Neurostimulation in the treatment of psychiatric disorders: Underlying mechanisms and critical analysis of circuit-based interventions.

Neurostimulation of targeted brain regions has emerged as a novel therapeutic approach to induce remission in patients with various psychiatric disorders. This strategy encompasses several modalities, including transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), deep brain stimulation (DBS), and transcranial focused ultrasound neurostimulation (tFUS), all of which aim to modulate dysfunctional neural circuits and restore activity toward physiological ranges. While the clinical efficacy of these techniques is increasingly documented, the mechanisms underlying their effects-beyond immediate changes in regional excitability-remain incompletely understood. Further, neurostimulation represents not only a technical advance, but also a conceptual shift in psychiatry, moving from interventions aimed at modulating neurotransmission or cognition toward circuit-based models of mental illness. This review surveys the current literature to clarify the mechanisms of action of neurostimulation across multiple levels of biological integration, ranging from large-scale neural circuits to cellular and subcellular processes. Subsequently, it explores innovative targets and emerging modalities that expand the scope of circuit-based interventions beyond traditional approaches. Finally, it engages in a critical epistemological reflection, addressing the conceptual challenges that accompany the translation of circuit-based models from neuroscience to clinical psychiatry.