Micro-RNAs (miRs) are involved in processes associated with MDD such as neural plasticity, neurogenesis, synaptogenesis and stress response. MiRs are detectable in biological fluids; however, no data is available regarding the use of plasma circulating miRs as markers of MDD, only whole blood or serum being reported so far.

We investigated plasma miR profiles as potential markers for MDD in patients treated with antidepressants.

To detect and characterize differentially expressed miRs in the plasma of MDD patients, before and after treatment with escitalopram.

Blood was collected from patients with MDD before and after 12 weeks of treatment. Plasma profiles of 1008 miRs were measured by real time PCR. The fold change of expression between time points was calculated and a paired t test was used for statistical significance. Gene targets and pathways were assessed in miRWalk2.0.

From 222 plasma miRs expressed, 40 were significantly different after treatment. Upregulated miRs (23) belonged to 43 pathways, down-regulated miRs (17) belonged to 46 pathways; the top 5 significant pathways identified being pathways in cancer, Wnt signalling, endocytosis, axon guidance and MAPK signalling. Six of these miRs are common to all five pathways: miR-146a-5p, miR-146b-5p, miR-221-3p, miR-24-3p, miR-26a-5p.

Our analysis of significant changes in plasma miRs after escitalopram treatment of MDD might open new avenues for the understanding of its mode of action and its side effects. To our knowledge, this is the first study to assess miRs affected by antidepressant treatment in plasma of MDD patients.

The authors have not supplied their declaration of competing interest.