Cluster analysis derived MMPI profile types were compared for three di
stinct illness populations: chronic low back pain (CLBP), mixed headac
he (HA), and cardiac disease (CD). Results replicated previous finding
s in the chronic pain and cardiac literatures. Differences between dia
gnostic groups and genders were found for the prevalence of the derive
d MMPI profile types. Results indicated that, in males, the two chroni
c pain groups had similar profile types and similar relative frequenci
es of these types, but both differed from the CD sample. The chronic p
ain groups tended to have a greater number of patients with pathologic
al and distressed MMPI profile types and a lesser representation in th
e subclinical profile type compared to the CD sample. Similar findings
were obtained for females, though the CLBP group tended to have a hig
her frequency of highly distressed, pathological profiles than either
the HA or CD groups. Results suggested that the MMPI may be a measure
of response to illness rather than reflecting predisposing personality
types for any given illness and that the higher frequency of highly d
istressed profiles in the chronic pain samples reflects the increased
suffering of those populations compared to other illnesses.