A landmark study has found that antidepressants are effective and more people should take them.
The research, published in The Lancet, also identified the most and least effective antidepressants available worldwide and on the NHS.
Researchers from Oxford University analysed data from 522 separate trials involving 116,000 patients suffering from moderate to severe depression.
Each of the medicines performed significantly better than a placebo – some by more than others.
Fluoxetine, sold under the brand name Prozac is among the best known pills for counteracting depression. It was prescribed 6.6m times by the NHS in 2016.
However, it was only the 16th best performing medicine of the 21 most common brands on offer – 52% more effective than a placebo.
At the top of the rankings was Amitriptyline, which performed 113% better than a course of placebos.
The drug was discovered in the 1950s, and is also used for migraine and chronic pain relief. It is a respiratory depressant and can cause overdose.
Researchers sought to use the findings to overcome "ideological" opposition to the treatment of depression with drugs.
"Taking antidepressants is frequently portrayed as a negative thing or something done only when other therapies are not available or have failed," said Helen Stokes-Lampard, chairwoman of the Royal College of GPs.
"This research should reassure patients who are taking or are contemplating commencing antidepressants, and the doctors that prescribe them, that they are an effective treatment."
John Geddes, one of the reports authors, said: "There's something about taking a drug for a mental health problem that people think, 'That's not what I want to do', so it's important to be clear about the efficacy.
"We do tend to be a bit squeamish about it . . . If it was cancer and only one in six were getting access to effective treatment we'd think there was something squiffy going on."