Mothers who are suffering from depression could be affecting the development of their child's IQ, according to a new study.

Researchers from the University of California, San Diego have found that mothers who are struggling with depression are less likely to play with their child, thereby affecting their mental development.

The findings, published in the journal Child Development, revealed that children with depressed mothers score lower on cognitive function tests from age 1 through 16.

"We found that mothers who were highly depressed didn't invest emotionally or in providing learning materials to support their child, such as toys and books, as much as mothers who were not depressed. This, in turn, impacted the child's IQ at ages one, five, 10 and 16," said Dr. Patricia East, a research scientist at University of California San Diego School of Medicine, as reported by the Daily Mail.

The researchers surveyed 875 children and mothers living in Chile at five-year intervals for a period of 16 years.

During each visit, the mothers were screened for signs of depression, while the children were tested on verbal cognitive abilities. The researchers also asked questions about the mother's level of engagement with the child at home.

The findings indicated that all the children in the study had an average verbal IQ score of 7.64 at age 5. Those with depressed mothers, however, scored 7.30, compared to 7.78 among children whose mothers did not suffer from depression.

"Although seemingly small, differences in IQ from 7.78 to 7.30 are highly meaningful in terms of children's verbal skills and vocabulary. Our study results show the long term consequences that a child can experience due to chronic maternal depression," East said, according to the Daily Mail.

East noted that most of the mothers who participated in their study only had nine years of education, never had a job outside of their homes and often lived with extended family in a crowded space. She believes that these circumstances likely contributed to their depression.

While some mothers go through depression in the first six months after giving birth, others suffer for much longer, East said.

The researchers said that the findings may not be fully scalable to mothers in the U.S., but highlight how depression affects not only low-income, less-educated mothers, as well as their children.