C-Reactive Protein as a Biomarker for Anhedonia in Treatment-Resistant Depression: A Clinical Approach Open Access

Abstract

Although depression is one of the most common and debilitating illnesses worldwide, less than half of depressed patients respond to first-line antidepressant or psychotherapy treatment (Congio et al., 2020).  Patients who do not respond to treatment are defined as treatment-resistant.  Treatment resistance is associated with high rates of anhedonia (Lally et al., 2014), or a decrease in the ability to feel pleasure, and decreased motivation to pursue rewarding activity. Anhedonia is thought to be related to decreased connectivity in the corticostriatal network of the brain, and this decreased connectivity is also associated with inflammation (Felger, 2017).  The purpose of the study was to assess C-reactive protein, an inflammatory marker, as a biomarker for anhedonia in patients with TRD. We hypothesized that patients with higher CRP levels would correlate with those with higher baseline anhedonia scores, that CRP values would positively predict anhedonia scores, and that CRP would uniquely predict anhedonic symptoms as compared to non-anhedonic symptoms. We analyzed 263 TRD patients’ baseline CRP levels and baseline anhedonic and non-anhedonic symptoms, as measured by the Beck Depression Inventory II. We ran both Spearman’s rho correlations and multiple regression analyses, with age, sex, BMI and whether or not a patient was diagnosed with inflammatory or inflammation-associated conditions as covariates. Although our hypotheses were incorrect when examining the overall sample, when we split the file into two groups based on whether or not a patient had an inflammatory or inflammation-associated condition, we found that CRP had a significant main effect on the variance in anhedonic scores, non-anhedonic scores, and total BDI in the non-inflammatory group, suggesting that CRP may be an indicator of depressive symptoms in patients without inflammatory conditions, but not for those with inflammatory conditions. This finding suggests that medical screening could be particularly important in determining when to use CRP as a biomarker for depression.

Table of Contents

Introduction...........................1

Methods..................................3

Participants.............................3

Procedure................................4

Measures.................................5

Analytic Plan...........................6

Results....................................7

Discussion...............................9

Limitations............................10

Future Directions...................11

References.............................12

Tables....................................16

Table 1..................................16

Figures...................................17

Figure 1.................................17

Figure 2.................................18

Figure 3 ................................19

Figure 4.................................20

About this Honors Thesis

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School	Emory College
Department	Psychology
Degree	B.A.
Submission	Honors Thesis
Language	English
Research Field	Health Sciences, Mental Health Psychology, Clinical
Keyword	Treatment-resistant depression psychology C-reactive protein clinical psychology depression CRP anhedonia TRD inflammation psychiatry
Committee Chair / Thesis Advisor	Treadway, Michael, Emory University
Committee Members	Craighead, Linda, Emory University Hershenberg, Rachel, Emory University

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