While older generations have experienced relatively stable changes over the life cycle, younger generations are facing more stress and depression than ever before in the midst of rapid social change. The increasingly fragile mental health of modern people has been recognised as a major societal problem and should be given more attention as it affects personal behaviors such as impulse buying. The aim of this study was to investigate the effects of stress, depression and self-efficacy on impulse purchases of fashion products. A total of 205 questionnaires were analysed using statistical analysis methods such as ANOVA, cluster analysis and regression analysis within the SPSS statistical programme. Through factor analysis, four impulse buying factors were derived: planned, emotional, promotional and situational impulse buying. The main results are as follows. First, the comparison between the four groups derived from the stress and depression variables showed that those with higher levels of stress and depression had lower self-efficacy and those with lower levels of stress and depression had higher self-efficacy. Second, it was found that the high stress and depression group generally had higher levels of impulse buying and the low stress and depression group had lower levels of impulse buying. Thirdly, it was found that stress, depression and self-efficacy each had a significant effect on impulse buying, but the effect varied according to the type of impulse buying. There was a negative effect of self-efficacy on planned impulse buying, a positive effect of stress on emotional impulse buying, a positive effect of stress and depression on promotional impulse buying, and a positive effect of depression and self-efficacy on situational impulse buying. Given that negative and positive psychology affect impulse buying differently depending on the type of impulse buying, fashion brands should develop marketing strategies. Further research should explore the impact of more psychological mechanisms on shopping behaviour, with a focus on single-person households where depression may be more prevalent.