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Do depression questionnaires influence GPs' management?

Depression questionnaire scores have only a limited effect on GPs' decisions on whether or not to prescribe antidepressant drugs, a large study has suggested.

A previous history of depression increased the likelihood of treatment whereas elderly patients and those with CHD or diabetes were less likely to receive treatment.

The prescribing of antidepressant drugs in England has continued to rise, reaching 33.6 million items in 2007,1 and prompting concerns that this largely reflects overtreatment of patients with subthreshold depression. Conversely, only a minority of patients with major depression receive effective treatment.2 The QOF has sought to improve the targeting of antidepressants by incentivising GPs to use a validated measure of depression severity.

A total of 1,658 patients were assessed with the PHQ-9, 584 with the HADS and 52 with the Beck depression inventory. In all, 79.0% of those assessed with the PHQ-9 and 79.5% of those assessed with the HADS received a prescription for an antidepressant. The referral rates to specialist services were 23.7% and 20.4% respectively.

Prescriptions and referrals were significantly associated with higher severity scores. However, 83.5% of patients assessed with the PHQ-9 had a severity rating of moderate to severe, compared with only 55.6% of those assessed with the HADS.

Logistic regression analyses indicated that other factors influenced the decision whether or not to prescribe or refer. A previous history of depression increased the likelihood of treatment whereas elderly patients and those with CHD or diabetes were less likely to receive treatment.

The fact that an almost identical proportion of patients were given antidepressant treatment despite the large discrepancy between the severity ratings would suggest that the questionnaire scores had only a limited influence on the decision whether or not to prescribe. This may reflect a problem with the PHQ-9 threshold: the authors suggest that if this were raised to ? 12 this would correlate better with GPs' diagnostic thresholds.

The recently revised BAP guidelines recommend antidepressants as first-line treatment for patients with moderate to severe major depression (suggested by a PHQ-9 score ? 15). For patients with mild major depression (suggested by a PHQ-9 score of 10-14 where the criteria for major depression are met), antidepressants are a treatment option and should be considered if there is a prior history of moderate to severe recurrent depression, or if the depression has persisted for 2-3 months. Antidepressants should not be used as first-line treatment for patients with subthreshold depression: the threshold of diagnosis of major depression may roughly define the point at which antidepressants begin to be more effective than placebo.3

There are two pitfalls to avoid with these questionnaires. First, it is a mistake to regard the PHQ-9 or HADS as a gold standard and follow rigid management guidelines based solely upon the severity score. Second, if the cut-off score is set too low, as in the case of the PHQ-9, the score will rarely challenge our decision to prescribe and the depression indicator is likely to fail in its aim of improving targeting of antidepressant treatment. I would certainly think twice before initiating antidepressant treatment where the PHQ-9 score is below 15.

Kendrick T, Dowrick C, McBride A et al. Management of depression in UK general practice in relation to scores on depression severity questionnaires: analysis of medical record data. BMJ 2009; 338:b750

Reviewer

Dr Phillip Bland
GP, Dalton-in-Furness

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