Mental health campaigners today claimed that research indicating new-generation antidepressants work no better than dummy pills was evidence that doctors are over-prescribing.
Campaigners said millions of people with depression were not getting sufficient access to talking therapies due to GPs being over-reliant on prescribing drugs such as Prozac.
A review of clinical trials found that such drugs had no more effect than a placebo for mildly depressed patients and for most people suffering severe depression.
The study showed that even trials suggesting benefit for severely depressed people did not provide evidence of clear clinical benefit, researchers said.
A group of experts, led by Professor Irving Kirsch, from the Department of Psychology at the University of Hull, analysed 47 clinical trials using data released under Freedom of Information rules by the US Food and Drug Administration (FDA).
The researchers looked at four commonly-used antidepressants and the clinical trials submitted to gain licensing approval. They included antidepressants regularly prescribed, including fluoxetine (Prozac), venlafaxine (Efexor) and paroxetine (Seroxat).
Drug researchers
They found little evidence of benefit when analysing both unpublished and published data from the drug companies.
Furthermore, the seemingly good results for very severely depressed patients came from the fact a patient's response to the dummy pill decreased rather than any notable increase in their response to antidepressants.
"Drug-placebo differences in antidepressant efficacy increase as a function of baseline severity, but are relatively small even for severely depressed patients," the researchers said.
Dr Siobhán Barry, consultant psychiatrist and spokeswoman for the Irish Psychiatric Association, said although she welcomed the publication of the report, a number of findings of the research were "disturbing".
"It has been known for quite some time that for mild to moderate depression, various kinds of therapy are as effective as the taking of anti-depressant medication," she said.
She argued that although the State provided free drugs to all psychiatric patients, there were inadequate resources for the provision of suitable therapy. Figures for three years ago show that a quarter of the mental-health services in Ireland had no access to psychology and poor access to social work, she said.
"It's staff intensive and those staff haven't been employed."
Despite today's findings, Dr Barry warned anyone on medication that is was dangerous to stop taking it immediately without supervision and advised patients to seek medical advice on possible alternative treatments.