The treatment - injections into the penis to produce an erection - might cause long-term damage to the complex mechanisms involved, according to Dr John Bancroft, a psychiatrist who heads the Medical Research Council's Behaviour Research Group in its Edinburgh Reproductive Biology Unit.
Speaking at the British Psychological Society's annual conference in Blackpool, he warned against the 'medicalisation of the penis', with men promised one easy solution to their problems in getting or maintaining an erection.
His research has found that if a man has a psychological problem this can prevent even the injections from working.
Claims of a 90 per cent cure had become commonplace, he said.
'Many men are more than ready to part with their money in the hope of getting their erections back.
'There is therefore scope for exploitation. Doctors, in particular urological surgeons, are now taking a very much greater interest in this problem, particularly in the private sector.'
He said that over ten or 12 years there had been a complete swing from the belief that 90 per cent of impotence had a psychological cause, to doctors claiming that the majority of cases had a physical cause. Neither belief had been conclusively tested, he said.
The most popular treatment involves the injections, which men are taught to do for themselves whenever they wanted to have sex. Occasionally these go wrong and the man is unable to lose his erection for many hours. Dr Bancroft said this could cause damage to the delicate structures of erectile tissue.
The injections of prostaglandin or a drug called papaverine relax smooth muscle tissue in the penis to produce an erection. Dr Bancroft said that erectile tissue was sponge-like, made of little sacs or spaces, through which blood flows. The walls of these sacs are lined with smooth muscle. Usually this muscle is contracted, keeping the spaces small and narrow. When they relax in response to sexual stimulus or an injection, the spaces enlarge and fill with blood, producing an erection.
In his study of 160 middle-aged men with what Dr Bancroft calls erectile dysfunction, he found that half had a psychological cause. One method he uses is to measure night-time erections during sleep, in which the men attach a monitoring device to the penis before they go to bed.
'Men who are functioning well will have several erections during sleep, often waking with one. If there are erections then we know there is nothing physically wrong so we should look for another cause,' he said.
Psychological causes were various, but could involve resentment or insecurity in a relationship or loss of confidence in sexual performance. He said that erectile dysfunction was a truly psychosomatic disorder with psychological problems often causing a physical difficulty.
'It is not helpful to reinforce the idea that making love is a purely physical process. We need to understand much more about how the psychological and physical processes interact,' he said.
Dr Bancroft acknowledged the help that physical medicine had been in understanding the processes better and devising series of diagnostic tests. But he said mind and body interactions had now to be understood in seeking the cure for impotence. In the meantime he advised men seeking help to look for clinics where there were psychologists as well as specialists in physical medicine.