Systemic inflammation impacts anhedonia symptoms in depressed adults

Adults with major depressive disorder (MDD) and systemic inflammation appear to respond more to inflammatory stimuli. Psychologically, this sensitization affects anhedonia symptoms.

A team of investigators conducted a randomized controlled trial of 68 individuals with MDD. Participants were randomly allocated 1:1 to receive lipopolysaccharide (LPS; 0.8 ng/kg body weight) or placebo (saline) in a parallel-group, double-blind design.

The investigators also stratified participants according to baseline C-reactive protein (CRP) concentrations: high-CRP LPS (n=13), low-CRP LPS (n=19), high-CRP placebo (n=13), and low-CRP placebo (n=19). Blood was sampled at baseline, at 1, 1.5, 3.5, 6, and 24 h, and 1 week after LPS or saline administration. Psychological outcomes were also assessed concurrently.

Significantly higher increases were noted in self-reported anhedonia on the Snaith-Hamilton Pleasure Scale (SHAPS) and interleukin (IL)-6 levels between baseline and 1.5 h in the high-CRP vs low-CRP group receiving LPS. No significant differences were seen for tumour necrosis factor and IL-10.

The Montgomery-Åsberg Depression Rating Scale (MADRS) was not administered at 1.5 h. In secondary analyses, a significant group-by-condition-by-time interaction was observed, driven by a higher decrease in MADRS scores between baseline and 24 h in the high-CRP group.

“Depressed individuals with systemic inflammation appeared to be biologically primed to respond more strongly to inflammatory stimuli, and psychologically this sensitization impacted the symptom of anhedonia, the primary outcome,” the investigators said.