By Nestor Lopez-Duran PhD
Historically, most academic and philosophical thinking about depression has been focused on sadness. For example, most interventions for depression attempt to reduce the thoughts and behaviors that make us sad. Likewise, many researchers are interested in examining the factors that make people feel sad or dysphoric. Yet, research studies from many laboratories, including my own research, are reaching the same conclusion: when it comes to depression, lack of happiness may be even more important than too much sadness. Take a look for example the article I discussed last week showing that low levels parental happiness predicted teen depression, but high levels of parental sadness did not.
Today I want to tell you about a study we recently published with my colleagues at the University of Pittsburgh (Dr. Tom Olino is the lead author of this study). In the study, we examined the development of positive affect (e.g., happiness) and negative affect (e.g., sadness) in 200+ children at familial risk of depression and their low-risk peers. These children are at familial risk for depression because at least one of their parents has a history of depression. We consider such children at high-risk because statistically they are significantly more likely than their peers to develop depression. In fact, about 40-50% of children whose parents have a history of clinical depression will develop depression by the end of their teen years.
So given that many of these high-risk kids will develop depression, studying how they differ from their low-risk peers may help us understand what factors contribute to the development of depression. For example, we may find that these kids have a particular gene variation that their low-risk peers do not have, so we can speculate that such gene variation may be involved in the development of depression.
But in our study we were not looking at genes, but instead we wanted to see the natural developmental trajectory of positive and negative affect during early and middle childhood. That is, we wanted to examine changes in positive and negative affect across childhood. We know for example that positive affect increases from infancy into early adolescence. In contrast, negative affect decreases from infancy into early adolescence. This may sound familiar to most parents. Think about the frequency of crying that you child has displayed throughout the years. How often did she cry when she was 6 months? How about when she was 2 years old? How about when she was 7? Most kids probably cry every day at 6 months, just multiple times per week at 2 years, and only rarely at age 7.
So the question for our study was: Are kids at high-risk for depression different than their peers in their development of negative and positive affect? We were expecting that at risk kids would show more negative affect and less positive affect than their peers. Specifically, we were expecting that at risk kids would not show the typical increases in positive affect or the typical decreases in negative affect across the years that are observed in typically developing kids.
We were wrong. At least partially.
To our surprise, the high-risk kids show the same developmental trends as their peers. Specifically, their negative affect decreased over time and the positive affect increased over time as is expected in most low-risk kids. Also surprisingly, the levels of negative affect in any given year did not differ between the high-risk and the low-risk kids. So, the negative affect of the high-risk kids decreased over time in a typical fashion and these kids were not any sadder than their low-risk peers.
But we saw a real difference when we looked at positive affect. The high-risk kids looked just like their peers in that their levels of positive affect increased over time. Each year, the high-risk kids showed more and more positive affect as expected in most low-risk kids. But at any given year, the high-risk kids showed significantly less positive affect than their low-risk peers. So although their levels of happiness increased over time, high-risk kids were significantly less happy than their peers.
We believe then that high levels of sadness may not be playing an important role in the development of depression among these high-risk kids. Instead, it is low levels of happiness that may be a contributor to depression in these kids.
The clear implication to parents is that we should be attentive to kids happiness just as much as we are to their sadness. Your child may not be sad, but is he happy?
The Reference: Olino, T., Lopez-Duran, N., Kovacs, M., George, C., Gentzler, A., & Shaw, D. (2011). Developmental trajectories of positive and negative affect in children at high and low familial risk for depressive disorder Journal of Child Psychology and Psychiatry, 52 (7), 792-799 DOI: 10.1111/j.1469-7610.2010.02331.x