Effect of Toxoplasmosis on Melatonin and Cortisol in Smoking Addiction

Abstract

Background: Toxoplasma gondii infection can cause changes in neurotransmitter levels in the brain, which can affect an individual’s behavior. Objectives: The aim of this study was to investigate the relationship between latent toxoplasmosis and cigarette addiction and its effect on cortisol and melatonin levels, which are known to be associated with nicotine addiction. Methods: The patient group consisted of 90 smokers who applied to the Alcohol and Substance Addiction Treatment and Education Center Unit of the Health Sciences University Training and Research Hospital. Individuals with any substance addiction other than smoking were excluded from the study. The control group included 82 volunteers who had not used any substances in the last year. Toxoplasma gondii positivity, as well as cortisol and melatonin levels, were investigated via enzymelinked immunosorbent assay of the serum samples taken from the study participants. The Z test and Fisher's exact test were used to determine statistical significance at P < 0.05. The independent-samples Kruskal-Wallis t-test was used to determine the relationship between cortisol and melatonin levels and T. gondii positivity. Results: Toxoplasma gondii immunoglobulin G was detected in 52 (57.8%) of the smokers and 23 (28%) of those in the control group. A statistically significant relationship was found between T. gondii positivity and smoking (P = 0.001). In the statistical evaluation, no relationship was found between T. gondii positivity and cortisol and melatonin in smokers. Conclusions: There is an association between T. gondii infection and smoking addiction, but this association is independent of melatonin and cortisol levels. © 2025 Elsevier B.V., All rights reserved.