OCD is marked by persistent intrusive thoughts (obsessions) and compulsive behaviors that disrupt normal functioning and quality of life. Despite advances in serotonin reuptake inhibitors and cognitive behavioral therapy, about 60 percent of individuals continue to suffer from intractable symptoms. The urgent clinical need to address this resistant subset is propelling neuromodulation to the forefront of psychiatric innovation. By targeting dysfunctional neural circuits implicated in compulsion and anxiety, these interventions offer a circuit-based approach that transcends symptom management, aiming instead to recalibrate the underlying pathophysiology.

Transcranial direct current stimulation represents the gentlest of these neuromodulatory techniques, delivering low-intensity electrical currents through scalp electrodes to modulate cortical excitability. Targeted manipulations of regions such as the pre-supplementary motor area (pre-SMA) and orbitofrontal cortex (OFC) have been explored to dampen hyperactive cortico-striato-thalamo-cortical loops that drive compulsive behaviors. Despite promising mechanistic rationale, clinical trials so far have reported heterogeneous outcomes. The variability in electrode placement, current strength, and session duration complicates the interpretation of efficacy, underscoring the necessity for rigorous standardization protocols and larger placebo-controlled studies integrating electric-field modeling and objective neurophysiological biomarkers.

Repetitive transcranial magnetic stimulation, a noninvasive technique employing rapidly changing magnetic fields to induce focal electrical currents in cortical areas, has garnered regulatory endorsement following FDA approval for OCD indications in 2018. By modulating neuronal activity within key hubs such as the medial prefrontal cortex (mPFC), anterior cingulate cortex (ACC), dorsolateral prefrontal cortex (DLPFC), and supplementary motor area (SMA), rTMS holds particular promise in restoring balance within the cognitive control network that governs intrusive thought regulation. Meta-analyses reveal significant symptomatic improvements, although the optimal stimulation parameters remain under investigation. Researchers are now delving into personalized protocols guided by neuroimaging and electrophysiological signatures to refine therapeutic precision.

Deep brain stimulation stands as the most invasive but also the most potent intervention for severe, treatment-refractory OCD. This surgical procedure entails implanting microelectrodes into deep brain structures including the bed nucleus of the stria terminalis (BNST), ventral capsule/ventral striatum (VC/VS), nucleus accumbens (NAc), and subthalamic nucleus (STN), followed by chronic electrical stimulation via an implanted pulse generator. Rigorously controlled trials affirm sustained symptom reduction rates between 35 to 60 percent on the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), with about two-thirds of patients experiencing durable benefit. The paradigm is increasingly shifting towards diffusion tractography and connectomic analyses to target white-matter pathways that mediate clinical response, enhancing outcomes even amid anatomical variability.

A particularly exciting frontier in DBS research involves the advent of closed-loop systems capable of real-time neural monitoring and adaptive stimulation based on specific biomarkers within OCD circuits. Emerging data suggest that aberrant low-frequency oscillations could serve as reliable signals to trigger on-demand modulation, potentially minimizing side effects and optimizing efficacy. While still in early development phases, closed-loop DBS embodies the vision of dynamic, personalized neuromodulation attuned to fluctuating symptom states.

Across all these neuromodulatory methods, personalization stands out as the thematic cornerstone. The review highlights that one-size-fits-all approaches are insufficient given the heterogeneity of OCD presentations and underlying neuroanatomy. Integration of advanced neuroimaging, electrophysiology, and computational modeling into clinical workflows is imperative to enable precision psychiatry, tailoring interventions to individual brain circuitry profiles and symptom clusters. This integration promises to transform psychiatric treatment paradigms from symptomatic alleviation to mechanistic correction.

The safety profiles of these neuromodulation techniques vary but are generally favorable when conducted in controlled environments. tDCS is associated with mild skin irritation, rTMS may cause transient scalp discomfort or headache, and DBS carries surgical risks albeit low rates of serious adverse events like hemorrhage. Multidisciplinary care and long-term follow-up remain critical to optimizing outcomes, addressing neuropsychiatric comorbidities, and managing device-related complications.

Ethical considerations are paramount as neuromodulation techniques, especially invasive ones, raise important questions regarding informed consent, long-term cognitive and personality effects, data privacy, and equitable access. The high costs and specialized infrastructure limit availability largely to major academic medical centers, posing challenges for global implementation. The authors call for harmonized international standards, robust ethical frameworks, and expanded training initiatives to ensure responsible and equitable dissemination.

The review’s cautiously optimistic tone reflects a field on the cusp of remarkable advances. The convergence of neuroscience, engineering, and clinical medicine is ushering in an era where brain circuits can be precisely manipulated to alleviate the most refractory psychiatric suffering. This paradigm shift foresees a future in which neuromodulation is not a last resort but an integral component of a personalized, adaptive psychiatry that continuously monitors and adjusts treatment as neural states evolve.

Beyond the clinical implications, these findings intersect with broader neuroscientific endeavors aimed at decoding the neural substrates of compulsive behavior. The refinement of neuromodulatory therapies is fostering deeper insights into the functional architecture of brain networks underpinning OCD and related disorders. Emerging technologies and cross-disciplinary collaboration will continue to accelerate this reciprocal relationship between mechanistic understanding and therapeutic innovation.

As neurotechnology progresses towards miniaturization and increased sophistication, home-based or wearable neuromodulation devices may become viable adjuncts to clinical care, particularly for noninvasive applications like tDCS and rTMS. However, the implementation of such devices must follow stringent validation to ensure safety and efficacy, including ongoing remote monitoring by healthcare professionals. This trajectory aligns with broader trends in digital health and personalized medicine.

In summary, the review article “Neuromodulation techniques in obsessive-compulsive disorder: Current state of the art” offers a sweeping and balanced examination of the current landscape and future directions of neuromodulation therapies. It underscores the promise these interventions hold for those with treatment-resistant OCD, their technical complexities, and the imperative for rigorous scientific and ethical standards. As neuromodulation increasingly shifts from exploratory research into mainstream clinical practice, it epitomizes the transformation of psychiatry into a neurobiological and technologically empowered discipline.

Subject of Research: People

Article Title: Neuromodulation techniques in obsessive-compulsive disorder: Current state of the art

News Publication Date: 28 October 2025

References: http://dx.doi.org/10.61373/bm025y.0125

Image Credits: Carolina Leitão Viegas

Keywords: obsessive-compulsive disorder, neuromodulation, transcranial direct current stimulation, repetitive transcranial magnetic stimulation, deep brain stimulation, treatment-resistant OCD, precision psychiatry, brain circuits, closed-loop DBS, neuroimaging, electrophysiology, personalized medicine

Obsessive–compulsive disorder (OCD) is a debilitating neuropsychiatric condition characterized by intrusive obsessions and compulsions, and when resistant to conventional treatments, it poses a profound clinical challenge. Until now, the genetic factors that specifically contribute to treatment resistance in OCD, as compared to other mental disorders such as depression, bipolar disorder, or schizophrenia, have remained poorly understood. The present study aimed to address this gap by investigating the influence of genetic variants—particularly single nucleotide polymorphisms (SNPs)—within the HTR2A gene, which encodes a critical serotonin receptor implicated in cognitive and emotional regulation.

The study retrospectively analyzed a cohort of 210 individuals diagnosed with various TRMDs. This cohort included 72 patients with major depressive disorder, 62 with bipolar disorder, 37 with schizophrenia, 30 with OCD, and 9 with other psychiatric disorders. Extensive genetic screening was performed on blood samples via next-generation sequencing technology, focusing on three HTR2A SNPs: rs6314, rs7997012, and rs6311. These polymorphisms were selected due to their documented involvement in serotonergic signaling pathways and previous associations with psychiatric conditions.

Statistical analysis employing chi-square tests and both single- and multiple-SNP approaches revealed intriguing patterns of association. Notably, the rs7997012 SNP emerged as a robust genetic marker distinctly linked to TR-OCD. Individuals homozygous for the A allele (A|A genotype) at rs7997012 exhibited a dramatically higher likelihood—nearly seven times greater—of belonging to the TR-OCD group compared to those with the G|G genotype, a finding underscored by a highly significant p-value (< 0.001).

Moreover, when comparing the A|A genotype against a combined group of G|G and A|G genotypes, this elevated risk remained statistically significant, reinforcing the potential specificity of rs7997012 in identifying OCD patients with treatment resistance. These findings indicate that the rs7997012 polymorphism may serve not merely as a susceptibility marker but more importantly as a genetic discriminator separating TR-OCD from other mental health disorders exhibiting treatment resistance.

Beyond isolated SNP effects, the study delved into haplotype analyses of the combined genotypes from rs6314, rs7997012, and rs6311. The global haplotype association was significant, with the combined genetic variants collectively influencing OCD treatment resistance. Specifically, the G-G-C haplotype was associated with a reduced risk of TR-OCD relative to the reference G-G-T haplotype, suggesting complex gene-gene interactions within serotonergic pathways that modulate the clinical phenotype of OCD.

These insights are particularly consequential given the centrality of serotonin neurotransmission in both the pathophysiology of OCD and the mechanisms of action of many psychotropic medications. The HTR2A gene encodes the 5-HT2A receptor subtype, a critical receptor involved in serotonin-mediated signal transduction in the brain regions implicated in OCD, such as the orbitofrontal cortex, basal ganglia, and anterior cingulate cortex. Variations affecting the expression or function of this receptor could influence neuronal circuitry and cognitive control processes underlying obsessive–compulsive behaviors, thereby contributing to differential treatment outcomes.

The implications of this study extend beyond academic curiosity, hinting at the dawn of personalized medicine approaches for OCD. By identifying genetic polymorphisms that reliably distinguish treatment-resistant patients, clinicians could tailor pharmacological interventions, opting for agents targeting specific serotonin receptor subtypes or developing novel therapeutics aimed at correcting the dysfunctional signaling pathways uncovered by genetic profiling.

While the findings are preliminary and require replication in larger, ethnically diverse populations, they nonetheless elevate the HTR2A rs7997012 polymorphism as a prime candidate for future research on OCD’s biological substrates. It stimulates the broader scientific discourse on how different mental disorders with overlapping clinical features yet diverse molecular etiologies might be more accurately categorized and managed.

In practical terms, the implementation of genotyping for the rs7997012 SNP alongside other serotonergic markers could eventually become integrated into psychiatric diagnostic protocols, improving prognostic accuracy. Patients identified as carriers of risk alleles might be prioritized for more aggressive or alternative therapeutic strategies earlier in the course of the illness, aiming to circumvent the protracted suffering commonly associated with treatment-resistant OCD.

Furthermore, this research underscores the necessity of multidisciplinary approaches, combining psychiatry, genetics, and neurobiology, to tackle the complexity of psychiatric illnesses. It also highlights the transformative potential of next-generation sequencing technologies in unveiling subtle yet impactful genetic variations that modulate disease phenotypes.

In conclusion, this seminal investigation sheds light on the crucial role of the HTR2A gene’s polymorphisms, notably rs7997012, in delineating treatment-resistant obsessive–compulsive disorder from other resistant psychiatric conditions. By deepening our understanding of the serotonergic system’s genetic architecture, it opens new avenues for developing precision psychiatry models, heralding a future where mental illness treatment is as personalized and effective as interventions in other fields of medicine.

Strong evidence now positions the HTR2A rs7997012 A|A genotype as a significant biomarker for TR-OCD, offering hope that such genetic insights will translate into improved patient outcomes. As researchers continue to unravel OCD’s genetic underpinnings, targeted therapies built upon these discoveries promise to alleviate the burden of this often intractable disorder, making previously elusive recovery a tangible goal.

Subject of Research: The role of 5-hydroxytryptamine receptor 2A (HTR2A) gene polymorphisms in distinguishing treatment-resistant obsessive-compulsive disorder (TR-OCD) from other treatment-resistant mental disorders (TRMDs).

Article Title: The role of 5-hydroxytryptamine receptor 2A (HTR2A) gene polymorphisms in treatment-resistant obsessive–compulsive disorder: a comparative study with other treatment-resistant mental disorders.

Article References:
Del Casale, A., Gentile, G., Arena, J.F. et al. The role of 5-hydroxytryptamine receptor 2A (HTR2A) gene polymorphisms in treatment-resistant obsessive–compulsive disorder: a comparative study with other treatment-resistant mental disorders. BMC Psychiatry 25, 938 (2025). https://doi.org/10.1186/s12888-025-07301-5

Image Credits: AI Generated

DOI: https://doi.org/10.1186/s12888-025-07301-5