Frontal arachnoid cyst as an incidental finding in depression research

•Arachnoid cysts are the most common congenital incidental findings on brain scans and are considered benign structures.Recent research associates cysts with affective- and cognitive symptoms.On a brain MRI of a 32-year-old woman with depression, we found an arachnoid cyst on the right frontoparietal convexity.•The cyst was not associated with the depression but highlights the importance of excluding organic etiologies in depression.