The Canadian Task Force on Preventive Health Care issued the updated guideline Monday, saying there is little evidence in the medical literature to support routine screening of all patients and suggesting it could do harm in some cases.
Dr. Michel Joffres, chair of the task force's depression guideline working group, said mass screening could lead to patients feeling stigmatized or labelled and some being misdiagnosed and unnecessarily treated.
"The way that we define screening is in people we know do not have a history of depression, they have not been treated for depression and they have no apparent signs or symptoms of depression," Joffres said from Victoria, where he is a professor of health sciences at Simon Fraser University.
Screening involves asking patients questions — such screening tools can range from two to 30 queries — about their emotional state and physical signs that might indicate depression. It is not the same as diagnosis, which would involve a deeper probe.
The task force, which last issued guidelines on depression screening in 2005, reviewed worldwide studies on whether there is a benefit to screening patients at average risk for depression and found there is little evidence one way or another.
"There is a lack of high-quality research demonstrating the benefits and harms of screening in adults with no apparent symptoms of depression," said Joffres.
"Without evidence that screening is beneficial for patients with no apparent symptoms of depression, and considering the potential harms, we recommend not to routinely screen for depression in primary-care settings — either in patients at average risk, or those with characteristics that may increase their risk for depression."
The guideline is published in this week's Canadian Medical Association Journal. It is accompanied by a commentary which lauds the task force recommendation written by Roger Bland of the University of Alberta and David Streiner of McMaster University in Hamilton.
Bland, professor emeritus in the department of psychiatry, said routine screening turns up more false-positives than truly positive indications of depression. With one standard screening tool — called the Kessler Psychological Distress Scale, or K10 — 73 per cent of all positives would in fact be false-positives, he said.
"I think increasing awareness and asking questions where you have a suspicion is probably likely to be the best approach at this time," Bland said Monday from Edmonton.
Joffres said family doctors should still be alert for signs of depression, especially among patients at higher risk for the mental health condition. That includes patients with a history of depression and those belonging to groups in which depression occurs more often, such as the elderly and economically disadvantaged.
"They should be alert to the clinical clues of depression, such as depressed mood and diminished interest in pleasure, insomnia, an inability to think and concentrate, and thoughts of death," he said.
"So those are clues that may indicate then that 'Oh, I need to pursue that.'"
Dr. Garey Mazowita, a spokesman for the College of Family Physicians of Canada, called the new guideline "an awfully big paint brush for a fairly nuanced intervention."
Mazowita said task force members acknowledge in their article that high-quality research needs to be done to address whether routine screening is actually beneficial, and that their recommendation against the practice is classified as "weak."
He believes most family doctors will continue to screen patients, especially those considered to have an elevated risk of depression because they belong to a certain population — the elderly dealing with chronic diseases or social isolation, or economically vulnerable inner-city residents, for example.
"I think the higher the prevalence in one's practice, the more sense a screening tool makes," said Mazowita, head of family and community medicine at St. Paul's Hospital in Vancouver.
Using a screening tool to raise the issue of depression also helps to reduce the stigma long associated with mental health disorders, which some patients may be reluctant to broach with their doctor out of embarrassment or fear of wasting the physician's time on non-physical problems, he said.
What's more, primary care itself is undergoing a change in many parts of Canada, going beyond family doctors working alone to team-based practices with a range of allied specialists to provide expert diagnosis and treatment to patients.
With primary care in the process of reinvention, the article shouldn't be seen as a signal to care providers to "walk away en masse from screening," Mazowita said.
"It's all about access, openness, permission to talk, being non-judgmental. It's working with others and being able to access other resources when you uncover something that perhaps you may not have the expertise or time to deal with yourself."
Mazowita said the idea shouldn't be to discourage conversation about mental health problems or efforts to uncover their possible existence in a patient, "whether it makes sense from a purely scientific perspective or not."
"As a society, we need to normalize these discussions about mental health — and screening is one way to do that."
Joffres said that if individual family doctors believe it's important to screen for depression and their patients are not concerned about potential harms, certainly they can go ahead and screen. "We're not saying absolutely 'do not it,'" he said.
"The task force places a high value on clear evidence — and we don't have it."