2.3. Randomization and blinding

A biostatistician, independent of our research, from the Research Center for Clinical Epidemiology (Peking University Third Hospital) generated the random allocation sequence (with a block size of four) using R Software version 3.4.2. Sealed envelopes, which are opaque and sequentially numbered, are used to conceal the random allocation sequence. The opaque sealed envelopes, with participants' enrollment order printed outside and randomly assigned group printed inside, will be numbered consecutively and attached to a strain. Researchers will enroll the eligible participants after baseline assessment, then separate and open each envelope from the strain in the sequence corresponding to the participant's baseline assessment order, and assign the eligible participant into either the intervention group or the waitlist control group. To ensure that the randomized sequence allocation was strictly followed, when the researcher opens the envelope, he/she will write the name, date, and reason on the bottom of the envelope.

The behavioral data evaluators and MRI/EEG/NIRS scanners are blinded to the group assignments.