Prescribing self-help books on the NHS is an effective treatment for depression, a study suggests.
Patients offered books, plus sessions guiding them in how to use them, had lower levels of depression a year later than those offered usual GP care.
The effect was seen in addition to the benefits of other treatments such as antidepressants, Scottish researchers report in the journal Plos One.
Such an approach may help the NHS tackle demand for therapy, they said.
More than 200 patients who had been diagnosed with depression by their GP took part in the study, half of whom were also on antidepressant drugs.
Some were provided with a self-help guide dealing with different aspects of depression, such as being assertive or overcoming sleep problems.
Patients also had three sessions with an adviser who helped them get the most out of the books and plan what changes to make.
After four months those who had been prescribed the self-help books had significantly lower levels of depression than those who received usual GP care.
A year later, those in the self-help group were more likely to be keeping on top of their depression.
Study leader Prof Christopher Williams, from the University of Glasgow, who also wrote the books called Overcoming Depression and Low Mood, said the guided sessions were the key to getting people engaged.
The sessions can be delivered in general practice without referral to a specialist, taking pressure off waiting lists.
In Scotland, a telephone support service has now been set up to help support those using the books, which can be freely copied and disseminated, he added.
"We found this had a really significant clinical impact and the findings are very encouraging," he said.
"Depression saps people's motivation and makes it hard to believe change is possible."
The challenge for the NHS, where self-help books are already used in many places, is how to implement this model so people have easy supported access in primary care, he said.
'Worth investing in'
There has been huge investment in better treatment for depression in the UK in recent years with the Improving Access to Psychological Therapies programme in England set up to widen access.
It has been estimated this approach could save the NHS up to £272m and the wider public sector £700m.
But, says Prof Williams, despite the huge levels of investment, it is just not possible to refer everyone with depression to mental health services.
Dr Paul Blenkiron, consultant in adult psychiatry at Leeds and York Partnership NHS Foundation Trust, said the results showed that guided self-help is effective and is "something the NHS should be investing in".
He is currently advising on behalf of the Royal College of Psychiatrists, on a National Books On Prescription Scheme, to be rolled out across UK public libraries this year.
Thirty books, including the one used in the study, have been selected.
But Dr Blenkiron said self-help would not be suitable for everyone: "The key thing is that the person is committed to doing some work."