Children more likely to have lower IQs if mothers are depressed

Children who grow up with depressed mothers are more likely to have lower IQs, new research suggests. 

Some 10 to 25 percent of women experience postpartum depression, which may delay their baby’s development. 

But new research from the University of California, San Diego suggests that the impact on their their children’s mental development and learning can continue through the child’s teenage years, if the depression does too. 

As rates of depression soar ever-higher in the US, proactively combating and treating even low-grade depression in mothers may help curtail the burden of the mental illness for future generations, the study suggests.   

IQs among the children of mothers with depression were six percent lower than those of other children, extending from infancy to their teenage years 

Around one in 10 women will suffer depression at some point.

Once treated as an isolated and internal mental illness, recent developments in depression research continually uncover its public health implications. 

We have long known that when a mother has postpartum depression, her children are at greater risks of cognitive, speech and developmental delays and even behavioral disorders like attention deficit hyperactivity disorder (ADHD). 

The cause behind this is unclear, however. Some suggests that mothers’ hormonal changes may influence the brain development of their babies to lead this, while others suggest they may be more behavioral. 

As children get older, however, and their mothers’ depression persists, the possible ways that a mother’s depression could slow their learning are more clear. 

Play and interaction are key catalysts for learning and neural connections as children’s brains are developing, and often their mothers are their first and most frequent playmates. 

But one among depression’s hallmark symptoms are a sense of isolation and disinterest in otherwise enjoyable activities. 

So it stands to reason that a mother struggling with depression might be less apt to play with and therefore stimulate her child’s mind.  

To test this theory, researchers surveyed around 900 healthy children and their mothers living in Santiago, Chile, at five-year intervals from the child’s infancy through to the age of 16.

They observed how affectionate and responsive mothers were to their children at each age period, as well as how much mothers provided age-appropriate learning materials.

Children were assessed on verbal cognitive abilities using standardized IQ tests during each assessment. Mothers were tested for symptoms of depression.

Dr Patricia East, a research scientist at University of California San Diego School of Medicine, said: ‘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,’ she said. 

‘The consistency and longevity of these results speak to the enduring effect that depression has on a mother’s parenting and her child’s development,’ Dr East added.

On a scale from one to 19, the average verbal IQ score for all children in the study at age 5 was 7.64.

Children who had severely depressed mothers were found to have an average verbal IQ score of 7.30 compared to a score of 7.78 in children without depressed mothers.

Dr East said: ‘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.’

Throughout the study, at least half of the mothers were determined to be depressed based on a questionnaire with questions such as ‘Are you sad?’ and ‘Do you find yourself crying?’

Dr East said: ‘For mothers in the study, there were many stressors in their lives.

‘Most of the mothers, while literate, had only nine years of education, were not employed outside the home and often lived with extended family in small, crowded homes – factors that likely contributed to their depression.

‘Many mothers suffer from depression in the first six months after childbirth, but for some, depression lingers.’

Dr East said data from the study suggested about one in five mothers who are severely depressed when their child turns one remain depressed for a long time.

She added: ‘For health care providers, the results show that early identification, intervention and treatment of maternal depression are key.

‘Providing resources to depressed mums will help them manage their symptoms in a productive way and ensure their children reach their full potential.’

The findings, published in the journal Child Development, may not be fully scalable to mothers in the US, but they underscore the disproportionate ways that depression may burden not only lower-income, less-educated mothers, but their children as well.