Statistical methods
After completing the questionnaires by the samples, the data were entered into SPSS software, version 25. Fisher's exact test was used to measure the relationship between qualitative variables and independent sample t-test was used to compare the mean happiness scores in the intervention and control groups. Also, the comparison of the mean happiness score in the stage before and after the intervention in each group was performed using paired sample t-test. To compare the trend of changes and after removing the effect of other variables, generalized estimating equation (GEE) was used. A statistical significance level of 0.05 was considered.