Data on associations between inflammation and depressive symptoms largely originate from high income population settings, despite the greatest disease burden in major depressive disorder being attributed to populations in lower-middle income countries (LMICs).

We assessed the prevalence of low-grade inflammation in adults with treatment-resistant depression (TRD) in Pakistan, an LMIC, and investigated associations between peripheral C-reactive protein (CRP) levels and depressive symptoms.

This is a secondary analysis of two randomised controlled trials investigating adjunctive immunomodulatory agents (minocycline and simvastatin) for Pakistani adults with TRD (n = 191). Logistic regression models were built to assess the relationship between pre-treatment CRP (≥ or <3 mg/L) and individual depressive symptoms measured using the Hamilton Depression Rating Scale. Descriptive statistics and regression were used to assess treatment response for inflammation-associated symptoms.

High plasma CRP (≥3 mg/L) was detected in 87% (n = 146) of participants. Early night insomnia (odds ratio 2.33, 95% CI 1.16–5.25), early morning waking (odds ratio 2.65, 95% CI 1.29–6.38) and psychic anxiety (odds ratio 3.79, 95% CI 1.39–21.7) were positively associated, while gastrointestinal (odds ratio 0.38, 95% CI 0.14–0.86) and general somatic symptoms (odds ratio 0.34, 95% CI 0.14–0.74) were negatively associated with inflammation. Minocycline, but not simvastatin, improved symptoms positively associated with inflammation.

The prevalence of inflammation in this LMIC sample with TRD was higher than that reported in high income countries. Insomnia and anxiety symptoms may represent possible targets for personalised treatment with immunomodulatory agents in people with elevated CRP. These findings require replication in independent clinical samples.

There has been increased interest in repurposing anti-inflammatories for the treatment of bipolar depression. Evidence from high-income countries suggests that these agents may work best for specific depressive symptoms in a subset of patients with biochemical evidence of inflammation but data from lower-middle income countries (LMICs) is scarce. This secondary analysis explored the relationship between pretreatment inflammatory markers and specific depressive symptoms, clinical measures, and demographic variables in participants with bipolar depression in Pakistan.

The current study is a cross-sectional secondary analysis of a randomized controlled trial of two anti-inflammatory medications (minocycline and celecoxib) for bipolar depression (n = 266). A series of logistic and linear regression models were completed to assess the relationship between C-reactive protein (CRP) (CRP > or < 3 mg/L and log10CRP) and clinical and demographic features of interest and symptoms of depression. Baseline clinical trial data was used to extract clinical and demographic features and symptoms of depression were assessed using the 24-item Hamilton Depression Rating Scale.

The prevalence of low-grade inflammation (CRP > 3 mg/L) in the sample was 70.9%. After adjusting for baseline body mass index, socioeconomic status, age, gender, symptoms related to anhedonia, fatigue, and motor retardation were most associated with low-grade inflammation.

Bipolar disorder (BD) patients from LMICs may experience higher rates of peripheral inflammation than have been reported in Western populations with BD. Future trials of repurposed anti-inflammatory agents that enrich for participants with these symptom profiles may inform the development of personalized treatment for bipolar depression in LMICs.