Is Depression Under or Over-Diagnosed?

Medical Reviewer

Not so very long ago we were reading that depression was under-diagnosed and under-treated. During the past couple of months things appear to have changed. The John Hopkins Bloomberg School of Public Health now states that over-diagnosis and over-treatment of depression is common in the U.S. Likewise, the Canadian Task Force on Preventative Health Care state that routine screening for depression is not recommended for adults with no apparent depressive symptoms. Time to dig a little deeper.

Described by the study author Dr. Ramin J. Mojtabai as "staggering" results obtained from a study sample of 5,639 65+ year olds revealed that 6 out of every 7 with clinically diagnosed depression did not meet the 12-month major-depressive criteria, despite a majority reporting having been prescribed psychiatric medication.

As much as some doctors appear over-sensitized to the possibility of depression, others appear to miss the symptoms all too readily. According to Mojtabai the problem, in community settings at least, seems to be one of clinical uncertainty about diagnostic criteria and "ambiguity regarding sub-threshold syndromes." This leaves us in a situation of under-diagnosis and treatment in some situations and over-diagnosis and treatment in others.

With all these diagnostic false positives and negatives would it make sense to encourage more routine screening for depression? Well no, according to the latest guidelines from Canada, effectively representing something of direction when compared with previous guidelines. The screening of adults in primary care settings, were previously recommended in cases where integrated staff systems were available to manage treatment. Now clinicians are asked to remain alert to the possibility of depression and should not apply the new guidelines in cases where patients have known depression, a history of depression or who are receiving treatment.

Why the change? Well their argument goes something like this. Although family doctors have been criticized for missing depression, many missed cases are the milder forms from which patients tend to recover without treatment. Screening, they argue, needs to be properly evaluated as to understand its effects. For example, what might the implications be if a patient is wrongly believed to have depression and then treated for it? Well, if Mojtabai's study is anything to go by, around 60 percent of the sample was being treated for depression that didn't need to be. And there is still acceptance that those who do require treatment are still being overlooked. To my mind expressing concerns over the possible 'harmful effects' of routine screening against a background of years of false or missed diagnosis appears odd, to say the least.

The U.S. Preventive Services Task Force (USPSTF) does however recommend universal screening where support exists to ensure follow-up. In the United Kingdom, a targeted approach, focusing on people with a history of depression, is recommended rather than any form of general screening. The differences may be subtle but they are differences, so why? When the USPSTF presented the findings of a systematic review into the effectiveness of screening for depression in adults it became clear that the situation is far from clear Different studies have produced divergent results and this has helped fuel the controversy surrounding the effectiveness or otherwise of screening for depression. Where does it go next? Well, the Canadian approach makes sense from a purely scientific standpoint in that further properly controlled studies are needed into the effectiveness of screening programs. However, let's not use the 'potential harm of screening' argument when the evidence already points to routine diagnostic and treatment blunders in the case of depression.


Screening for Depression in Adults. Summary of the Evidence. Article originally in Annals of Internal Medicine 2002;136(10):765-76.