Women who were abused as children are more than twice as likely to get depressed as adults than women who reported no abuse, a new study shows.
Seeing or experiencing violence as a child may cause some kind of brain insult, which changes the brain's chemistry, the researchers suggest.
"We've seen numerous studies in that past that have shown a relationship between childhood violence, both sexual and physical, and adult depression in women," says study author Lauren Wise, who is studying for her doctoral degree at the Harvard School of Public Health.
"We also know there's a higher prevalence of depression in women than in men. But all the prior studies had used predominately clinical samples and were much smaller in size. We wanted to explore violence during childhood as a possible explanation for the increased risk of depression in women," she adds.
According to the National Institute of Mental Health (NIMH), depression strikes women twice as often as it does men, regardless of race or social status. Although no one knows exactly why that is, researchers have focused on explanations involving reproductive, hormonal, genetic or other biological factors, as well as abuse or oppression, relationship issues and certain psychological and personality characteristics.
To examine whether childhood abuse was associated with adult depression, Wise and her colleagues questioned a random sample of 732 women in the Boston area who were between the ages 36 and 45, on whether they had experienced physical or sexual abuse as a child. Then the researchers used a standard measurement to see whether the women had episodes of major depression as adults.
"We defined physical abuse as episodes of being threatened, or actual infliction of physical harm, such as being pushed, grabbed, shoved, kicked, bitten, punched, spanked, choked or burned, or hit with an object," Wise explains. "We grouped fear of abuse and experience of abuse into one category, because women who reported actual experiences of abuse had reported both fear and [actual] experience as a child. We also included instances of, or fear of, sexual abuse."
Out of all the women, 363 said they were either physically or sexually abused as children or adolescents, Wise says. Women who reported any type of childhood abuse were 2.5 times more likely to have an episode of major depression than those who reported no abuse. Women who reported both physical and sexual abuse as children were more than three times as likely to suffer depression.
The findings were published in a recent issue of The Lancet.
"What we did was verify with our study those earlier studies that showed a relationship between sexual and physical violence in childhood and adult-onset depression," Wise says. "And while this study does provide some evidence that violence during childhood is a possible explanation for the increased rate of depression in women, only studies that look at violence in both men and women could better address the question."
"We think there might be a biological mechanism," Wise adds. Previous animal and human studies have shown some evidence that severe life stresses can cause long-term chemical problems in the brain, she says.
The study should be a wake-up call to doctors, Wise says. "We underscore the importance of encouraging healthcare providers to routinely screen women for a history of violence. Screening women could be a way of being prepared, of asking the right questions, as a signpost to look for the symptoms of depression."
The findings are not at all surprising, says Laurie Young, a senior vice president for the National Mental Health Association.
"What everyone has to remember, what women have to remember, is that all depression is treatable," she says. "What we know and what there is every indication of is that the experience of trauma can alter brain chemistry. So, with the use of antidepressants in combination with psychotherapy, treatment can be very successful."
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Abuse linked to depression