ISTANBUL, TURKEY – Researchers from Bezmialem Vakif University have discovered significant differences in microRNA expression patterns between female patients with obsessive-compulsive disorder (OCD) and healthy controls, potentially offering new pathways for diagnostic biomarker development (Korkmaz et al., 2025). The study, published in Neuroscience journal, analyzed blood samples from 22 OCD patients and 20 healthy controls, revealing that miR-132 was significantly upregulated while miR-125b-5p was downregulated in patients with the disorder.
Obsessive-compulsive disorder affects approximately 3% of the global population and is characterized by persistent intrusive thoughts (obsessions) and repetitive behaviors (compulsions). Current treatment approaches include selective serotonin reuptake inhibitors (SSRIs) and cognitive-behavioral therapy, yet 40-60% of patients continue to experience symptoms despite treatment. This treatment resistance has prompted researchers to explore molecular biomarkers that could improve both diagnosis and therapeutic approaches for this debilitating condition.
The research team employed quantitative real-time polymerase chain reaction (qRT-PCR) to measure expression levels of three specific microRNAs: miR-132, miR-125b-5p, and miR-21-3p. Additionally, they measured plasma concentrations of serotonin and dopamine, two neurotransmitters known to play crucial roles in OCD pathophysiology. The study focused exclusively on female participants to control for gender-related differences in OCD prevalence and symptom presentation, as research indicates higher rates of the disorder among women compared to men.
MicroRNA Function in Neural Regulation
MicroRNAs are small non-coding RNA molecules approximately 19-25 nucleotides in length that regulate gene expression by binding to messenger RNA targets. These regulatory molecules play essential roles in controlling protein production and maintaining cellular homeostasis throughout the body, including the nervous system. In neuropsychiatric disorders, altered microRNA expression can disrupt normal brain function by affecting neurotransmitter systems, synaptic plasticity, and neuronal communication pathways.
The specific microRNAs examined in this study were selected based on their known involvement in neurological processes relevant to OCD. miR-132 has been previously associated with neuronal differentiation, synaptic plasticity, and stress responses, while miR-125b-5p plays roles in neuronal development and has been implicated in various psychiatric conditions including schizophrenia and major depressive disorder. The third target, miR-21-3p, is involved in cellular stress responses and apoptosis regulation.
Research findings showed that miR-132 expression was significantly elevated in OCD patients compared to healthy controls, consistent with previous studies linking this microRNA to stress-related psychiatric disorders. The upregulation of miR-132 may reflect altered neuroplasticity mechanisms in OCD, as this microRNA influences brain-derived neurotrophic factor (BDNF) signaling pathways that are crucial for neural adaptation and synaptic strength modification.
Neurotransmitter Level Analysis
The study revealed significantly higher plasma serotonin concentrations in OCD patients compared to healthy controls, supporting existing evidence for serotonergic system dysfunction in the disorder (Korkmaz et al., 2025). Serotonin, a neurotransmitter produced primarily in the gut but also synthesized in the brain, regulates mood, anxiety, and compulsive behaviors through its action on various receptor subtypes distributed throughout the nervous system.
Importantly, the majority of study participants were receiving pharmacological treatment at the time of blood collection: twelve patients were taking sertraline (50 mg daily), six were on clomipramine (225 mg daily), and two were receiving fluoxetine (20 mg daily). These medications are all designed to increase serotonin availability in synapses by blocking reuptake transporters, which could contribute to the observed elevation in plasma serotonin levels. This medication effect represents both a limitation and a real-world reflection of clinical OCD management.
Dopamine levels did not show significant differences between groups, although researchers identified a positive correlation between dopamine concentrations and Yale-Brown Obsessive Compulsive Scale (Y-BOCS) scores within the OCD patient group. This correlation suggests that higher dopamine levels may be associated with more severe symptom presentation, supporting theories about dopaminergic dysfunction in OCD pathophysiology. The Y-BOCS is a standardized clinical assessment tool that measures obsession and compulsion severity on a scale from 0 to 40.
Biomarker Potential and Diagnostic Applications
Receiver operating characteristic (ROC) curve analysis demonstrated that miR-125b-5p showed superior diagnostic potential compared to miR-132 in distinguishing OCD patients from healthy controls. ROC analysis is a statistical method used to evaluate diagnostic test performance by plotting sensitivity (true positive rate) against specificity (true negative rate) across different threshold values. Higher area under the curve values indicate better diagnostic accuracy.
The downregulation of miR-125b-5p in OCD patients may reflect disrupted neuroplasticity mechanisms, as this microRNA normally functions to protect against age-related inflammatory processes in the brain. Previous research has linked miR-125b-5p downregulation to various neuropsychiatric conditions, including Alzheimer’s disease and tic disorders in children. The consistent pattern of reduced expression across different brain-related disorders suggests this microRNA plays a crucial role in maintaining normal neural function.
However, the researchers acknowledge that these microRNAs are not specific to OCD, as similar expression changes have been observed in other psychiatric disorders including depression, schizophrenia, and autism spectrum disorders. This lack of specificity represents a significant challenge for developing OCD-specific diagnostic tests based solely on microRNA expression patterns. Future research will need to identify combinations of biomarkers that can distinguish OCD from other psychiatric conditions.
Molecular Mechanisms and Therapeutic Implications
The study revealed an important difference in the relationship between microRNAs and serotonin levels between healthy controls and OCD patients. In healthy individuals, all three studied microRNAs showed positive correlations with serotonin concentrations, suggesting normal regulatory relationships between these molecular systems. However, these correlations were absent in OCD patients, indicating disrupted communication between microRNA regulatory networks and serotonergic neurotransmission.
This disruption may occur through several molecular pathways. miR-132 is known to regulate p250GAP, a protein that influences dendritic spine morphology and synaptic plasticity, thereby affecting serotonin receptor sensitivity. Additionally, miR-132 modulates expression of MeCP2, an epigenetic regulator involved in serotonin synthesis and reuptake pathways. These regulatory disruptions could contribute to the abnormal serotonin signaling observed in OCD.
The findings suggest that microRNA-based therapeutic approaches might offer new treatment strategies for OCD patients who do not respond to conventional medications. By targeting specific microRNAs involved in neurotransmitter regulation, future therapies could potentially restore normal neural communication patterns. However, such approaches would require extensive development and safety testing before clinical application.
Study Limitations and Future Research Directions
Several important limitations affect the interpretation of these findings. The study included only female participants, which limits generalizability to male OCD patients who may exhibit different molecular patterns. Additionally, the absence of medication-naive patients prevents clear separation of disorder-specific biomarker changes from treatment effects. The relatively small sample size (22 patients, 20 controls) may have limited statistical power to detect subtle differences in biomarker expression.
The research team acknowledges that inflammatory pathways may also contribute to OCD pathophysiology, as elevated levels of inflammatory markers such as interleukin-6, tumor necrosis factor-alpha, and C-reactive protein have been reported in OCD patients. Future studies should examine inflammation-related microRNAs such as miR-146a and miR-155, which regulate neuroimmune responses and could provide additional biomarker candidates.
Researchers emphasize the need for larger studies that include both male and female participants, medication-naive patients, and appropriate psychiatric control groups to distinguish OCD-specific molecular signatures from those shared across multiple disorders. Integration of neuroimaging data with molecular biomarker profiles could provide more comprehensive understanding of how genetic and environmental factors interact to produce OCD symptoms.
Clinical Translation and Healthcare Impact
The potential development of microRNA-based diagnostic tests offers several advantages for clinical practice, including ease of application, relatively low cost, and rapid results compared to current diagnostic approaches that rely primarily on clinical interviews and behavioral assessments. Blood-based biomarker tests could provide objective measures to support clinical diagnosis, particularly in cases where symptom presentation is unclear or overlaps with other psychiatric conditions.
However, translation of these research findings into clinical practice will require extensive validation studies across diverse populations and healthcare settings. Regulatory approval processes for diagnostic biomarkers typically require demonstration of clinical utility, meaning the tests must improve patient outcomes beyond current standard-of-care approaches. Cost-effectiveness analyses will also be necessary to determine whether biomarker testing provides sufficient value to justify implementation in healthcare systems.
The research contributes to growing understanding of OCD as a neurobiological disorder with measurable molecular signatures rather than simply a behavioral condition. This perspective could help reduce stigma associated with mental health conditions by emphasizing their biological basis and promoting evidence-based treatment approaches. As precision medicine approaches continue to develop in psychiatry, molecular biomarkers may eventually enable personalized treatment selection based on individual patient characteristics.
Key Takeaways
- Research demonstrates miR-132 upregulation and miR-125b-5p downregulation in female OCD patients, with miR-125b-5p showing superior diagnostic accuracy through ROC analysis.
- Study limitations include female-only participants, medication effects on biomarker levels, and small sample size potentially affecting statistical power and generalizability.
- Neuroscience experts indicate disrupted microRNA-serotonin correlations in OCD patients suggest altered molecular regulatory networks contributing to disorder pathophysiology and treatment resistance.
Reference
Read the full study published in the July 2025 issue of Neuroscience:
Nur Damla Korkmaz, Birsen Elibol, Zeynep Durmus, Abdullah Ozdemir, Fahri Akbas, Sinan Guloksuz, Cigdem Dilek Sahbaz,
Evaluation of potential biomarker miRNAs and the levels of serotonin and dopamine in female patients with obsessive–compulsive disorder, Neuroscience, 2025, ISSN 0306-4522, https://doi.org/10.1016/j.neuroscience.2025.07.001.
