Objective: Objective of this study is to identify relationship of microRNAs with nicotine use and disease status of major depression.
Method: The blood samples of 50 patients who were admitted to Mersin University Teaching Hospital Psychiatry Department and 41 healthy controls (HC) were collected . To establish better diagnosis and eliminate deficiency of Hamilton Depression Rating Scale (HDRS) (such as higher scoring of somatic and sleep-related items) we used both HDRS and Montgomery-Åsberg Depression Rating Scale (which is focused on core symptoms of depression). For accurate phenotyping, patients, who met diagnostic criteria for major depression according to DSM IV, HDRS score above 17, has no comorbid psychiatric and medical condition, never used psychiatric drugs before and has not take any medication for 1 month prior to blood sampling period were included. Subtypes like psychotic, melancholic, anxious, seasonal and atypical were excluded. HC was also consisted of individuals, who have no history of psychiatric and chronic medical condition, has not take any medications for 1 month prior to blood sampling period and whose HDRS score was under 7. All of the participants were asked whether they smoke or not. Patients were asked if they had previous episodes and any triggering stressor and previous episodes. Our microRNA analysis method is described in our poster named "MicroRNAs as Potential Biomarkers for Major Depressive Disorder". Mann Whitney U test was used for statistical analysis.
Results: Results of the first part of our study results are presented elsewhere (poster name: MicroRNAs as Potential Biomarkers for Major Depressive Disorder). We didn't find any significant relationship with nicotine use and microRNA levels. Stressor related microRNAs were mir320a and mir451a. Among patients, who had a history of previous episode, statistically significant microRNAs were mir17-5p, mir223-3p, mir320a and mir451a.
Conclusion: The other poster of us identified mir320a, mir451a, mir17-5p and mir223-3p as potential biomarkers for depression. Here we demonstrate that these mentioned microRNAs were related also with previous episodes. This result should be verified with also further studies. We didn't find any relationship between nicotine use and peripheral microRNA levels. Probably, Evaluation of both depressed and healthy individuals caused this confusion. Further studies investigating nicotine use only, among healthy controls could be helpful to understand nicotine-related peripheral microRNAs.