Randomization and blinding
inpatient affective disorders
Study participants, who were patients of an inpatient affective disorders’ unit, were randomly assigned in a 1:1 ratio to either an experimental group receiving tDCS or a control group receiving sham stimulation. To mitigate potential bias in the results, especially experimental bias, each patient was assigned to one of the four stimulation devices (A, B, C, and D) based on the order of their inclusion in the study. Two of the four devices were tDCS (A and C), and the remaining two were sham stimulation devices (B and D). To ensure compliance with the quality criterion of reliability, all stimulation treatments were carried out by the same practitioner (H.S.) using the same devices, in the same rooms, and always on weekdays (Monday–Friday) between 2:00 and 4:00 PM. The same trial physician always collected the assessment questionnaires. During the trial, neither the patients, the practitioner, nor the trial physician were informed about the devices’ mode (sham stimulation or tDCS) or whether the treatment was real or simulated. This blinding status was maintained throughout the evaluation of the raw data, and disclosure only took place at the beginning of the final data analysis to further reduce possible experimental bias.