"Ratatatat...ratatatat" -- the loud banging noise in Professor Thomas Schläpfer's laboratory at the University of Bonn does not sound too different from that of a pneumatic drill or possibly a machine gun.

Either way, the sound that emanates from what looks a bit like a fridge is unlikely to evoke a feeling of comfort or calm in anyone listening to it the first time. Yet this machine may hold the key in the search for new ways of treating people suffering from depression.

The procedure is called "Transcranial Magnetic Stimulation," or TMS. And it could be used to treat patients who don't respond to traditional forms of therapy, which commonly involve a combination of psycho-therapy and medication.

It is thought that patients might respond to a therapy which goes deeper into the brain to stimulate it. TMS is just such a therapy. This non-invasive method works by creating a very strong magnetic field which stimulates different regions of the brain.

Brainchemistry out of balance

Scientists still don't know exactly what is wrong in the brain of people who suffer from mental illnesses. They suspect that some kind of chemical imbalance is involved which may result in higher activity in some parts of the brain while it may be less than normal in others. The idea is to stimulate the latter in an attempt to redress the balance in activity levels.

A part of the brain called the limbic system is of particular interest to Professor Schläpfer.

"It is responsible for the mediation of mood effects in the brain," he said. "One very important region is the dorsolateral prefrontal cortex."

In people with depression, this region is less active than in healthy individuals.

"We know that if we have effects on this region we can treat the bad effects of major depression," Schläpfer said.

For treatment a butterfly-shaped coil attached to the machine is held close to the patient's head, where it administers the magnetic stimuli -- two second-long trains of short impulses during intervals of about 30 seconds. The whole procedure lasts about half an hour. During treatment the patients are sitting in a chair and are usually awake. The only thing they feel is their muscles twitching, which is not painful. Some say they can feel something going on in their brain. But Thomas Schläpfer can't yet say for sure whether the sensation is real or just a placebo effect.

Other therapies to stimulate the brain

There are other and older methods for stimulating the brain. One of these is electro-convulsive therapy. It involves inducing a seizure in the brain, using an electric current. This is an accepted method in extreme cases. But there are some negative side effects.

"It has long been known that electro-convulsive therapy has at least transient effects on the memory," said Michael Wagner, a psychiatrist. TMS in comparison performs much better.

"Transcranial magnetic stimulation had no effect or even improved the memory," Wagner said.

However, as psychiatrists at the University of Munich report, TMS may have other side effects and possibly increase the risk of epileptic fits. As yet it's not clear exactly how long the positive effects achieved with TMS last beyond treatment. According to the scientists from the University of Munich the effect subsides within only a few days or weeks after treatment is discontinued. However, the situation improves significantly if patients are put on medication during and after TMS treatment, the scientists say.

A step forward in the fight against a severe disorder

That's why TMS looks like a step in the right direction. Professor Schäpfner and his team at Bonn have already started to improve the method. They believe that TMS could be used to even induce therapeutic seizures using TMC. These could be more effective than the basic form of transcranial magnetic stimulation and have fewer side effects than traditional electroconvulsive therapy.

Thomas Schläpfer said the search for new treatments must go on.

"Major depression is a very severe and potentially deadly disorder. 18 percent of the patients die, mainly through suicide," he said. "They are not able to experience joy anymore. They cannot work any more and lose their family, their social functions."

TMS is still very new and not yet widely used. But already about 20 groups worldwide are engaged in research on TMS and the researchers hope that the new treatment could soon help many people beat depression.