This paper discusses the case of a 14-year-old girl who presented with severe depressive-catonia, social withdrawal, self-harm and significant weight loss of approximately 20 kg over six months. Previously diagnosed with anxiety and eating disorders, her hospitalization revealed a depressed mood and physical signs of self-harm. Despite unremarkable initial laboratory tests and nutritional support via parenteral and enteral feeding, the patient continued to lose weight, prompting further investigation. Imaging studies, including MRI and enterography, showed superior mesenteric artery (SAM) syndrome, characterized by duodenal obstruction due to compression between the aorta and the superior mesenteric artery. More importantly, the clinical presentation of SAM in this case may have resulted from severe anorexia and weight loss rather than being a precursor, a relationship that is debated in the literature. The management of SAM syndrome generally involves dietary interventions aimed to weight restoration, which may alleviate symptoms by reducing duodenal compression. As the patient adhered to a nutritional plan, her mood improved and thus enteral nutrition was suspended. This case highlights the need to consider SAM syndrome as a potential consequence of significant weight loss and psychological distress in adolescents with eating disorders.