Table 6.

Potential biomarkers from microRNA studies in various MH-related disorders

Author name or study ID	Disorder	Molecular features/biological functions affected	Implications/key findings	Source
Pang et al. [163]	AD	hsa-let-7d, hsa-miR-144, hsa-miR-374a, and hsa-miR-106b targeting genes in pathways PI3K-AKT signaling pathway, MAPK signaling pathway, oxidative phosphorylation, synaptic vesicle cycle, cell–cell adhesion, cytokine-mediated signaling pathway, proteasome, arginine, proline metabolism and pentose phosphate pathway [163]	Analysis of two important regions of the brain—entorhinal cortex (EC) and hippocampus (HIP) of AD patients revealed microRNAs that targeted genes in specific pathways	Blood
Multiple studies: Forero et al. [55, 59, 60, 164]	MDD	DEGs in various brain regions. MicroRNAs including hsa-miR-32, hsa-miR-33, hsa-miR-122, hsa-miR-429 associated with MDD. These microRNAs also known to regulate other MDD genes including GABA receptors, NOTCH2 and HNRNPU [60, 164]. Other miRNAs implicated include hsa-miR-370, hsa-miR-411, hsa-miR-433, hsa-miR-487b and hsa-miR-539 [165]	Studies analyzed in the blood, amygdala, cerebellum, ACC and PFC regions revealed microRNAs linked to chronic stress and fear and GABA receptors linked to chronic stress and fear [55, 164]	Various brain regions
Wang et al. [166–168]	SCZ	hsa-miR409-3p [166–168] which targets genes associated with SCZ including FAM117B, GABRA1, GAD1, and NUMBL. hsa-miR-370 targets several SCZ associated genes including BDNF, NRG1 and SYN2 [166, 169]. Other microRNAs affected include miR-30e, miR-7, miR-195, miR-34a and miR-346	microRN As that targets genes associated with SCZ	Tissue; blood; blood
Multiple studies [61, 170]	MDD and BD	miR-652 [61, 170]	microRNA affected in both MDD and BD	Various sources (microRNA affected in both MDD and BD); blood
Kohen et al. [63]	SCZ, MDD and BD	miR-182	RNA-seq revealed this microRNA was found activated in patients with BD and healthy controls while downregulated in MDD and SCZ [63]	Brain tissue
Multiple studies [61, 62]	Multiple neuropsychiatric disorders	miR-132, one of the microRNAs regulating expression of BDNF, and targets the genes MAOA and SLC6A3	One of the key players in brain plasticity and implicated in neuropsychiatric disorders [61, 62]	Various sources (microRNA affected in both MDD and BD); various sources
Srivastav et al. [171]	ADHD	microRNAs regulated the gene expression of BDNF, DAT1, HTR2C, HTR1B and SNAP-25	These microRNAs were also linked to ADHD etiology [171]	Various sources
Nakata et al. [64]	ASD	miR-6126 downregulated in ASD	Study of microRNA expression in peripheral blood from adults with high functioning ASD compared with healthy controls	Blood
Gupta et al. [65]	ADHD	microRNAs associated with HPA axis regulation through FKBP5 were found to play a key role in PTSD	Circulatory microRNAs to play an important role in PTSD	Blood
Martin et al. [172]	PTSD	Four upregulated microRNAs (miR-19a-3p, miR-101–3p, miR-20a-5p and miR-20b-5p) and four downregulated microRNAs (miR-15b-3p, miR-125b-5p, miR-128-3p and miR-486-3p) in PTSD samples	Implications of microRNA dysregulation in PTSD patients	Blood