The overall aim of the thesis was to add some pieces to the etiological puzzle of LCPD with special focus on vascular origin and hyperactivity. Furthermore we wanted to evaluate some consequences of LCPD in adulthood. Swedish registry data were used to identify a cohort of patients with the diagnosis of LCPD. This cohort was compared with a general population– based cohort without LCPD to assess the relative risk of cardiovascular diseases, blood or coagulation defects, injury, ADHD, depression and mortality. In a clinical study we assessed health-related quality of life (EQ-5D-3L), physical activity level (IPAQ) and screened for ADHD (ASRSv1.1) in 116 patients with a history of LCPD who were diagnosed or treated in Uppsala University Hospital between 1978 and 1995. The results confirmed our hypothesis: Patients with a history of LCPD had a 1.7-fold higher risk of cardiovascular diseases, and a 1.4-fold higher risk for blood or coagulation defects compared with gender- and age-matched individuals without LCPD. We found a 1.2-fold higher risk for injuries requiring hospital admission than in gender- and age-matched individuals without LCPD. The risk was more pronounced among females. Furthermore, we found a 1.5-fold higher risk for ADHD. Stratified analysis revealed a 2.1-fold higher risk for ADHD among females with LCPD than among females without LCPD. The risk for depression was 1.3-fold higher, and more pronounced among females with LCPD. Patients with LCPD had a slightly higher mortality risk with higher risk for death from suicide and cardiovascular causes. Patients with a history of LCPD reported a lower health-related quality of life and were more physically active than the Swedish population norm. 28% of 116 patients were likely to have ADHD or had already been diagnosed with ADHD. Both vascular and blood diseases could be present even in childhood and could, in combination with hyperactive behavior pattern and a high physical activity level, contribute to the etiology of LCPD. The lower health-related quality of life and higher risk for depression might reflect the mental burden of LCPD. Patients with LCPD have a higher mortality risk with higher risk for death from suicide and cardiovascular causes.