How Emotion Regulation and Illness Identity Shape Mental Health in Adults with Congenital Heart Disease

Background/Objectives: Adults with congenital heart disease (ACHD) are at increased risk for mental health problems, particularly depression and anxiety. Emerging evidence suggests that psychological rather than purely medical factors may play a decisive role in explaining individual differences in emotional adjustment. However, comprehensive models integrating multiple cognitive and emotional domains remain scarce. This study aimed to identify the psychological variables most strongly associated with depressive and anxiety symptoms in ACHD when considered simultaneously to inform priorities for psychosocial interventions. Methods: A total of 1136 ACHD (aged 18–85 years; 59.7% female) from the National Register for Congenital Heart Defects, Berlin, completed an online survey assessing depression, anxiety, emotion regulation, illness perceptions, and illness identity. Correlational and multiple regression analyses were conducted, controlling for sociodemographic characteristics, CHD severity, and secondary diseases. Significance level for regression models was set at p < 0.025 due to Bonferroni correction. Results: Rumination showed the strongest positive correlations with both depression and anxiety, whereas acceptance was most negatively correlated. In multiple regression analyses, rumination (highest unique variance explanation with semi-partial R2 = 0.068 resp. 0.072) and illness engulfment emerged as the most strongly associated predictors of depressive and anxiety symptoms. Illness-related concerns were not significant predictors. Conclusions: The findings highlight the key role of repetitive negative thinking and an engulfed illness identity in the development of emotional distress among ACHD. Psychotherapeutic interventions targeting rumination, fostering psychological distance from illness identity, and promoting a multifaceted self-concept may be particularly beneficial in this population.