Bipolar disorder is a highly disabling psychiatric illness, and cognitive impairment is common in patients with bipolar depression as well as during remission, contributing substantially to functional disability and poorer prognosis. Currently, effective interventions specifically targeting cognitive deficits remain limited, highlighting the need for novel treatment strategies. Transcranial magnetic stimulation, a noninvasive neuromodulation technique, has shown potential benefits for depressive symptoms and cognitive functioning. Based on structural and functional neuroimaging evidence, this study proposes an individualized intermittent theta burst stimulation (iTBS) protocol targeting the primary visual cortex (V1) and its functional pathway to the hippocampus, combined with online cognitive training. This randomized, double-blind, parallel-group, sham-controlled trial will enroll 88 patients with bipolar disorder in remission phase and allocate them to active or sham stimulation. The intervention will be delivered over 5 days, with follow-up assessments through 6 weeks. The primary outcome is change in cognitive performance as measured by the Cambridge Neuropsychological Test Automated Battery (CANTAB). Secondary outcomes include changes in clinical symptom ratings, magnetic resonance imaging (MRI) biomarkers, and the incidence of adverse events. This study aims to evaluate the efficacy and safety of this targeted intervention and to provide evidence for precision treatment approaches to cognitive impairment in bipolar disorder.

Inclusion Criteria:

1: Age between 18 and 45 years; 2: Right-handed; 3: Meet the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria for bipolar disorder and are currently in a stable remission phase; 4: Hamilton Depression Rating Scale 24-item (HAMD-24) score < 8; 5: Young Mania Rating Scale (YMRS) score <= 7; 6: The participant and his/her legal guardian are willing to comply with the treatment procedures and provide written informed consent.

Exclusion Criteria:

1: Diagnosis of another primary psychiatric disorder judged by the investigators to be the predominant condition, with functional impairment exceeding that attributable to bipolar disorder; 2: Comorbid psychiatric disorders, including obsessive-compulsive disorder, personality disorders, anxiety spectrum disorders, intellectual disability, or substance use (dependence/abuse); 3: Inability to complete self-report symptom rating scales or the CANTAB cognitive assessment; 4: Prominent suicidal ideation (item 3 of the HAMD-24 >= 2); 5: History of severe physical illness or other medical conditions that may affect the central nervous system; 6: Neurological disorders or risk factors for seizures, such as a history of intracranial disease, head injury, abnormal electroencephalogram (EEG) findings, magnetic resonance imaging (MRI) evidence of structural brain abnormalities, or a family history of epilepsy; 8: Contraindications to MRI or transcranial magnetic stimulation, such as the presence of metallic or electronic implants (e.g., intracranial metallic foreign bodies, cochlear implants, cardiac pacemakers, vascular stents); 9: Receipt of electroconvulsive therapy (ECT) within 6 months prior to study enrollment; 10: Currently undergoing transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), or other neuromodulatory interventions; 11: Pregnant or breastfeeding women, and women of childbearing potential with a positive urine pregnancy test.

This study collects sensitive clinical, neurocognitive, and MRI data. Because the current informed consent, ethics approval, and institutional data governance do not permit external sharing of IPD. Study-level summary results will be disseminated via peer-reviewed publications.