February 04, 2016
A Drexel University-led international study of more than 1 million children has found that teens' academic performance can be impacted if their parents ever had depression, even if they were diagnosed before the child was born.
"I think it's often not realized that mental health issues affect persons beyond [the] immediate patient," said Dr. Brian Lee, an associate professor of epidemiology and biostatistics at Drexel's School of Public Health. "Persons in the family, especially children, who are going to be more vulnerable, are likely to be at risk as well."
Researchers had access to an enormous data set encompassing more than 1 million children born in Sweden between 1984 and 1994 as well as their parents' mental health records. Sweden was chosen because it has a universal health care system and keeps meticulous records that are available in anonymized form to health researchers.
"It would be impossible to do a similar study like this in the U.S. without millions of dollars being invested," Lee noted.
Scientists at Drexel; the Karolinska Institutet in Stockholm, Sweden; and the University of Bristol in England had access to a register of year-end grades for the nation's 16-year-olds, plus records of whether their parents had been diagnosed with depression. Adopted children were not included in the study, since depression is inheritable.
Parental depression was found to have an even greater effect on grades than coming from a low-income family. Moreover, no matter how old the children were when their parents were diagnosed, it affected their grades at age 16.
"One of the interesting things that we did observe was that even if parental depression occurred before the child was born, that was still associated with school performance when the child was 16," said Lee.
However, these correlations were not always large enough to be statistically significant.
"In general, paternal depression and maternal depression in all periods were independently associated with worse school performance, although paternal depression during the postnatal period did not attain statistical significance," researchers wrote in the study, which was published in the journal JAMA Psychiatry.
In particular, researchers saw greater effects when the mother was depressed than when the father was depressed, especially if they had a daughter. For example, a girl's final grades were typically 5.1 points lower on a 1-100 scale if her mother had ever been depressed, while a boy's final grades were 3.4 points lower.
"Maternal depression in the mother seemed to affect girls more than it did boys, in terms of their school performance, whereas for a father's depression, it had an equivalent effect in both girls and boys," said Lee.
That finding suggests that the mother-daughter relationship is particularly meaningful to a child's development, or that girls more keenly feel the burden of having a parent with mental illness.
Lee said that the findings fit well with previous research. The large sample size, plus the fact that researchers saw associations between depression and grades no matter when parents were diagnosed, gives very strong evidence to a theory that rings true: "Parental depression affects the child."