Has Research Found a Reliable Depression Biomarker in Boys?
A major obstacle in the prevention of depression is the lack of a predictive biomarker in individuals who later develop the disorder. British researchers have shown that the combination of a physiological biomarker—salivary cortisol—and the presence of depressive symptoms might be used to predict the development of major depression in adolescents.
Two cohorts (n=660 and 1,198) of British students (mean ages 13.7 and 14.5 years, respectively) participated in this longitudinal study. At baseline, early morning salivary cortisol was measured daily over a four-day period; subjects also completed the Moods and Feelings Questionnaire (MFQ) and a battery of other neuropsychological tests. Followup interviews were conducted one to three years later.
Subjects were fairly evenly distributed among four classes, representing “high cortisol” (mean approximately 4–6 ng/ml) or “low cortisol” (2–3 ng/ml), as well as high or low depressive symptoms.
The odds of developing major depression increased across the four classes, with the lowest risk in class 1 (low cortisol and low depressive symptoms, 31% of the sample) and the highest in class 4 (high cortisol and high depressive symptoms, 17%).
Sex differences were also apparent. Male students who had both elevated depressive symptoms and elevated cortisol levels had significantly greater odds of developing a diagnosis of MDD compared to boys with low symptoms and low cortisol (OR=14.7, 95% CI: 6.1–35.0).
In girls, only depressive symptoms were significantly correlated with the onset of depression (OR=3.5 or 3.9 for high or low cortisol, respectively).
The researchers also found that the students (both male and female) with elevated depressive symptoms and high cortisol demonstrated more “overgen-distriberal memory,” a tendency to recall general features of autobiographical events rather than specific details and suggest that efforts to enhance the specificity of memories in such individuals may be one way to intervene and, perhaps, prevent the onset of depression (Owens M et al, Proc Natl Acad Sci US 2014;111(9):3638–3643).
TCPR’s Take: This study is another in a recent wave of research to identify biomarkers of mental illness. Notably, this study takes into account multiple features (cognitive, emotional, endocrine) to define a specific depressive phenotype, something lacking in the present DSM and develops testable hypotheses for the prediction and possible prevention of major depression, even though it remains unclear why this particular combination increases the odds of depression in boys only.
This research also identifies a possible nonpharmacological approach— namely, cognitive training to target over general memory—to prevent later onset of depression.