TDCS Interventions for Subthreshold Depressive Symptoms in Young Individuals.

Inclusion Criteria: * 1\) Be between the ages of 12-25; * 2\) is right-handed on the Edinburgh Handedness Inventory; * 3\) 2-4 of the 9 depressive symptoms defined by the American Diagnostic and Statistical Manual of Diseases, Fifth Edition (DSM-5), lasting more than 1 week; or more than 5 depressive symptoms lasting more than 1 week but less than 2 weeks (i.e., not meeting criteria for a major depressive episode) (by DSM-5 Clinical Semi-Definitive Interview (K-SADS-PL) (Gilbody et al., 2017, JAMA); * 4\) Hamilton Depression Scale (HAMD-24) 24 points≥ 8 points, \< 24 points; * 5\) Gender is not limited; * 6\) Subjects and their families voluntarily participate and sign the informed consent form. Exclusion Criteria: * 1\) Individuals with the following diagnoses according to DSM-5: psychiatric disorders due to organic diseases, substance-related and addictive disorders, neurodevelopmental disorders, schizophrenia spectrum and other psychotic disorders, bipolar disorder (assessed by K-SADS-PL); * 2\) Have two or more DSM-V-defined manic symptoms for 4 days but do not meet the criteria for hypomania or meet the DSM-V defined criteria for hypomanic symptoms for only 2-3 days; * 3\) Severe or unstable physical illness; * 4\) have a moderate or higher risk of suicide (as assessed by the Columbia Suicide Severity Scale); * 5\) Received transcranial direct current stimulation in the past three months (continuous intervention time: \>2 weeks); * 6\) Contraindications to transcranial direct current stimulation, such as brain implants, personal or family history of epilepsy; * 7\) Magnetic resonance scanning is contraindicated, such as in vivo metal implants.