According to new research from Britain, new generation anti-depressants could be for many patients a waste of time and money and offer little clinical benefit.
Scientists from Hull University carried out an analysis of a 47 clinical trials involving five thousand patients with depression and found that most widely-prescribed anti-depressants work little better than dummy pills.
The antidepressants - Selective Serotonin Reuptake Inhibitors (SSRI) - which were studied included Prozac, Seroxat and Efexor and were found to be little more effective than placebos in improving the mental health in the majority of cases.
The new research found that the most widely prescribed anti-depressant pills are ineffective and only in the most extreme cases of depression did the tablets prove substantially superior in improving mental health.
Lead researcher Professor Irving Kirsch says the difference in improvement between patients taking placebos and patients taking anti-depressants is not very great, which means that depressed people can improve without chemical treatments.
Antidepressants are taken by around two million Britons and have been linked to a host of side effects including suicide, suicidal thoughts, self harm, anxiety, insomnia, nausea, headaches and vomiting.
Some experts have described the results as "fantastically important".
The study has credibility because it has included data which drug companies had chosen not to publicise possibly because it was less favourable than they would like, and it suggests that millions are needlessly taking powerful and potentially dangerous drugs.
Seroxat alone has been linked to at least 50 suicides in both adults and children in the UK since 1990.
The research is timely as it comes as prescriptions for anti-depressants have reached record levels, with 31 million written in 2006 at a cost to Britain's NHS of almost £300million, around half of these were for Prozac, Seroxat, Efexor and other SSRIs.
Researcher Professor Irving Kirsch says the data suggests there is little evidence to support the prescription of anti-depressant medication to any but the most severely depressed patients, unless alternative treatments have failed to provide benefit.
The data on Prozac, Seroxat, Efexor and a fourth drug not used in the UK had been submitted to the U.S. drug watchdog ahead of the antidepressants being licensed for sale.
Of those taking part in the studies two-thirds were prescribed the SSRIs, while the remainder took placebo tablets.
A comparison of the two groups showed that in the majority of cases the mental health of those taking anti-depressants improved little more than those on the placebos, and only those who were severely depressed (a very small proportion of those studied) improved substantially on the medication.