Although controversial, it is often argued that religious belief is a cause of greater happiness.1 However, we have found in two separate studies that both theism and atheism are correlated with fewer reported depressive symptoms than the in-between state of ‘existential uncertainty’.
In our first study, on the effect of religious conviction on the Beck Depression Inventory (BDI), there was an unanticipated ‘inverted-U’ relationship, where the most and least religious groups had fewest depressive symptoms. In the second, we devised an 11-item existential conviction scale (ECS) as a measure of the degree of certainty with which an individual feels they understand the basis of human life [http://www.hedweb.com/bgcharlton/ecsq]. Fifty-two subjects (24 male, 28 female; age 18–76 years) completed the ECS and BDI. All 10 of those who rated as depressed (‘mild’ depression, BDI score 10+) were roughly halfway between atheist and theist. There was a significant negative relationship between ECS and the BDI (Spearman rank correlation –0.44, p<0.2).
There are several plausible explanations for such an association. Most obviously, strong beliefs may protect against depression, or conversely, low mood may diminish strong beliefs. Alternatively, depressive symptoms and existential uncertainty may both be a consequence of confounding by systemic illnesses, because immune activation tends to cause malaise symptoms such as fatigue (leading to depressed mood) and impaired concentration (perhaps leading to greater uncertainty of beliefs).2–4 This hypothesis is currently being tested.