Professor Arthur Kleinman of Harvard Medical School said the World Health Organization (WHO) estimated that depression would be the second leading cause of death in the world by 2020.

As 80% of the world's population lived in developing countries, the problem was going to be greatest there, he told a London conference on depression, co-sponsored by theWHO.

"It is a vast problem of resources," he stated. "In the West, we are debating whether patients should be treated in primary care or by psychiatrists.

"But in developing countries, only a select group in the capitals see psychiatrists. People in rural areas do not even see a general practitioner. They mostly see a nurse.

"It is in that setting that we need to think about depression."

Priority

Professor Kleinman said it was time for experts to put pressure on governments to ensure mental health was given a bigger priority in developing countries' health programmes.

He called for better evaluation of mental health programmes, saying many were effective, but were discontinued because there was no data to back them up.

"We have enough information about how to treat people who are depressed. It is time to intervene."

He added that many people in developing countries self-medicated, buying depression treatments on the black market or elsewhere.

This meant they often took inadequate dosages or mixed drugs inappropriately, provoking an adverse reaction.

He said that last year 200,000 people in China died as a result of misuse of medication.

He added that there was evidence that mass marketing of drugs and drug information to the public was also leading to self-medication in the West.

Professor Kleinman said research on depression was vastly biased towards the West. He estimated that 90% of data about depression was based on studies on people from North America or Europe.

Data from China, for example, suggested that suicide and depression were not necessarily linked.

He said there was also a clear link between social problems and depression, but there was a refusal by many to recognise this relationship among many in the US, where most research still concentrated on the biological aspect of depression.

This was possibly because social problems were not seen as 'real', compared with biological/medical problems.

Over-diagnosis

In developing countries, there was a problem with under-recognition of depression, but in the West there was a danger of over-diagnosis, said Professor Kleinman.

"There is a tendency to call all sadness depression and prescribe drugs in ways the research has not indicated because it has been tested on the clinically depressed," he stated.