According to a new Canadian study, having a depressed mother during elementary or middle school increases the likelihood that a child will engage in risky behaviors like drinking and smoking during the teen years.

The study, which followed nearly 3,000 children since their formative toddler years, demonstrated that not only were children with depressed mothers likely to engage in risky behavior, but also were more likely to start risky health behaviors earlier in their adolescence that other children.

"Although there is a fairly good body of evidence suggesting that maternal depression is associated with depression in the child, there is a lot less about how maternal depression might influence adolescent behavior," lead author of the study, Ian Colman says. "Given how prevalent maternal depression is, and that risky adolescent behaviors are associated with poor long-term outcomes in adulthood, we thought better evidence in this area could be really useful."

Previous studies have highlighted the link between a mother's depression during pregnancy and right after a baby is born to a teenager's mental health, but not much is known about maternal depression and later adolescent behaviors. Every two years participants answered questions about their own physical and mental health and the health of their kids, spouses or partners, their social support and family function.  Once the children reached age 10 or 11, they filled out their questionnaires themselves. 

When they reached adolescence, the participants were asked about their engagement in risky behaviors such as drug and alcohol use, carrying a weapon or running away from home. What researchers discovered was that teens who had been exposed to maternal depressive symptoms during middle childhood were more likely to use alcohol, cigarettes or marijuana--and were even more likely to engage in violent and nonviolent delinquent behavior.

In contrast, kids whose mothers' depression symptoms when the child was already in their early teens did not engage in more risky behaviors than kids without exposure to these symptoms.

But, the authors say that middle childhood is a period of increasing cognitive, social and emotional development. Kids in this age group begin school, refine their language skills and increasingly engage in social peer relationships. Being exposed to a mother's depressive symptoms and negative parenting behaviors may harm the child's own development during this sensitive time and lead to "lasting deficits," they speculate.

Colman thinks it's great that there seems to be a growing focus on maternal health, but added, "let's not forget that what is good for mothers is often good for their kids as well."

Asking for help can be difficult for anyone and especially for mothers.  But just talking about how she is feeling can be a helpful start toward recovery.