background In certain disorders the boundaries between thoughts, obsessions, overvalued ideas and delusions are not always clearly delineated.
aim To find out whether delusions can be distinguished from the convictions that often accompany anorexia nervosa, obsessive compulsive disorder (ocd), body dysmorphic disorder (bdd) and hypochondriasis, all of which apparently may involve impaired reality testing.
method The literature was reviewed with the help of PubMed, using as key words 'delusions' in combination with 'hypochodriasis', 'anorexia nervosa', 'body image', 'obsessive compulsive disorder' or 'body dysmorphic disorder'. We also searched the Tijdschrift voor Psychiatrie and references of the literature we used.
results A number of disorders can probably be classified on a spectrum ranging from nonpsychotic to psychotic. For instance, ocd, hypochondriasis, bdd and to a lesser degree anorexia nervosa can all be particularized as 'with good insight', 'with poor insight' or 'with psychotic features'.
conclusion Current practice in dsm-iv is to classify ocd, bdd or hypochondriasis and a delusional disorder as separate entities; this way of classifying seems to be an artefact. Our findings indicate that a dimensional system of classifying psychotic systems is preferable to a categorised system.