Last week I wrote a post about the importance of publishing null results, so I thought I should lead by example and share this article which has an interesting null result.
A lot of research on cardiovascular disease and depression over the years has shown the the two things are related. What is a little more uncertain is whether one represents a risk factor for the other. For example, does getting heart disease lead to a lower quality of life, which can influence mood? Or can clinical depression earlier in life be a predictor of developing heart disease later?
A recent study examined 431 older men (aged 69-86 years), all of whom already had depression. Of these, about half of them also had heart disease. They followed them up for 6 years and they found that the men with heart disease were not more likely to get depressed again in the follow-up period compared the men without heart disease. So, according to this study, heart disease doesn’t predict depression.
Now I am wondering if these authors could have examined this sample with another sample that wasn’t clinically depressed – to see if depression predicts developing heart disease! To me, that scenario makes a lot of sense theoretically. Depression is a stressful thing to go through, and has been shown to increase levels of inflammation even as early as adolescence. Heart disease is an inflammatory disease, so repeated episodes of depression seem likely to influence heart health. And in fact, a lot of research suggests this already; read a meta-analysis here and another one here.