A longitudinal cohort study from the Netherlands has found that depression in patients aged 55 or older often goes untreated in primary care and has a poor prognosis.

Patients with a score >5 on the geriatric depression scale-15 were invited for a diagnostic interview carried out by trained interviewers using the PRIME-MD. A total of 234 fulfilled the criteria for major depression and were followed up at 6-monthly intervals over 3 years. Recovery was defined as no longer fulfilling the PRIME-MD diagnostic criteria for major depression plus a Montgomery Asberg depression rating score below 10.

The median duration of a major depressive episode was 18 months. Around a third, 35%, of the depressed patients had recovered at 1 year; 60% at 2 years, and 68% at 3 years.

Only 40% of the patients were receiving treatment at baseline. Of the patients who were still depressed at the 3-year follow-up, only 37% were receiving treatment.

One possible explanation of the low numbers receiving treatment is that the diagnostic tool was overdiagnosing depression. The PRIME-MD is the original clinician-administered version of the PHQ-9 with the same number of diagnostic criteria i.e. 5 of 9 during the past 2 weeks but with a higher threshold of 'nearly every day' rather than 'more than half the days'. As this is equivalent to a PHQ-9 score 15,³ the concerns regarding overdiagnosis by the PHQ-9, where the diagnostic threshold is set at 10, should not apply.¹

The authors suggest that the poor prognosis can be linked to inadequate treatment. It is well recognised that only a small proportion of older patients with depression receive treatment, either because of the attitude of the patient and/or doctor or diagnostic difficulties.² An audit in our practice found that only 18 out of 119 patients commenced on antidepressants (15%) were ≥ 65 years.

Use of assessment tools to define strict diagnostic and recovery thresholds in the clinical, as opposed to research, setting may exacerbate the problem. DSM IV may underdiagnose depression in the elderly³ and it has been argued that we should adopt a lower threshold for diagnosis.⁴ Depression often follows a relapsing-remitting course and many patients deemed to have recovered will have persisting sub-threshold symptoms.