New Zealanders are continuing to use more antidepressants but there is no sign it's improving mental health.

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That's the conclusion of Otago University research published in the New Zealand Medical Journal today.

New Zealand is the eighth highest consumer of antidepressants per person in the OECD.

According to the research, in 2015 13 percent of all New Zealanders aged 15 and over were prescribed antidepressants.

That was 16 percent of women and 9 percent of men, and represented a 21 percent increase since 2008.

European women aged 65 and over were the highest users, with one in five collecting a prescription.

One of the authors, psychiatrist Roger Mulder, could not say why, but said what was clear was that while antidepressants worked for some they may not work well for others.

"And one of the reasons we think this is because despite this big rise there hasn't been any evidence of community measures of mental health improving over the last couple of decades, while this has been going on.

"So suicide rates haven't gone down … it would appear people's psychological distress is at least as bad as it was."

He said those with mild symptoms did not appear to get much benefit from the drugs.

"They really work best in people with severe, recurrent or melancholic depression."

The study said the rate of increase in use had slowed, which Prof Mulder said was likely to indicate saturation, with little room for further growth in usage.

"It does bring into question our current way of trying to address psychological distress in the community, that giving more and more people antidepressants doesn't seem to be a good strategy."

An Auckland University professor of general practice and primary healthcare Bruce Arroll said antidepressants were over-rated.

"The suicide rate is stable or going up, and if they were that good it should be showing a big difference in terms of suicide rates but there's been no sign of that yet."

Mental Health Foundation chief executive Shaun Robinson said New Zealanders were too reliant on antidepressants.

"Our response to depression, anxiety and to just the general distress that people have in their daily lives is too much on that medical model. We're not offering enough counselling and therapy, we're not looking necessarily at the ... life situation of people."

Social issues needed more attention.

Warkworth GP Kate Baddock, who chairs the Medical Association, said the problem was not over-prescribing by GPs but a burgeoning mental health issue.

"We have increasing numbers of people suffering mental distress and mental stress and mental health issues, and we have a limited amount of talking therapies available which are funded."

She added antidepressants was about as effective as talk therapy and people used what was available at a reasonable cost.

Antidepressants cost the country $8.5 million in the year to June, not including GST, pharmacy mark-ups and confidential rebates.

Where to get help:

Need to Talk? Free call or text 1737 any time to speak to a trained counsellor, for any reason.

Lifeline: 0800 543 354

Suicide Crisis Helpline: 0508 828 865 / 0508 TAUTOKO (24/7). This is a service for people who may be thinking about suicide, or those who are concerned about family or friends.

Depression Helpline: 0800 111 757 (24/7)

Samaritans: 0800 726 666 (24/7)

Youthline: 0800 376 633 (24/7) or free text 234 (8am-12am), or email talk@youthline.co.nz

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Rural Support Trust Helpline: 0800 787 254

Healthline: 0800 611 116

Rainbow Youth: (09) 376 4155

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