Paedophiles and rapists who undergo professional psychological treatment while behind bars are 30 per cent less likely to reoffend when released, according to a groundbreaking new study.

In what has been hailed as a world first, research by a University of Canterbury Masters student has shown a clear, direct link that specific treatment results in a drop in recidivism by sexual offenders.

UC psychology Professor Randolph Grace, who oversaw the research by psychology Masters student Lucy Moore, says that while the findings may seem a "no-brainer", documenting a link between prison-based treatment programmes and reductions in reoffending was "very challenging".

"There's a lot of debate about the efficacy of psychological treatment for sexual offenders and a lot of technical issues why it's a difficult question to resolve," Professor Grace said today (Wednesday).


Ms Moore examined the criminal history and post-release outcomes for 428 sexual offenders who were treated at Rolleston Prison's Kia Marama unit.

They were compared with a cohort of 1956 offenders who were also incarcerated for sexual offending but did not receive comparable treatment.

Professor Grace said results showed that the Kia Marama psychological treatment programme was associated with a 29 per cent reduction in sexual reoffending (from 10 per cent to 7.2 per cent) and the reduction was statistically significant.

"There were also significant reductions in violent and general reoffending for the Kia Marama group," he said.

More than 800 offenders have completed the Kia Marama programme since it opened in 1989.

The study, published in the Journal of Consulting and Clinical Psychology, was important because it was the first to demonstrate that specific treatment gains were linked to reductions in recidivism by sexual offenders, Professor Grace said.

Wellington Rape Crisis agency manager Natalie Gousmett said while it was a survivor or victim's right to see justice being served, the centre supported prison-based treatment programmes.

"We know they are effective and it's great to see there has been some robust research done to show it results in a reduction in reoffending," she said.

"We absolutely support the continuation and funding of programmes like that because our ultimate aim is to end all rape and sexual violence."

Dr Jarrod Gilbert, a criminologist and Howard League representative, also welcomed the findings.

Incarceration should always focus on reducing recidivism, resulting in less victims of crime, he said.

"We tend to see prison as a form of punishment, and so it should, serving an important component, but we miss a trick if we don't look to rehabilitate offenders while they are there."

Dr Gilbert would like to see more resources and rehabilitation available for all prisoners to try and bring down New Zealand's "stubbornly high recidivism rate".

"Our burgeoning prison population is testament to the fact that our current approach isn't working," he said.

"We have to get much more creative."