A leading Australian psychiatrist has stirred up the debate on depression, saying many people could be diagnosed with clinical depression who are just feeling a bit blue.
But there is an argument that such people should be treated anyway because they are at risk and could go on to develop major depression.
The debate has been aired today in the British Medical Journal.
Professor Gordon Parker of the University of New South Wales says depression is being over-diagnosed.
"My personal view is that it is normal for humans to become depressed," he said.
"We can call that normal depression and there's also clinical depression."
He says while 20 to 30 years ago clinical depression was diagnosed in about 5 to 10 per cent of the population, current diagnostic criteria would cover up to 90 per cent of the population.
"To my mind that strains credibility," Professor Parker said, director of the mood disorders centre, the Black Dog Institute.
Professor Parker says criteria introduced in the 1980s broadened the definition of depression to include minor, every day conditions.
"Clinical depression in the old days was black melancholia," he said.
"Now we've got blue becoming the new black."
Current system saves lives
But Professor Ian Hickie of the University of Sydney rejects the idea that current diagnosis of depression is over-inclusive.
"Against what criteria is it over-inclusive? What's the benchmark?" he said.
Professor Hickie, a past chief executive of the national depression initiative Beyondblue, says the more people that are picked up by the criteria the better.
He says people with lesser forms of depression are more likely to be at risk from premature death than the general population, and to develop major depression later on.
"The increased treatment rate is a Godsend," he said.
Professor Hickie says just as treating less severe forms of hypertension helps save lives, so does treating less severe forms of depression.
"This is where cardiology was 30 years ago," he said.
He disagrees with Professor Parker's estimate that the current criteria would cover around 90 per cent of the population, citing instead his "best guess" as 50 per cent.
But he says the argument is "completely sterile" because there is evidence that the current approach to diagnosing and treating depression has saved lives.
"What we see is that when treatments have gone up suicide has gone down," he said.
Professor Hickie also argues that a broader diagnosis has reduced the stigma of being "depressed", forcing the abandonment of old demeaning labels of "stress" and "nervous breakdown" that stopped people from seeking help.
Still, he says, only half of those in the community who fit the criteria for major depression are receiving treatment and that more should be treated.
Professor Parker supports greater awareness and less stigmatisation of depression but he says the downside of such inclusive diagnostic criteria is that some people are being treated when they don't need to be.
He is also concerned that the current diagnostic criteria are too "dumbed down" and make it difficult for clinicians to diagnose the cause of the depression and select the best treatment.
Professor Parker thinks many people are being treated with drugs who should be treated with other more effective means, and vice versa.
He also wants to educate the public and practitioners about an alternative model that focuses on identifying the driver of a person's depression to determine the best treatment.
"It's a much more 'horses for courses' model," he said.
"Sometimes it will be a drug, sometimes it will be psychotherapy, sometimes it will be CBT [cognitive behavioural therapy] or counselling and sometimes it will be commonsense support."
But Professor Hickie says Professor Parker's model assumes the causes of depression are known and can be used to deduce the best treatment.
He says there is no consensus on the causes of depression, which means clinicians can only use their judgment about what works to determine the treatments they provide.
Professor Parker acknowledges his is a minority position but says support for it is increasing.