text: The belief that the most popular antidepressant drugs raise serotonin levels in the brain is nothing more than a myth, a leading professor of psychiatry has claimed. David Healy, head of psychiatry at the Hergest psychiatric unit in Bangor, North Wales, said the misconception that low levels of serotonin were responsible for depression had become established fact. He suggested that the success of so-called SSRI drugs – which include Prozac and Seroxat – was based on the ‘marketing of a myth’. Scroll down for video . The idea that the most popular antidepressant drugs raise serotonin levels in the brain is nothing more than a myth, psychiatrist Professor David Healy argues. Pictured is Prozac, one commonly prescribed  SSRI . The emergence of these serotonin reuptake inhibiting (SSRI) drugs in the late 1980s came after concerns about tranquilliser use to treat depression. Even though they were weaker than old-style tricyclic antidepressants, they took off because of the idea that SSRIs restored serotonin levels to normal, ‘a notion that later transmuted into the idea that they remedied a chemical imbalance’. In an editorial in the BMJ, Professor Healy said that in the 1990s, no one knew if SSRIs raised or lowered serotonin levels but there was no evidence that treatment corrected anything. He said: ‘For doctors it provided an easy short hand for communication with patients. ‘For patients, the idea of correcting an abnormality has a moral force that can be expected to overcome the scruples some might have had about taking a tranquilliser, especially when packaged in the appealing form that distress is not a weakness.’ However, other psychiatrists have refuted the professor’s claims, saying the profession has moved on from a simplistic description of the pills correcting a chemical imbalance. They warned the controversy might harm depressed patients if they were deterred from taking the drugs, which had been proved to work in trials and the ‘real world’. Depression should be re-defined as an infectious disease rather than an emotional disorder, argues one scientist. The condition could result from a parasitic, bacterial or viral infection and future research into the condition should search for these micro-organisms, argues Dr. Turhan Canli, of Stony Brook University, U.S. If his theory is true, he hopes a vaccination to protect against depression could be developed in future. Writing in the journal Biology of Mood and Anxiety Disorders, Dr Canli said: 'It is time for an entirely different approach. 'Instead of conceptualising major depression as an emotional disorder, I suggest to re-conceptualise it as some form of an infectious disease. 'I propose that future research should conduct a concerted search for parasites, bacteria, or viruses that may play a causal role in the etiology of major depression.' Professor Sir Simon Wessely, President of the Royal College of Psychiatrists, said: ‘That antidepressants are helpful in depression, together with psychological treatments, is established. How they do this is not. ‘Most researchers have long since moved on from the old serotonin model. ‘Most important of all, SSRIs are safer if taken in overdose than the older tricyclics. ‘People should not change their current medication on the basis of this editorial alone.’ NHS Choices, the website which advises patients, says: ‘It would be too simplistic to say that depression and related mental health conditions are caused by low serotonin levels, but a rise in serotonin levels can improve symptoms.’ Professor Healy’s editorial says it is important to raise questions about the drugs. He said: ‘In other areas of life the products we use, from computers to microwaves, improve year on year, but this is not the case for medicines, where this year’s treatments may achieve blockbuster sales despite being less effective and less safe than yesterday’s models. ‘The emerging sciences of the brain offer enormous scope to deploy any amount of neurobabble. 'We need to understand the language we use. Until then, so long, and thanks for all the serotonin’, he concludes. Professor David Taylor, Director of Pharmacy and Pathology and Head of Pharmaceutical Sciences Clinical Academic Group, King’s Health Partners, South London and Maudsley NHS Foundation Trust, said: ‘Professor Healy makes a forceful but poorly supported argument against something which doesn’t and has never really existed: the idea that SSRIs ‘correct’ an ‘imbalance’ of serotonin in the brain. ‘Researchers and psychiatrists alike know that SSRIs are effective in a number of disorders but no one is sure exactly how they work. Their readily demonstrable effect is on serotonin but they have many indirect secondary effects in the brain. Other psychiatrists warned the controversy might harm depressed patients if they were deterred from taking the drugs, which had been proved to work in trials and the ‘real world’ ‘Prof Healy fails to mention that SSRIs supplanted earlier tricyclics largely because of their relative safety in overdose, not because of any conspiracy concerning a theory of serotonin’s involvement in depression.’ Dr Paul Keedwell, Consultant Psychiatrist and Specialist in Mood Disorders, said: ‘In the real world of the clinic, SSRIs are undeniably effective in treating individuals with major depression. 'They have become the first line treatment of choice because they have fewer troublesome side-effects than their predecessors, and are safer in overdose. ‘David Healy has previously claimed that SSRIs cause dependence or provoke suicide. ‘In so doing he has risked deterring individuals with severe depression from getting the help they need and this latest article just adds to this problem. ‘The risk of suicide from untreated depression is much greater than the risk of treating it with antidepressants, and yes, this includes SSRIs.’
target: David Healy is head of psychiatry at the Hergest psychiatry unit in Bangor .
  Claims the idea low levels of serotonin causes depression is a fallacy .
  Marketing of SSRI drugs like Prozac has been 'based on a myth', he claims .
  Experts refute his claims saying 'SSRIs work in the real world of the clinic'