In his new book, A Piece of My Mind, he is critical of this model, instead preferring what is called the 'subtyping model', which argues there are meaningful subtypes of mood disorders that benefit from quite differing treatments.
One of the major obstacles, with depression for example, is diagnosis, he says.
Prof Parker uses the analogy of a woman who has a breast lump being told whether it is a large or small one, as opposed to the more detailed diagnosis of whether it is cancerous or a benign cyst.
A diagnosis such as 'major depression' is non-specific, he says.
In countries that operate with the 'dimensional model', people get treatment that is largely a consequence of the practitioner's training or professional discipline, Prof Parker says, as opposed to being a more thorough examination of the individual in question.
In other words, sufferers are being fitted to the background training of the practitioner, whether they be a GP or psychiatrist etc, rather than having the treatment fitted to the actual cause of the disorder.
"...I see people coming in with rip-roaring melancholia (a form of depression) where they're just unable to fire up to work and somebody's been giving them psychotherapy for years when they need medication.
"And conversely I see many examples where people do not need medication... and they get a remorseless parade of medications and then because they don't respond... they're labelled treatment-resistant."
Prof Parker, the founding director of the Black Dog Institute, says it's a problem that needs to be addressed, or at the least, discussed.
"My passion and my concerns lie in what I believe to be a reality that about 80 per cent of people with a mood disorder can have (it) brought under complete control or very good control with appropriate management.
"That is a very high yield in psychiatry and it would be a very high yield in medicine and yet that is the potential.
"Where I get stirred every week of my professional life is where I see diagnostic and management problems and where that figure will never be approached by those who operate to a lower level of clinical skills."
The solution to these problems, Prof Parker says, is to go back to the past and specify the meaningful mood disorders (ie. bipolar I, bipolar II, melancholia etc), work out how best they can be diagnosed, and then identify their specific treatments, "because they do need quite differing treatment".
Although education at university level is important, Prof Parker believes health practitioners currently in the field should be targeted as a priority.
"The most difficult group to change is psychiatrists because they've been indoctrinated in the DSM (the American Psychiatric Association's Diagnostic and Statistical Manual) model... a very simplistic model, the consequences of which continue to appal me.
"We see lots of people get a diagnosis of 'major depression' and it turns out they've got sleep apnoea or ADHD or merely have a transient stress-based reactive state.
Prof Parker, who has been a psychiatrist for more than 40 years, describes psychiatry as a "cookbook recipe of focusing on generalities and not on the particulars".
Part of the problem, he adds, is that practitioners are encouraged to see depression as a disease and therefore needing anti-depressant drugs.
"Psychologists have designed themselves as a profession that does not use drugs, and for a long period they wouldn't treat a patient on medication, and clinical psychologists have one big arrow in their bow and that is Cognitive Behaviour Therapy (CBT).
"They are told that (CBT) is the dominant treatment, evidence-based, evidence-supported, has a high credibility, and they are trained in that as their speciality.
"So everyone that walks through a modern clinical psychologist's door is almost certainly going to get CBT, whatever (disorder) they walk in with. So this is a bizarre model."
Another step forward would be educating mood disorder sufferers. If they are aware there are a number of treatment options then they too may ask more questions, consult different practitioners and research their conditions online at websites such as that of the Black Dog Institute.
Prof Parker, who recently stepped down as executive director of the Institute, says there is rich educational material on the site about differing depressive disorders as well as a self test for bipolar disorder.
"We get over 30,000 people per month do that self test and we've actually evaluated and what we've found is that people who get the presumptive diagnosis... the people who go off and have it checked, get it confirmed, and have their treatment modified, do superbly better than the others."
Prof Parker, who is a Scientia Professor of Psychiatry at the University of NSW, wants the 'subtyping model' to be exposed Australia-wide to anyone working in the mental health field. He hopes practitioners and the public are made aware that there is another potential model that may be far more productive than the current.
On top of misdiagnosis and poor management, the other issue within the field of mental health is patients going undiagnosed.
Although Prof Parker says it is less of a problem now than it has been in the past, he continues to meet people who have been seeing a health professional weekly for 10-odd years and still don't have a diagnosis or treatment plan.
He refers again to the breast lump analogy.
"If you went to see a surgeon saying, 'I've got this breast lump', what would you want? You would want a diagnosis as fast as possible and a plan for action.
"I don't see why mood disorder management should be any different and I'm appalled at times by hearing of patients having to wait three months to see somebody and then never getting a specific diagnosis and just having conversations week after week."
- AAP
