Specific depression symptoms are neglected. They are usually summed into scores that purport to reflect the severity of depression, but this loses essential information and reflects a naive view of depression as a single disease. In a series of studies with Matthew Keller, we discovered that different precipitants resulted in different symptoms. The patterns were those predicted if different symptoms were aroused by slightly different challenges, in much the same way that various symptoms of a cold depend on where the virus is working its mischief. The notion that depression is a single syndrome is false.
More recently, I have had the privilege of working with Eiko Fried as his studies rapidly advance our understanding of depression symptoms. The papers below demonstrate that relying on sum scores conceals important findings. The problem arises from the belief that depression is one disease with one cause. A more modern evolutionary view instead analyzes depression symptoms individually, in terms of their precipitants, their adaptive and maladaptive significance, and how they influence each other.
- Fried, E. I., & Nesse, R. M (2015). Depression sum-scores don’t add up: Why analyzing specific depression symptoms is essential. BMC Medicine, 13(72), 1-11. (PDF)
- Fried, E. I. (2015). Problematic assumptions have slowed down depression research: why symptoms, not syndromes are the way forward. Frontiers in Psychology, 6(306), 1-11. (PDF)
- Fried, E. I., Nesse, R. M., Guille, C., & Sen, S. (2015). The differential influence of life stress on individual symptoms of depression. Acta Psychiatrica Scandinavica, 131, 465-471. (PDF)
- Fried, E. I., & Nesse, R. M. (2015). Depression is not a consistent syndrome: an investigation of unique symptom patterns in the STAR*D study. Journal of Affective Disorders, 172, 96–102. (PDF)
- Fried, E. I., Boschloo, L., van Borkulo, C. D., Schoevers, R. A., Romeijn, J.-W., Wichers, M. C., de Jonge, P., Nesse, R. M., Tuerlinckx, F., Borsboom, D. (2015). Commentary: “Consistent superiority of selective serotonin reuptake inhibitors over placebo in reducing depressed mood in patients with major depression.” Frontiers in Psychiatry, 6(117), 1–3. (PDF)
- Fried, E. I. (2014). Covert Heterogeneity of Major Depressive Disorder: Depression Is More Than the Sum-Score of its Symptoms. Dissertation. (PDF)
- Fried, E. I., & Nesse, R. M. (2014). The Impact of Individual Depressive Symptoms on Impairment of Psychosocial Functioning. PLoS ONE, 9(2), e90311. (PDF)
- Fried, E. I., Nesse, R. M., Zivin, K., Guille, C., & Sen, S. (2014). Depression is more than the sum score of its parts: individual DSM symptoms have different risk factors. Psychological Medicine, 44, 2067–2076. (PDF)