Is it steroids or an overdose of vanity that turns bodybuilders into dangerous men?

The Home Office's decision last month to outlaw the sale of anabolic steroids has been called into question by government-sponsored research which concludes that the drugs do not cause violent behaviour.

The two-year study found that acts of violence carried out by steroid users were more likely to be prompted by the insecure, selfish and narcissistic personalities of individual bodybuilders than by the drugs.

Researchers from Manchester University and the University of Wales, Cardiff, also believe that the breakdown of traditional forms of male working-class employment could be driving young men to express their gender identity through steroid-assisted bodybuilding.

Some of them have psychological problems, manifested in excessive vanity and an inability to communicate with others, and some have histories of violence, researchers found. Although steroids may increase irritability and aggression in the gym, they believe it does not in itself make the users violent.

The study, which was commissioned by the Economic and Social Research Council, followed extensive fieldwork in gyms in south Wales. Professor Russell Dobash, who led the research team, said that the capacity of steroids to induce violence was similar to that of alcohol: "It is very important when considering the impact of steroids to investigate the personal and social characteristics of the individuals involved."

The ESRC report, based on the experiences of 67 gym users, 61 per cent of whom were steroid users, gives an extraordinary insight into the minds of bodybuilders yielded from a 27-page questionnaire and 3,000 pages of interview notes. One told the study: "If I eat the wrong foods, I can't cope with the guilt. It cracks me up." Another compared his obsession with attaining a perfect physique with those suffering from the eating disorders anorexia and bulimia. "You've got this phobia about being thin, so you want muscle," he said.

The bodybuilders were candid about their vanity and sense of power over others. One said: "It makes you a bit arrogant ... it makes you vain, very vain, you know." Another said: "Size is like a warning to people - `I'm strong and big don't mess with me'." The researchers noted: "It is probable that the narcissism associated with bodybuilding may accentuate orientations often associated with the commission of violence."

Steroid use is becoming increasingly accepted in the fitness industry, especially in the "hard-core" bodybuilding gyms where up to 90 per cent of attenders take the drugs. In Liverpool, the number of steroid users attending syringe-exchange clinics has increased from 26 (1.8 per cent of clients) in 1991 to 213 (19 per cent) last year.

Last month, the Government made the production, import or sale of anabolic steroids a criminal offence under the Misuse of Drugs act, following a succession of reports of steroid-induced violence and a series of scandals concerning their illicit use in sport as performance-enhancing drugs.

However, police drugs squads appear uncomfortable with the new legislation. Pat Lenehan, of the Drugs in Sport Information Service, said that despite the new legislation, steroid dealers were not widely seen as criminals. "The police view seems to be that they regard their role as an educational one," he said. "They don't want to get drawn into another drug when they have got enough on their hands with heroin and cocaine."

The ESRC findings indicate that the legislation may not have been necessary. As well as concluding that anabolic steroid use does not directly cause violence, the team found that the culture of bodybuilding did not condone or promote violence.

Previous studies had identified a phenomenon dubbed "roid rage", by which steroids inevitably drove users to acts of violence. One study referred to users developing "manic and psychotic symptoms, culminating in violent crimes". In the United States and Australia, defence lawyers have cited steroid use in mitigation pleas when defending clients accused of criminal violence.

But the ESRC study drew very different conclusions from evidence gained through unprecedented access to the underground world of steroid use by employing an accomplished bodybuilder to carry out much of the fieldwork.

Lee Monaghan spent two years using gyms across south Wales and working as a doorman at local nightclubs wherebodybuilders are employed. Only one of the 67 respondents that he tracked down for the study blamed steroids for his violent behaviour.

However, although the users denied a connection between their drug use and violence, one female gym user, who had lived with a steroid-using partner, disagreed. "If we've been out and somebody's looked [at me], normally he wouldn't say anything, but if he's been to the gym and he's back on steroids ... he'd be over there straightaway and smack, that would be it," she said.

A separate study by the Drugs in Sport Information Service found that 20 per cent of steroids users said they had urges to harm others. While finding no evidence directly linking steroids and violence, the ESRC team agreed with previous reports that steroid use can lead to diseases of the liver and coronary arteries. It can also cause chronic acne and diminished sex drive.

Most steroid users, however, do not feel that they have a problem. They blame the doctors and politicians for banning the sale of the substances they know as "the gear".

One told the researchers: "They [doctors] don't like the idea of muscular people going around. They are mostly a bunch of fat slobs.

"I think they're probably a bit insecure due to the state of their own bodies, secretly a bit jealous."