| Summary: | Abstract
Background: Depression assessment in population studies is usually based on depressive
symptoms scales. However, the use of scales could lead to the choice of an arbitrary cut-off
point depending on the sample characteristics and on the patient diagnosis. Thus, the use of a
medical diagnosis of depression could be a more appropriate approach.
Objective: To validate a self-reported physician diagnosis of depression using the Structured
Clinical Interview for DSM-IV (SCID-I) as Gold Standard and to assess the factors associated to
a valid self-reported diagnosis.
Methods: The SUN Project is a cohort study based on university graduates followed-up through
postal questionnaires. The response to the question included in the questionnaire: Have you
ever been diagnosed of depression by a physician? was compared to that obtained through the
SCID-I applied by a psychiatrist or a clinical psychologist. The percentages of confirmed
depression and non-depression were assessed for the overall sample and according to several
characteristics. Logistic regression models were fitted to ascertain the association between
different factors and a correct classification regarding depression status.
Results: The percentage of confirmed depression was 74.2%; 95% confidence interval (95%
CI) =63.3-85.1. Out of 42 participants who did not report a depression diagnosis in the
questionnaire, 34 were free of the disease (%confirmed non-depression=81.1%; 95% CI=69.1-
92.9). The probability of being a true positive was higher among ex- smokers and non-smokers
and among those overweight or obese but the differences were not statistically significant.
Conclusion: The validity of a self-reported diagnosis of depression in the SUN cohort is
adequate. Thus, this question about depression diagnosis could be used in further
investigations regarding this disease in this graduate cohort study.
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