Drug users who can't kick the habit can blame a dysfunctional brain for their addiction, according to new research.
A study by the University of Melbourne has found long-term drug users have difficulty controlling impulses because their frontal cortex is impaired.
The two-year study found opiate users neededto use more of their brain to resist impulses in a test of self control than those who were clean.
The findings shed new light on why drug addicts find it so hard to quit, despite the health consequences.
"Drugs can capture and hijack some parts of the brain," said Dr Murat Yucel, a lead researcher in the study.
"In this study we found the frontal cortex, an area that is essential for exercising control over thoughts and behaviours, was working inefficiently.
"These findings may help explain why it takes addicted individuals enormous effort to exercise control over their drug taking behaviour in the face of adverse consequences and why they are vulnerable to relapse into uncontrolled, compulsive patterns of use."
The study, published in the journal Molecular Psychiatry last month, also found drug users' brain cells in the frontal region were less healthy than normal.
The research shows drug taking is not a matter of choice for long-term users, who have a reduced biological capacity to stop, Dr Yucel says.
Researchers will next examine whether reduced brain function is a consequence of addiction or a contributing factor that makes some people more vulnerable to drug abuse.
Co-researcher Dan Lubman said the study would likely lead to the development of new strategies for the treatment of addiction. "These findings tell us that we need to provide a combination of pharmaceutical and psychological treatments that will help bolster the efficiency of the frontal cortex and hence the individual's ability to stop their urge to use drugs.
