The development of a novel antidepressant ground to a halt this week when researchers found it did not make patients feel any better than the pills they were already taking.

The drug firms took the hit, with shares tumbling in Targacept, while AstraZeneca wrote off a total of $146.5 million for the drug’s failure.

It was bad news for investors and bad news for patients - and a depressingly familiar tale for drugmakers seeking to develop new treatments for brain illnesses.

Data from Thomson Reuters Pharma shows returns for pharmaceutical companies in the antidepressant market are collapsing - despite widespread use of pills like Prozac - as patents expire and new drugs fail to make it to market.

Some Big Pharma firms are quitting the field altogether. Others are hacking back investment and shedding jobs.

These might seem like prudent decisions in an increasingly expensive and frustrating field. Other diseases such as cancer and diabetes are reckoned to be better areas to be in these days. Yet some scientists say the timing could hardly be worse.

Researchers who study the brain believe they are finally figuring out the basic mechanics of depression and other mental disorders, discoveries that should open the door to far more effective ways to tackle illnesses that can cripple society.

“It’s a great time for brain science, but at the same time a poor time for drug discovery for brain disorders,” says David Nutt, professor of neuropsychopharmacology at Imperial College London. “That’s an amazing paradox which we need to do something about.”

HIGHEST BURDEN

The numbers say it all.

Major depression affects around 20 percent of people at some point in their lives. The World Health Organization predicts that by 2020, depression will rival heart disease as the health disorder with the highest disease burden in the world.

Around a third of all Americans and 40 percent of all Europeans could be classified as mentally ill, with a European study last year finding that almost 165 million people in the region suffer each year from a brain disorder of some kind.

The study covered more than 100 illnesses from insomnia through depression to schizophrenia.

In the developed world, at least, we are popping more pills than ever. One in five adults in the United States is now taking at least one psychiatric drug, according to data from Medco Health Solutions, a pharmacy benefit manager.

But the drugs only work in some of the people some of the time, and there is an urgent need for new, more effective therapies.

“The burden of these diseases is huge, and the costs are enormous - and it’s only going to get worse with increasing life expectancy,” said Colin Blakemore, professor of Neuroscience at Britain’s Oxford University.

It is a human tragedy that should, in theory, also be a major market opportunity for drugmakers. The problem is that realizing the potential gains is proving extremely hard.