Are we over-diagnosing depression?

Do recent claims that 'sadness' is being wrongly diagnosed as depression have merit? Professor Andre Tylee investigates.

The argument that depression is being wrongly diagnosed in patients who are merely sad was recently made by Professor Gordon Parker, who runs the Black Dog Institute for the treatment of mood disorders at the University of New South Wales.

Case for over-diagnosis
It is Professor Parker's belief that sadness is normal, but has been medicalised by doctors who have lowered the threshold for a diagnosis of depression, increasing diagnosis and treatment in recent decades.

A major factor increasing depression diagnoses was the switch from categorising depression as either endogenous (melancholic) or reactive (neurotic), to categorising it as major or minor depending on the number of symptoms.

'This model of depression risks medicalising normal human distress and viewing any expression of depression as mandating treatment,' Professor Parker says.

Increased prescribing for depression is partly the result of marketing by pharmaceutical companies. The effectiveness of antidepressant drugs over placebo increases with severity of depression and the benefit of treatment for minor depression is unclear.

Case against over-diagnosis
Professor Ian Hickie, who runs the Brain and Mind Research Institute at the University of Sydney, and previous chief executive of the Beyondblue Australian national depression initiative, argued that increased diagnosis over the decades has led to more people remaining alive, but that many people are still missing out on treatment.

Professor Hickie believes doctors can differentiate sadness from clinical problems. Increased treatment for depression reduces suicide rates and increases productivity. In addition, increased diagnosis has reduced stigma, improved physical health outcomes, reduced associated alcohol and substance abuse and has led to wider public understanding.

Psychological and medical treatments are cost-effective. Information and psychological interventions on the internet are popular with the public.

Health practitioners see depression as a condition needing community-based intervention, helped by the advent of safer drugs. Prescriptions for antidepressants rose sharply in the nineties but have now slowed and there is no evidence of over-diagnosis.

Professor Hickie warns that under-diagnosis of severe depression still remains. Recognition of depression needs to be improved because for many patients depression is a life-long disabling condition starting in their late teens or early twenties. He advocates early intervention and proper staging as in cancer care.

Distinguishing depression
The case against over-diagnosis is convincing. Sadness is an everyday experience for many people but this is not the same as having depression.

GPs have been shown mainly to recognise moderate-to-severe depression in their patients. GPs in England are now rewarded by their contract for using a validated instrument to assess the baseline severity of depression, once recognised.

DSM IV criteria for a diagnosis of major depression require at least five symptoms to be persistent and pervasive for at least two weeks with associated loss of function.

Most doctors know that symptom severity and duration are both crucial to diagnosis and often assess the patient for longer than two weeks.

Marketing must have some influence on antidepressant prescribing rates. Nevertheless, evidence suggests that GPs are very good at identifying patients with moderate-to-severe depression for whom the evidence of benefit from antidepressant treatment is good. There is no evidence of high recognition rates of mild or sub-threshold depression.

Less severe depression of long duration (more than three months) often responds to antidepressants. Dysthymia, which by definition is present for at least two years, responds very well to drug treatment.

When to treat
The DoH-funded threshold for antidepressant treatment study (THREAD) should soon report on response to antidepressant medication in patients with mild-to-moderate depression in primary care, and factors that predict benefit.

In Australia, the Beyondblue campaign has worked with insurance companies to reduce stigma and we can learn from their experience. Psychological treatments are far from being over-provided in the UK and attempts are under way to improve access, through programmes such as the Improving Access to Psychological Therapies programme.

- Professor Tylee is professor of primary care mental health at the Institute of Psychiatry, Kings College London and physician to the High Support Rehabilitation Team at the Maudsley Hospital.

References
- Parker G, Hickie I. Is depression overdiagnosed? BMJ 2007;335:328-29.
- NICE, clinical guideline number 23. Depression: the management of depression in primary and secondary care.

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