The applications of TMS in brain function assessment and treatment of mental disorders: a narrative review

Over the past several decades, monoaminergic system dysfunction has been considered a key factor in the pathophysiology of some mental disorders. However, the therapeutic efficacy of drug therapy based on the monoamine hypothesis is unsatisfactory. In 2008, FDA approved the application of the repetitive transcranial magnetic stimulation (rTMS) for the treatment of patients with depression. Since then, TMS as a non-invasive neuromodulation technique, has been widely used to treat patients with mental disorders and assess their brain functions. This review article outlined the stimulation modes and parameter settings of TMS, summarized the therapeutic effects of TMS on main mental disorders such as depression, bipolar disorder (BD), schizophrenia, attention deficit/hyperactivity disorder (ADHD), and autism spectrum disorder (ASD), and synthesized the cellular and molecular mechanisms of its therapeutic effects for the mental disorders mainly based on preclinical research. These mechanisms involve pathophysiological processes such as neurotransmitter expression, neuroinflammation, neurotrophic factor production, oxidative stress, and gene expression related to brain plasticity and apoptosis in the brain. Furthermore, it introduced the emerging applications that combine TMS with other non-invasive neuroimaging techniques to assess brain function, including mapping neural pathways, measuring cortical excitability, and evaluating brain neuroplasticity. These advances have facilitated real-time evaluation of the therapeutic efficacy of TMS and optimized its application in treating mental disorders.