Major depressive disorder has been linked with inflammatory processes, but it is unclear whether individual differences in levels of inflammatory biomarkers could help match patients to treatments that are most likely to be beneficial. The authors tested the hypothesis that C-reactive protein, a commonly available marker of systemic inflammation, predicts differential response to escitalopram (a serotonin reuptake inhibitor) and nortriptyline (a norepinephrine reuptake inhibitor).
C-reactive protein was measured in serum samples from 241 adult men and women with major depressive disorder randomly allocated to 12-week treatment with escitalopram (N=115) or nortriptyline (N=126). The primary outcome measure was the score on the Montgomery-Åsberg Depression Rating Scale (MADRS), administered weekly.
C-reactive protein level at baseline differentially predicted treatment outcome with the two antidepressants. C-reactive protein and its interaction with medication explained more than 10% of individual-level variance in treatment outcome. The authors suggest that this peripheral blood biomarker may contribute to improvement in outcomes of major depressive disorder by personalizing treatment choice.

.
Uher R, Tansey KE, Dew T, Maier W, Mors O, Hauser J, Dernovsek MZ, Henigsberg N, Souery D, Farmer A, and McGuffin P: An Inflammatory Biomarker as a Differential Predictor of Outcome of Depression Treatment With Escitalopram and Nortriptyline. Amer. J. Psychiatry 171(12): 1278-1286 (2014).

.
http://www.ncbi.nlm.nih.gov/pubmed/25017001