He has examined worldwide studies linking proximity of masts to depression. Dr Coghill’s work is likely to trigger alarm and lead to closer scrutiny of the safety of masts, which are frequently sited on public buildings such as schools and hospitals.

It is also likely to fuel more campaigns against placing masts close to public places on health grounds.

They include Kelly Stephenson, 20, who hanged herself from a shower rail in February this year while on holiday in Folkestone, Kent.

Dr Coghill said: “There is a body of research that has over the years pointed to the fact that exposure to mobile radiation can lead to depression. There is evidence of higher suicide rates where people live near any electrical equipment that gives off radio or electrical waves.”

The national average for proximity to a mobile phone transmitter varies depending on the type of mast. The latest masts are far more powerful so they can transmit more sophisticated data, such as photos and videos for people to download on internet phones.

The national average distance from a new powerful mast is a kilometre while in Bridgend it is 540 metres. Three transmitters were within 200 metres, 13 within 400 metres and as many as 22 within 500 metres of victims’ homes. Carwyn Jones, 28, who hanged himself last week, was the third young person in his street to commit suicide.

Dr Coghill added: “What seems to be happening is that the electrical energy is having an effect on the chemistry of the brain, depleting serotonin levels. We know that in depression serotonin levels are low and that a standard treatment for depression is to give drugs to boost serotonin levels. As they begin to work, the patient’s depression lifts.”

Since January 5, 2007, there have been 22 deaths of young people in the Bridgend area. Some believe the suicides are linked but so far experts have failed to find a common cause.

Thomas Davies, 20, hanged himself in February 2007. Last night his brother Nathan, 19, welcomed Dr Coghill’s research. “As far as this family is concerned nothing can bring Tom back,” he said. “But if there is a link found and something can be done then it could prevent further suicides.”

The Government’s Health Protection Agency insisted that fields from mobile masts – even modern powerful masts – were well within international agreed safety limits. “There is no evidence that masts do you harm. The levels of radio waves are very low.”