OBJECTIVE: Two issues that may influence the diagnosis of depression in
the medically ill are 1) the severity with which symptoms must be expressed
before they are considered clinically significant and 2) how to deal with
somatic symptoms that may be caused by medical illness. This study used
different approaches to case identification to examine prevalence rates for
major and minor depression in a group of terminally ill cancer patients.
METHODS: Semistructured diagnostic interviews were conducted with 130
patients receiving palliative care. Diagnoses according to the Research
Diagnostic Criteria (RDC) were compared with diagnoses according to
Endicott's revised criteria (which involve replacing somatic symptoms with
non-somatic alternatives) when either a low-severity or a high-severity
threshold for classifying RDC criterion A symptoms was used. RESULTS: A
low-threshold (less stringent) diagnostic approach greatly increased the
overall prevalence of major and minor depressive episodes with both the RDC
and the Endicott criteria. With high thresholds, the RDC and the Endicott
criteria were equivalent, whereas with low thresholds the Endicott
substitutions identified fewer cases of major (but not minor) depression.
CONCLUSIONS: Small differences between investigators in the applications of
symptom-severity thresholds can result in large differences in prevalence
rates for depression. However, the inclusions of somatic symptoms in the
diagnostic criteria inflates the rates of diagnosis only when these
symptoms are used in conjunction with a low- threshold approach.