Participants in the intervention group received a 28-day AI conversation intervention after completing the baseline questionnaire. We asked users in the intervention group to use the web link every day, upload the start and end times of their conversations with the AI bot and screenshots of their chats; users who chatted for more than 5 minutes were considered to have successfully punched in for that day. Participants who clocked more than 8 days in the first 14 days were allowed to complete the second questionnaire at the two-week mark. Similarly, participants who quit more than eight times between days 15 and 28 could complete the third questionnaire at the four-week mark. Therefore, all users in the intervention group who completed the third questionnaire received at least 16 AI conversation interventions.

The waiting group received the same intervention as the intervention group after a 28-day waiting period.

Douyin Xinqing is an AI dialog bot. Users can start chatting with the Douyin companion bot by clicking on the "Direct Message" on the homepage of their accounts on Douyin app.

After a user sends any message to the Douyin companion bot, it first asks the user about his or her mood and guides him or her to start chatting around his or her emotions. According to the situation described by the user, the companion bot expresses empathy, asks questions to guide the user to talk, and provides suggestions at the appropriate time. Users can also record their emotions every day and look back regularly to observe changes in their inner feelings. In addition, the Douyin companion bot can also identify crisis situations such as suicide and severe mental illness and, if necessary, guide users to call the hotline to obtain professional psychological assistance.

Depression was assessed with the Patient Health Questionnaire (PHQ-9). The PHQ-9 contains nine items scored on a scale from 0 (not at all) to 3 (almost every day) based on the self-reported frequency of depressive symptoms in the past 2 weeks. The total score ranges from 0 to 27, and scores above 10 indicate probable depression symptoms.

Anxiety was assessed with the Chinese version of the Generalized Anxiety Disorder Scale (GAD-7). The 7 items are rated on a 4-point scale ranging from 0 (never) to 3 (almost every day) to assess the frequency of anxiety symptoms in the past 2 weeks. The total score ranges from 0 to 21, and according to the established criteria, scores above 10 indicate probable anxiety symptoms.

Positive and negative moods were assessed with the Positive and Negative Affect Schedule (PANAS). The scale was categorized into two dimensions, positive (PA) and negative (NA), and each dimension was scored independently, with 9 items per dimension. All the items are rated on a 5-point scale ranging from 1 (few) to 5 (very much). The higher the subject's score on a subscale is, the stronger the associated emotion experienced.