It is difficult to argue a priori knowledge when studies incorporate more diagnostic-based diagnoses versus symptom-based dimensional diagnoses. However, researchers Lee and Vaillancourt (2023) found that “approximately half of individuals with an eating disorder present with a comorbid personality disorder, most commonly (22%), borderline personality disorder (BPD)” (Lee & Vaillancourt, 2023). Observing individuals from an earlier developmental stage helps discover which disorder comes first. It makes sense that an individual would develop poor eating habits if they are experiencing severe personality disorder symptoms. On the other hand, not having enough nutrition can cause the body and brain to develop patterns similar to those seen in certain personality disorders. In Lee and Vaillancourt's longitudinal study of adolescents aged 14–18, which found that high levels of disordered eating predicted high BPD features, but the initial presence of BPD features was less predictive of later eating pathology. There is a clear bidirectionality between the two disorders; however, eating disorders tend to promote BPD patterns.