Three-quarters of all people detained by Kings Cross police had drugs in their system, raising concerns over the link between performance-enhancing drugs and Sydney's culture of violent assaults.

Experts fear rising steroid use is contributing to aggression and violent crime among young men.

Steroid use has been rapidly increasing in Australia with arrests hitting an all-time high in 2011-12, according to the latest Australian Crime Commission data.

Detections by Customs increased by more than 500 per cent in six years and hit a decade-high of 8726 in 2011-12.

Steroids have become a common feature of major drug raids, bikie arrests and gun crime investigations in Sydney, police say.

Two violent brawls between bikies last year led police to huge steroid caches. Vials of assorted steroids were found in the homes of four Rebels bikie gang members who allegedly punched, kicked and smashed chairs over a man inside a Mount Pritchard gym in February.

Three months later, police again seized large amounts of steroids, cocaine and ammunition after several Comanchero and Hells Angels gang members brawled inside a Paramatta pub at lunchtime. No one has been arrested.

Police also found steroids at the homes of many of the 33 members of a western Sydney crime gang smashed in September and the 13 people arrested in the latest anti-gun crime blitz, Operation Apollo.

Peter Miller, author of the largest-ever study into alcohol-related nightlife crime in Australia, found overwhelming anecdotal evidence that steroid use was fuelling assaults in nightspots.

He has applied for a grant with Deakin University colleague Dr Matt Dunn to conduct the first-ever research into the link between steroids and violent crime in Australia.

''The bouncer informants definitely talked about more young people on steroids and how they were more aggressive,'' he said.

More than 70 per cent of police detainees at Kings Cross tested positive to at least one drug type, according to testing by the Australian Institute of Criminology's Drug Use Monitoring in Australia in 2009-2010.

The most commonly detected drugs were opiates followed by benzodiazepines, cannabis, heroin and amphetamines.

The most recent DUMA testing in 2012 found a similar story across the country - two thirds of offenders having drugs in their system.

Associate Professor Miller said steroids and methamphetamine were contributing factors in anti-social behaviour ''but they're still not the elephant in the room, which is alcohol''.

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