinkage rate has been slowed, or perhaps even reversed, for children who were removed from violent environments.