Having a depressed mother during elementary or middle school raises the likelihood a child will engage in risky behaviours like drinking and smoking during the teen years, according to a new Canadian study.
Depression in the child
Based on nearly 3,000 children followed since they were toddlers, the researchers also found that kids with depressed mothers in "middle childhood" were likely to start risky health behaviours earlier in their adolescence than other kids.
"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 behaviour," Ian Colman, the study's senior author, told Reuters Health in an email.
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"Given how prevalent maternal depression is, and that risky adolescent behaviours are associated with poor long-term outcomes in adulthood, we thought better evidence in this area could be really useful" said Colman, a researcher at the University of Ottowa in Ontario.
Previous studies have suggested a link between a mother's depression during pregnancy or right after a baby is born to the teenager's mental health.
But not much is known about maternal depression and later adolescent behaviours, Colman's team writes in the journal Paediatrics.
Engagement in risky behaviours
The study team analysed data from the National Longitudinal Survey of Children and Youth, a large Canadian population study that began when the kids were ages two to five in 1994 and ended in 2009 when they were teenagers.
Every two years, the participating mothers answered questions about their own physical and mental health, and about the health of their kids and spouses or partners, their available social support and family functioning.
Once the children reached the age of 10 or 11, they filled out their own questionnaires.
When they reached adolescence, the young participants were asked about their engagement in risky behaviours such as drug and alcohol use, carrying a weapon or running away from home. A total of 2,910 teens completed the study.
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The researchers found that teens who had been exposed to maternal depressive symptoms during middle childhood were more likely to use alcohol, cigarettes or marijuana, and to engage in violent and nonviolent delinquent behaviour.
In addition, they were more likely to engage in these behaviours earlier than teens whose mothers had low or no symptoms of depression.
Negative parenting behaviours
The study team also found that teens exposed to recurrent maternal depression throughout their childhood engaged in more nonviolent risky behaviours compared to those whose mothers had low or no depression.
In contrast, kids whose mothers' depression symptoms started when the child was already in the early teens did not engage in more risky behaviours than kids without any maternal depression exposure.
The results don't prove that the mothers' symptoms when their children were young caused the children's behaviour in adolescence.
But, the authors write, 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 behaviours may harm the child's own development during this sensitive time and lead to "lasting deficits", they speculate.
Colman said that asking for help can be hard, but even just talking about how she is feeling can sometimes be a really helpful start on the road to recovery for a mother experiencing depression.
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."