Based on the results of the previously published paper "Positive Emotions Training (PoET) as an online intervention to improve mental health: a feasibility study" (Niemann et al., 2023) the goal of this study was to examine the effects of the "Positive Emotions Training" on mental health in a randomized-controlled study. Furthermore, possible predictors for the efficacy of PoET are to be explored.

Hypotheses:

1. It was hypothesized that participants receiving PoET would show a significant increase in positive mental health factors at the second assessment point (T2) at end of the second training day.
2. Furthermore, participants receiving PoET are to be expected to show a significant decrease in depression, anxiety and stress symptoms at T2.
3. It was hypothesized that the changes in mental health factors remain stable up to the last assessment point (T3) three month after the training.
4. Lastly, it was hypothesized that there would be no significant changes in the positive or negative mental health factors in the control group at T2 and T3.
5. The possible predictors of the training's efficacy were not hypothesized, but examined in exploratory investigations.

Methods:

The final sample was n = 207 with n = 90 in the PoET group and n = 117 in the control. The control group did not receive any intervention in the experimental period, but was offered to participate in a later PoET. The allocation was randomized. Participants in the PoET group completed two online training sessions (3 hours each) via Zoom. Group size was about 25-30 people. The sessions included the following positive psychology constructs: happiness, humour, optimism, loving kindness and gratitude on the first day, and hope, self-efficacy, meaningfulness, forgiveness and resilience on the second day. All participants completed a questionnaire at the beginning of the first training session, at the end of the second one as well as three months after the second session. Participants were given an exercise booklet for all exercises (during the training sessions and at home). The one-week break between the two sessions was advertised as a "7-day-challenge" to improve the motivation in participants to exercise at home.

Data was collected pseudonymised via "qualtrics". Data analyses were conducted with RStudio. For the possible effects of PoET on mental health two-factorial repeated measures ANOVAs were conducted. For the exploration of possible predictors for the efficacy of the training, a hierarchical regression was conducted.

Inclusion Criteria:

• legal age (18), ability to use Zoom and all associated technology

Exclusion Criteria:

• none