A two-year, longitudinal study of 8,803 English 16-year-olds found that socioeconomic adversity in childhood is associated with depression at the age of 18. The authors estimate, however, that one-third of this effect is mediated by an individual’s locus of control.
An external locus of control, which causes an individual to see outcomes in his world as being outside of his control, is associated with increased rates of depression. Those who experience economic difficulties before the age of five are more likely to develop an external locus of control and, therefore, depression. By contrast, those with an internal locus of control see themselves as being largely in control of outcomes and are therefore less prone to depression.
The authors note that though locus of control is thought to be a largely permanent individual trait, it is nevertheless not entirely immutable, especially during adolescence. Therefore, argue the authors, “depression prevention programs should include a component that addresses cognitive beliefs about control because shifting external [locus of control] orientation to internal could help to reduce the risk of developing depression.”
Given that those on the political right tend to have an internal locus of control, believing that their destinies are their own, it makes sense that conservatives tend to be happier than liberals, who hold the opposite view.