tDCS in People With Subthreshold Depression

Depression-prone individuals will be invited and allocated to three groups, either the personalised transcranial direct current stimulation (tDCS) group, the conventional tDCS group, or the sham control group. After screening and at baseline prior to the tDCS sessions, participants will complete tests and questionnaires on depression symptoms, loneliness and mood. Eligible participants will also be invited to receive functional magnetic resonance imaging (MRI) in a 3-Tesla MRI scanner. There will be a maximum of 10 sessions to be completed after the screening and baseline measures. For both personalised tDCS group and the conventional tDCS group, tDCS with 2 milliampere (mA) intensity will be delivered for 20 minutes in each session. For sham control group, the protocol will be similar, except that the stimulation only happens in the first 30 seconds in each session. Especially for participants allocated to the personalised tDCS group, the stimulation site for each individual in this group may vary, depending on their brain activations and connectivity. The anodal stimulation sites for participants allocated to the conventional tDCS group and the sham control group will be F3 within the left DLPFC. Immediately after and also 3-months after completing all the tDCS sessions, participants will be invited to complete again tests and questionnaires on depressive symptoms in addition to loneliness and mood. Eligible participants will also be invited to receive functional MRI scanning in the 3T MRI scanner again. Participants will also be prompted to self-report daily their loneliness and mood levels throughout the study.