Abstract
Mindfulness-based therapy is a modified form of cognitive therapy that uses mindfulness practices such as awareness of present moment, meditation, and breathing exercises. This therapy was innitially formulated to address depression. However, this research was conducted with the aim of determining the effectiveness of mindfulness-based therapy on improving psychological symptoms and emotion regulation in individuals with borderline personality disorder. The current study was a semi-experimental study with a pre-test, post-test, follow-up design and a control group. The research sample consisted of 40 women diagnosed with borderline personality disorder at a psychiatric hospital in Tehran, selected through purposive sampling and randomly assigned to two groups: experimental group (20 individuals) and control group (20 individuals). Participants completed the Emotion Regulation Questionnaire and the Psychological Symptoms Questionnaire in the pre-test, post-test, and follow-up stages. The participants in the experimental group underwent 20 sessions of mindfulness-based therapy. The results showed that mindfulness-based therapy had a significant effect on improving psychological symptoms and emotion regulation in individuals with borderline personality disorder (p < 0.001). The results also indicated that mindfulness-based therapy leads to an increase in positive strategies and a decrease in negative strategies of emotion regulation in the post-test stage, and this effect persists in the follow-up stage.