New study also finds that such individuals are significantly less likely to respond to psychological or drug-based treatments

People with a history of abuse or maltreatment during childhood are twice as likely to have recurrent episodes of depression in adulthood, according to scientists. These individuals are also less likely to respond well to psychological or drug-based treatments.

Researchers at the Institute of Psychiatry (IoP) at King's College London pooled information from 26 studies that included data from more than 26,000 people. "What we have observed is that childhood maltreatment predicts recurrence, the persistence of the episodes and response to treatment," said Andrea Danese, a clinical lecturer in child and adolescent psychiatry at the IoP, who led the work.

Depression affects one in 10 people in the UK and is a major cause of disability and mortality. According to the World Health Organisation, depression will become the second most prominent contributor to the health burden across all ages by 2020.

In their meta-analysis, the researchers examined data from 16 epidemiological studies involving more than 23,000 people and 10 clinical trials involving more than 3,000 people.

Rudolf Uher of the IoP, who co-authored the study, said the researchers used five indicators of maltreatment in analysing the work: rejecting interaction from a mother; harsh discipline reported by a parent; unstable primary caregiver arrangement throughout childhood; and self-reports of harsh physical or sexual maltreatment.

If a person only had history of one of these indicators, they were classed as probable in terms of maltreatment. If a participant had two indicators, they were classed as definitely maltreated.

The results of the study, published on Monday in the American Journal of Psychiatry, showed that someone with one or more indicators of childhood maltreatment had a chance of developing recurrent depression in later life around 2.27 times higher than that of people who had no history of maltreatment. They were also 43% more likely to experience a poor outcome when it came to psychological or drug-based treatment.

"If these things happen early in life, they seem to be much more powerful," said Uher. "People who grow up in poor conditions, they often end up marrying someone who doesn't treat them that well and they have more stresses. When we look at whether maltreatment causes depression, we have all these things in between that explain most of the relationship."

In addition, he added, being treated badly as a child might also have meant poor performance at school, leading to less likelihood of getting a good job and other associated problems.

Previous research has shown biological changes in children who are treated badly because of the stress placed on their bodies, including the brain, the hormonal and immune systems.

"There are a number of research papers showing that, for example, maltreated children have, already in childhood, abnormalities in the pre-frontal cortex that may have an impact on their neuropsychological function, especially executive function, things like sustained attention or regulating emotions," said Danese. These biological differences might explain some of the observed increase in recurrent depression, he said, but that link would have to be established in further research.

Uher said that the findings could help in the care of people with mental illness. "Whilst we still do not know exactly what type of treatment may improve the care of maltreated individuals, it may be that new treatments based on the biological vulnerabilities associated with childhood maltreatment could prove an exciting avenue for research."