[Prevalence and diagnosis of depression in primary care. A critical comparison between PHQ-9 and GPs' judgement]

Up to 50 % of patients suffering from major depression are not recognised by their general practitioners. On the other hand general practitioners do rate some of their patients as depressive despite the fact that psychiatric diagnostic instruments do not. In this study we wanted to not only analyse the number and proportion of concordant diagnoses between GP and an established psychiatric diagnostic instrument (PHQ-9), but also to analyse the modalities of non-concordant diagnostic classifications.

34 participating GPs asked all their patients visiting them at one ordinary work-day to fill in a questionnaire that included the German version of PHQ-9. Independently GPs documented their diagnostic judgement. If they saw a mental affection, they were asked to choose between eight different affections, with depression being just one of them.

1 277 patients filled in the questionnaires; from these 902 questionnaires could be analysed, because a pair of GP and patient could be identified. The prevalence of major-depression in the study-population was 9 %. GPs and PHQ-9 diagnoses were concordant in 45 %. However, GPs rated two thirds of patients that were classified as depressed by the PHQ-9 as psychologically affected. In these patients they also devoted more than half of the consultation time to mental problems.

GPs do often not diagnose patients as depressive even though they clearly realise their mental affection. Simple explanations like lack of time or conscious or unconscious avoidance to make a psychiatric diagnosis cannot explain this phenomenon.