BackgroundA large proportion of patients with eating disorders (ED) report experiences of childhood trauma. Latent trajectory analysis in ED samples reveals the complexities in course and outcome and can explore the long‐term impact of adverse experiences in childhood.MethodA total of 84 patients with longstanding ED were included. ED symptoms were assessed by the Eating Disorder Examination interview at discharge from inpatient treatment, and at 1‐, 2‐, 5‐, and 17‐year follow‐up, respectively. Change over time was examined using growth mixture modeling, allowing the number of trajectories to emerge through the data. Prevalence of childhood trauma was assessed, and its relation to class membership was tested.ResultsWe identified four distinct classes: patients with (a) a continuous improvement in the entire follow‐up period, and scores within normal range at the end, “continuous improvement” (54.8%); (b) a high symptom level at baseline and moderate decrease over time, “high and declining” (22.6%); (c) initial ED scores below clinical cut‐off and stable symptoms throughout the course, “consistently low” (14.3%); and (d) with high scores initially, and a significant increase in symptoms over time, “high and increasing” (8.3%). A history of childhood sexual abuse (CSA) was overrepresented in classes with persistently high symptom levels and poor long‐term outcomeDiscussionPatients with longstanding ED displayed considerable diversity in trajectories of symptom change across 17 years. To improve long‐term outcome, enhanced treatment of sequelae from CSA seems essential.Public SignificancePatients with longstanding eating disorders displayed four different trajectories of change in a 17‐year follow‐up study. Although there were significant changes over time, the majority of patients remained within similar symptom levels as they presented with at discharge from inpatient treatment. Exposure to childhood maltreatment was common within the sample. Childhood sexual abuse predicted poor long‐term outcome, which highlights the importance of trauma informed care.