Why only some people become addicted to drugs: Scans of cocaine users reveal brain shape could be to blame

Drug users who aren't dependent have an abnormally large frontal lobeThis section of the brain is implicated in self-controlThose who didn't become addicted had a low-boredom threshold

By
Claire Bates

PUBLISHED:

17:06 GMT, 18 January 2013

|

UPDATED:

17:09 GMT, 18 January 2013

People who take cocaine over many years without becoming addicted have their brains to thank, a study has found.

Researchers found recreational drug users who do not
develop a dependence have an abnormally large frontal lobe, the
section of the brain implicated in self-control.

The Cambridge University study asked individuals who used cocaine on a regular basis to undergo a brain scan
and complete a series of personality tests. While the majority of the cocaine
users were addicted to the drug there were some who were not despite having used
it for several years.

Pink blobs (left) show where cocaine-dependent people have less grey matter than normal. Red blobs (right) show the frontal lobe where recreational cocaine users have more grey matter than normal

Pink blobs (left) show where cocaine-dependent people have less grey matter than normal. Red blobs (right) show the frontal lobe where recreational cocaine users have more grey matter than normal

The scientists discovered that a region
in the frontal lobes of the brain, known to be critically implicated in
decision-making and self-control, was abnormally bigger in these
recreational cocaine users.

They suggested that this
abnormal increase in grey matter volume, which they believe predates
drug use, might reflect resilience to the effects of cocaine.

The team found that the same region was significantly reduced in size in people
with cocaine dependence. However, they believe at least some of these changes were the result of drug use, which eroded what self-control they had.

Dr Karen Ersche suggests personality type and brain structure both played crucial roles in addiction

Dr Karen Ersche suggests personality type and brain structure both played crucial roles in addiction

Study leader Dr Karen Ersche, told Mail Online: 'Drug addiction never happens overnight. It needs continued use to take hold as a habit.'

The personality tests revealed that people who developed a dependence had two traits that could be harmful when combined – that of being impulsive and compulsive. This gave them an often uncontrollable urge to act without thinking as well as a need to repeat behaviours that then became habits.

In contrast those who didn't become addicted were sensation-seekers like addicts, however they also became bored quickly and moved on to other behaviours and experiences.

Dr Ersche, said: 'These findings are important because they show that the use of
cocaine does not inevitably lead to addiction in people with good
self-control and no familial risk.

'Our findings indicate that preventative
strategies might be more effective if they were tailored more closely
to those individuals at risk according to their personality profile and
brain structure.'

The researchers will next explore the basis of the recreational users’ apparent resilience to drug dependence.

Dr Ersche added: 'Their high level of
education, less troubled family background or the beginning of
drug-taking only after puberty may all play a role.'

Their research was
published in the journal Biological Psychiatry.