Unwanted mental intrusions (UMIs) are the normal variants of obsessions in Obsessive-Compulsive Disorder (OCD), preoccupations about defects in Body Dysmorphic Disorder (BDD), images about illness in Hypochondriasis (HYP), and thoughts about eating in Eating Disorders (EDs). The aim was to examine the similarities and differences in the functional links of four UMI contents, adopting a within-subject perspective. : 438 university students and community participants ( = 29.84,  = 11.41; 70.54% women) completed the Questionnaire of Unpleasant Intrusive Thoughts (QUIT) to assess the functional links (emotions, appraisals, and neutralizing/control strategies) of the most upsetting UMIs with OCD, BDD, HYP and EDs-contents. : HYP-related intrusions caused the highest emotional impact, OCD-related intrusions were the most interfering, and EDs-related intrusions interfered the least. The four UMI were equally ego-dystonic. Women appraised OCD-related intrusions more dysfunctionally, but men appraised the four intrusive contents similarly. All UMI instigated the urge to "do something", to keep them under control and/or neutralizing them. : Similarities among the functional links of intrusions related to OCD, BDD, HYP and EDs contents support their transdiagnostic nature and they might contribute to understanding common factors in these disorders.