Parents suffering from depression should get the necessary help if they want to protect their kids. A new study shows that children are likely to receive lower grades in school if at least one parent suffers from depression.

Findings of the study, which was published in JAMA Psychiatry on Feb. 3, provide another evidence of how parental depression can negatively affect children.

Earlier studies have already found that children with depressed parents are likely to suffer from brain development problems. They are also at increased risk of having behavioral, emotional and psychiatric problems.

Brian Lee and colleagues from Drexel University's Dornsife School of Public Health followed more than 1.1 million children in Sweden who were born between 1984 and 1994. By comparing the final grades of the children at age 16, the researchers found that the kids' school performance suffered when their parents were diagnosed with depression.

"Depression is a social disease," Lee says. "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."

Maternal and paternal depression impacted the performance of the children in their final year in school even when the depression occurred years earlier. The researchers also observed that depression in mothers had more impact on daughters than sons. The condition also affects learning regardless if it is the mother or the father who is depressed.

The researchers say their study has only provided an association between parental depression and poor academic performance, but they have offered explanations for their findings.

One is that depression can run in the family. Lee says that since depression can be handed down, it is possible that the kids do not perform well in school because they have undiagnosed mood disorders.

Babies whose mothers are depressed also receive poorer care such as less nurturing or less breast-feeding, which could have long-term effects on the children's ability to learn and solve problems. Childrearing is already demanding in itself and this becomes more difficult if a parent suffers from depression.

Myrna Weissman, from the New York State Psychiatric Institute, says that treating mothers for depression with medication or psychotherapy has proved helpful in reducing problems in children.

"Therefore you should be treating the parents," says Weissman. "Sometimes you have to treat the children, but you should start with the parents."