A third of all Indian women suffer from domestic violence in their lifetime (pdf), and the impact of this physical and mental abuse can be deadlier than previously imagined. A new study has found that domestic abuse of mothers might contribute to the death of young children.

Cultural norms have kept the issue of domestic violence behind closed doors for far too long. There wasn’t much that women could do until 2005 when the Protection of Women from Domestic Violence Act came into action. And though there has been some progress since, India remains a long way from addressing the evils that befall half its population.

In a working paper (pdf), Seetha Menon, a PhD student at the University of Essex, used a large survey to look at the effects of domestic violence. The data came from the 2007 National Family and Health Survey, which interviewed 124,385 women between 16 and 49 years of age.

When she controlled for factors such as household wealth, age, and birth order, she found that nearly one in ten of child deaths under the age of one could be attributed to domestic violence. If the sample was narrowed to only rural households, that number doubled to nearly one in five deaths.

Direct trauma to the foetus while the mother is pregnant is just one of many ways in which domestic violence could lead to child death. The psychological stress can also have a detrimental impact on the development of the child, which can result in low birth weight or preterm delivery, eventually contributing to early death.

Menon’s study, which she will soon be sending for a review, shows that the impact of domestic violence is worse for the girl child. It is not clear why that is the case, because gender determination is illegal in India. But it might go in some way to explain India’s poor sex ratio of 918 women per 1,000 men.

Although urban households seem to fair better with lower levels of domestic violence-related deaths, it might be a result of a bias. “Urban India has been shown to have a higher threshold to privacy, which means women in cities are less likely to report episodes of domestic violence,” Menon told Quartz.

The study also showed that backward castes in India suffered from more domestic violence than other castes, even after controlling for other factors such as wealth.

There are some limitations to the study. For instance, in the health survey, women did not specify the timing of when they suffered domestic violence. And previous research has also shown a connection between domestic violence and child mortality. But Menon argues that her research is the first to show a cause-and-effect relationship (beyond the obvious harm caused by direct physical trauma).

The results add to mounting evidence of the evils of domestic violence. Anything that can be done – through people’s actions in civil rights movements or government’s intervention with gender equality laws – will go a long way to help save lives and make existing ones better.

This article was originally published on qz.com.