In the Present State Examination Manual,Winget al.
(1974) have provided the most succinct definitions of psychopathological terms,and in an attempt to clarify the
issued of terminology their definitions of depressive states related to depressed mood,recent loss of interest,
self-depriciation,hopelessness and observed depression.There were a number of additional definitions provided
for neglect due to brooding,subjective anergia,slowness and underactivity,in efficient thinking,poor concentration
suicidal plans or acts,morning depression,social withdrawal ,guilt and other related symtoms.

    Wide discrepancies in the early literature on estimates of the prevalence of mental illness in different
communities were largely the consequence of the use of different diagnostic criteria. The development and use
of standardized research instruments linked to clearly stated diagnostic criteria led to less variation between
studies.However,considerable differences still exist between measures with the implication that comparisons between
studies can be made only if two studies have utilized the same basic measurement scale.

    Many research studies have based the definition of a 'case' of depression on certain score having been
attained on one of the large number of depression-ratin scales. The different construction of these scales and
the different individual items they include create major difficulties in comparing studies,unless they have been
developed in relation to clear criteria such as the DSM-IV ( American Psychiatric Associattion 1994).

    The majority of depression-rating scales contain a diverse collection of symptons,attitudes and feelings
and will produce high prevalence rates and a large proportion of false positives if case detection relies upon
them ( Snaith 1987 ).Kutner et al.(1985),studying depression and anxiety in dialysis patients,found that scales
containing disease realated items yielded exaggerated scores.