WEDNESDAY, Feb. 3, 2016 (HealthDay News) -- A child's grades in school might suffer if a parent is suffering from depression, according to a new study.
Researchers found that Swedish teens received lower grades during their final year in school if either of their parents had previously been diagnosed with depression.
The difference in grades was noticeable but not huge, said senior author Brian Lee, an associate professor of epidemiology and biostatistics at Drexel University's Dornsife School of Public Health in Philadelphia.
"It's not an entire letter grade drop, but at the same time it might be the difference between a student passing or failing," Lee said.
Parents' depression could affect the children's home lives, causing stress that impacts their academic performance, Lee said.
"Depression is a social disease," he said. "It doesn't just affect you. It affects your relationships as well. If there's strain there, it may affect the child's academic performance."
Since depression can be handed down, it also could be that the children are not doing as well in school because they suffer from undiagnosed mood disorders, he added.
Infants also might receive poorer care during early development if their mothers are depressed -- less breast-feeding or nurturing, for example -- which could have long-term impacts on children's ability to learn and problem-solve, he said.
"There are many different mechanisms to explain what we've found, and those are just a few possibilities," Lee said.
The study, published online Feb. 3 in JAMA Psychiatry, only found an association between parental depression and worse grades, however, not a direct cause-and-effect relationship.
In the study, Lee and his colleagues examined data on more than 1.1 million children born in Sweden between 1984 and 1994.
Compulsory education ends at age 16 in Sweden, and kids leaving school are assigned a final school grade based on how well they did in their last year. The researchers compared the final grades of teens whose mothers and fathers had been diagnosed with depression against those of teens whose parents do not have a mood disorder.
They found that maternal and paternal depression affected a teen's performance during that final year in school, even if the depression occurred years earlier.
In general, both maternal and paternal depression in any period of a child's life were associated with worse school performance. Maternal depression was associated with a larger negative effect on school performance for girls compared with boys, according to the results.
The impact of depression is as large as similar effects on grades caused by differences in family income and the level of mom's education, the researchers reported.
Dr. Andrew Adesman, chief of developmental and behavioral pediatrics at Cohen Children's Medical Center in New Hyde Park, N.Y., said, "This study provides strong evidence to suggest that children who have a depressed parent are at increased risk for lower academic performance."
Adesman, who was not involved with the research, found it "striking" that parental depression affects learning "regardless of whether the parental depression occurred early in a child's life or later and regardless of whether it is the mother who is depressed or the father."
The findings show that parents suffering from depression need to get help if they want to protect their kids, said Myrna Weissman, chief of epidemiology at the New York State Psychiatric Institute and a professor at Columbia University in New York City.
"We must make sure there's good available treatment for the parent so they stay asymptomatic. That would help a great deal," said Weissman, who wrote an editorial accompanying the study. "We have great data now showing if you treat the parent, the children function better."
Friends of a parent with depression should urge them to seek help, Weissman said.
Schools can offer programs to help children of depressed parents, but Weissman thinks it would be better to get treatment for the adult.
"Depression is highly treatable," she said. "I would certainly begin there."
For more on depression, visit the U.S. National Institute of Mental Health.