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Tens of thousands of New Zealanders are swallowing antidepressant pills that don't work, according to a new study.
The study - one of the largest into popular drugs - found the pills have no ‘‘clinically significant'' effect.
The results showed that the drugs increased patients' scores on a 51-point depression scale by an average of only two points, although the study reported the drugs had a more significant effect on patients with severe depression.
It suggested ‘‘talking treatments'' should replace drug treatments for clinically depressed people.
The drugs were prescribed more than 700,000 times in New Zealand last year at a cost of almost $28 million.
The medical director of drug-buying agency Pharmac, Dr Peter Moodie, said the study included ‘‘some very interesting data'', and would be discussed by the agency's clinical committees.
But Pharmac would not rush a decision on the findings. The drugs in the study are a modern type of antidepressant called selective serotonin re-uptake inhibitors (SSRI).
The most widely used antidepressants in New Zealand are Fluox (formerly known as Prozac) and Loxamine.
The study was led by the University of Hull in England, and published in the Public Library of Science, an online journal.
Auckland University Professor of Health Psychology Keith Petrie said the study had been properly done, and its findings were important.
But he cautioned against applying averaged results to individual cases. The study did report excellent results for some patients, he said.
A Ministry of Health spokeswoman said the ministry did not plan to change advice it gave on depression treatment as a result of the review.
‘‘The ministry would like to reassure those who are taking these drugs that they can be very helpful.''
The recently-retired chairman of the New Zealand national committee of the Royal Australia New Zealand College of Psychiatrists, Dr Allen Fraser, said the drugs were badly represented by the study.
Less than 10% of patients were deemed suitable for trials, and the trials lasted less than six weeks.
Treatment for depression usually lasted at least six months, and patients generally showed steady improvement throughout that time.
There were valid grounds for suggesting less severely depressed people have non-medicated treatment initially, he said.