Disturbances in inflammatory processes may play a role in the pathophysiology of psychiatric disorders. The neutrophil lymphocyte ratio (NLR) and C-reactive protein (CRP) are indicators of the systemic inflammatory response.

The current study was prepared based on the assumption that dysregulated immune function and elevated inflammation markers may be seen in substance use disorders.

Our aim was to investigate whether NLR and CRP are higher in patients diagnosed with substance use disorders than in healthy subjects.

The participants in the study included 115 male inpatients diagnosed with alcohol (n=41), heroin (n=46), or synthetic cannabinoid (n=28) dependence according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV-TR), and 32 healthy male volunteers. We used NLR and CRP as measures of systemic inflammation. Blood samples were taken on the next morning of admission for detoxification. Addiction severity was assessed using the Addiction Profile Index (API).

The difference between the groups with respect to NLR was statistically significant (P=0.014). Patients diagnosed with alcohol, heroin or synthetic cannabinoid dependence had similar NLR. Patients with alcohol or synthetic cannabinoid dependence had significantly higher NLR than healthy controls (P=0.001 and P=0.029, respectively). Patients with heroin dependence trended towards statistically significantly higher NLR compared to healthy controls (P=0.067). CRP levels did not differ significantly between the patient and control groups. NLR and CRP were not significantly correlated with API scores.

Our findings suggest that NLR is elevated in patients with substance use disorders in comparison to healthy controls.