Therapy delivered via the internet is just as good as face-to-face sessions for treating depression, say Swedish researchers.
Some people may benefit from web-based advice
Web-based programmes could help counteract the current shortage of skilled therapists, they say.
Cognitive behavioural therapy, the focus of the study, helps a person to change how they think and what they do to improve state of mind.
The research is published in the British Journal of Psychiatry.
In the study, 117 volunteers with mild to moderate depression participated in either a web-based self-help CBT programme plus an internet discussion group, or an internet discussion group alone.
The do-it-yourself CBT programme consisted of 89 pages of text divided into five modules that were estimated to take eight weeks to complete.
Overall, 37% of the patients withdrew from the programme - the main reason given was that it was "too demanding".
However, those that continued with the programme reported significant improvements to their psychological wellbeing.
The success of the web-based self-help programme was the same as that seen in past studies of face-to-face therapy, and was much more effective than the internet group therapy on its own.
The self-help programme resulted in decreased depressive symptoms immediately after treatment and at the six-month follow-up, the researchers found.
Lead researcher Professor Gerhard Andersson, from Linköping University, said: "Benefits were also observed regarding anxiety symptoms and quality of life.
"Self-help treatment of depression is an attractive treatment option."
He said such internet-based therapy options should be pursued further as a complement or alternative to conventional treatment methods.
Dr Peter Haywood, consultant clinical psychologist at the South London and Maudsley NHS Trust said: "Self-help materials can be extremely helpful. Obviously it will not work for everybody.
"There is a shortage of trained CBT therapists so this self-help approach might be useful for some people.
"There are some very well established self-help books that many people have found beneficial, so there are all kinds of ways self-help can be made available."
Richard Brook, chief executive of Mind, said: "Computer-delivered CBT is an important addition to the range of treatment options available for people experiencing depression.
"This method of delivery is useful for people who might not be able to access CBT easily because of their remote location, or for people who find it difficult to speak 'one-to-one' about their depression.
"With the current shortage of therapists, people can sometimes wait up to a year for treatment on the NHS.
"However, online CBT will not suit everyone. It should not be used as a reason to evade training enough therapists so that people experiencing mental health problems can access the treatments they need when they need them."