It is hoped new research will help to convince both doctors and patients not to rely so heavily on drugs to treat depression.

Researchers from Auckland Medical School have found anti-depressant drugs only seem to benefit around 10 to 15 percent of users and the placebo effect is more likely to be behind patients getting better.

Dr Bruce Arroll says of their entire research group, 65 percent of people got better when taking an anti-depressant - and most were in the placebo group. He believes the placebo effect is anywhere between 30 percent to 65 percent and says there is some thought that it has been rising since the 1970s.

Dr Arroll says because the drugs are called anti-depressants, people expect them to make them better. He hopes the findings will mean doctors and patients look at more rational treatment options, like lifestyle changes and developing things like gratitude diaries.

Dr Arroll says anti-depressant drugs are still helpful for some people, but something as simple as exercise is also a good first step towards recovery.