Serum Interleukin-6 in Schizophrenia: Associations with Clinical and Sociodemographic Characteristics

BACKGROUND:Recentlyasignificant part of schizophrenia studies have been focused on the role of cytokines, especially interleukin-6 (IL-6). Some authors have suggestedapathogenetic role for IL-6 in schizophrenia and concluded that therapy that centers on suppressing IL-6 activity may prove beneficial for certain categories of patients with the disorder. However, many questions about whether the changes in IL-6 levels in schizophrenia are primary, related to symptoms or caused by therapy, are concomitant metabolic disorders, are related to smoking or other secondary factors remain unanswered. AIM:To assess the level of serum IL-6 in patients with schizophrenia in comparison with healthy controls, as well as to study its association with clinical and socio-demographic characteristics. METHODS:Some 125 patients with schizophrenia and 95 healthy volunteers were examined.Theevaluation of IL-6 was performed by enzyme immunoassay. All patients were assessed using standardized psychometric instruments. Information from patient medical records on the course of the disease and treatment wasanalyzed. RESULTS:Thelevel of IL-6 was significantly higher in the patients than in the healthy volunteers (z=2.58;p=0.0099), but among men the difference between the patients and volunteers was not significant. Statistically significant correlations were found between the level of serum IL-6 and the severity of the cognitive impairment of patients: (auditory ρ=–0.31;p=0.00063 and working memory ρ=−0.25;p=0.0065, hand-eye coordination ρ=−0.29;p=0.0011, verbal fluency ρ=−0.28;p=0.0019 and problem-solving capacity ρ=−0.22;p=0.013), total severity of schizophrenia symptoms (PANSS, ρ=0.22;p=0.016), PANSS positive subscale (ρ=0.18;p=0.048), and the age of manifestation (ρ=0.20;p=0.025) and disease duration (ρ=0.18;p=0.043).Thelevel of IL-6 was the lowest in patients treated with third-generation antipsychotics, and the highest in those treated withfirst-generation antipsychotics (H=6.36;p=0.042). Moreover, in hospital patients, the level of IL-6 was significantly higher than in outpatients and inpatients hospitals (H=18.59;p=0.0001). CONCLUSION:Thestudy confirmed that there are associations between the serum IL-6 level and schizophrenia, the age of the patient, duration of the disease and how late in one's life cycle it began manifesting itself, as well asanumber of clinical characteristics. Considering that IL-6isassociated withawide range of symptoms that are loosely controlled by antipsychotics, this biochemical marker needs to be studied to look into how closely its level tracks with an unfavorable course of schizophrenia. That would require further prospective studies.