Scientists have found "significant abnormalities" in the brains of people addicted to cocaine, which could help explain some of the compulsive behaviour associated with using the drug. It may also hint at why some people are more prone to addiction.

Brain scans revealed that cocaine users had a "dramatic decrease in grey matter" in their frontal lobes, according to researchers, which affected key functions including decision-making, memory and attention, while some of their brain's rewards systems were significantly bigger. Karen Ersche of the Behavioural and Clinical Neuroscience Institute at the University of Cambridge, who led the latest work, found the longer a person had been using cocaine, the poorer their attention was, and the more compulsively they used the drug.

"That is the hallmark of cocaine dependence - namely, that most of them are intelligent people who go to great extents to buy cocaine, to get more cocaine, to put their jobs at risk, their families at risk,They feel like they're driven to use more" said Ersche.

The results were published on Tuesday in the journal Brain. Ersche and her team scanned the brains of 60 people who were dependent on cocaine and compared them to scans of 60 people without any history of drug-taking. "We found significant abnormalities in the brains of the cocaine users," she said.

Specifically, the amount of grey matter in the orbitofrontal cortex was reduced in people with cocaine addiction, an area involved in decision-making and goal-directed behaviour.

Other affected areas included the insula, an area of the brain involved in feedback processing, learning and feelings of cravings. The grey matter in the anterior cingulate, involved in emotional processing and being attentive, was also reduced.

In contrast, a region deep in the brain associated with reward processing, attention and motor movements - the caudate nucleus - was enlarged in subjects who were addicted to the drug. This could explain why those subjects were more prone to addiction but the scientists cannot be sure whether the enlargement is a result of cocaine use.

Laurence John Reed, a clinical senior lecturer in addiction neurobiology at Imperial College London, said the "most impressive" results were the basic comparison of controls and stimulant users, which showed how parts of the brain remodel themselves in response to drugs. "This is a striking and visual example of how addictive stimulant use can result in adaptation of very important brain systems which have a direct correlates with behaviour – specifically inattention, impulsivity and compulsivity – and really does underline why we need a much better neurobiological understanding of the processes involved."

Ersche said that, though she found links between brain structure and cocaine use,her research was not conclusive on which came first. "At the moment, correlation shows me a direct relationship - but I don't know which direction the relationship is. Has this been caused by cocaine, or are people who have this abnormality more vulnerable?"

But the work could be used to help in diagnosis and treatment of addiction.

"We basically show that cocaine is a disorder of the brain, which is a big step," said Ersche. "For a lot of people, it is still a moral issue and willpower has nothing to do with the brain."

Knowing that certain brain areas are abnormal, she said, meant that scientists could try to work out ways of training or medicating the brain to get around the damage.

In a separate study published in the journal Heart, scientists at the Foundation CNR-Tuscan Region in Pisa, Italy, found that heavy cocaine use also causes serious damage to the heart, without any obvious symptoms at the early stages. Scans of the hearts of 25 men with long-term history of cocaine use picked up structural damage in 83% of participants and swelling in the lower left ventricle in around 47%. They also found tissue scarring in 73% of addicts, possibly a result of undetected heart attacks.

Around one in five cocaine addicts suffer from an inflammation of heart muscle, known as myocarditis, and the researchers said that a quarter of non-fatal heart attacks among the under-45s are associated with cocaine.

• This article was amended on 23 June 2011. The original said a region deep in the brain associated with reward processing, attention and motor movements was called the chordate nucleus. This has been corrected.