Angels, Devils and a Devastating Disease

(December 27, 2007) -- So, what's the damage, then? How much did you spend in the sales? If you woke up this morning with a living room full of gadgets, or a shoe collection to rival Imelda Marcos, you're probably still feeling giddy with the head-buzz of the annual joyride down Princes Street or through Buchanan Galleries.

For most of us, the fear will probably kick in shortly after Hogmanay, or as soon as the credit-card statement arrives. But for some, the spending cravings will be too much to resist. So why do some people get hooked on instant rewards?

To find out, scientists are using brain scans to home in on the engines in our minds that fire up when we make impulsive decisions. They are learning that the brains of, say, chocoholics or pathological gamblers are biologically different from those of the majority of us.

In a study published yesterday in the Journal of Neuroscience, US scientists found that addicts of one type - alcoholics - were more likely to crave and engage in other types of impulsive behaviour. So when someone says they have an "addictive personality", they might really mean it.

What's more, they might have been born that way. The researchers found a gene that appeared to prime people to behave impulsively - one linked to dopamine, the brain's pleasure messenger. This provides some of the best evidence yet that addiction is not so much a behaviour as an inheritable disease.

"It wasn't that long ago that we believed schizophrenia was caused by bad mothers and depression wasn't a disease," says Professor Charlotte Boettiger, who led the study at the University of California. "Hopefully, in 10 years we'll look back and it will seem silly that we didn't think addiction was a disease, too."

Using sophisticated brain scanning, Boettiger and her colleagues were able to map the brain circuits that drive addictive behaviour. They recruited 19 participants: nine recovering alcoholics, and 10 with no history of substance abuse. All were faced with the same hypothetical scenario: take money now, or wait and be given more later. The recovering alcoholics chose the "now" reward almost three times more often than the other group, reflecting a tendency toward more impulsive behaviour.

What the researchers wanted to know was: why? So they measured activity in several key brain departments. You could say these act like the devils and angels on our shoulders - the louder they shout, the more they influence the tug of war to control our willpower. Take, for example, the orbital frontal cortex - one of the angels, if you will. The study revealed it was less active in the brains of people who preferred "now" over "later". This fits with what we already know about patients who suffer damage to their orbital frontal cortex: they generally suffer impaired judgment and act impulsively. "Think of the orbital frontal cortex as the brakes," Boettiger explains. "With the brakes on, people choose for the future. Without the brakes, they choose for the short-term gain."

So where is the accelerator? The team found two sites - the "devils" - that co-operate to push us to indulge our cravings: the dorsal prefrontal cortex and the parietal cortex. High activity in these two areas tallied with a bias towards immediate rewards.

"Our data suggests there may be a cognitive difference in people with addictions," says Boettiger. "Their brains may not fully process the long-term consequences of their choices. They may compute information less efficiently."

What is exciting about this study, she adds, is that it suggests "a completely new approach to therapy" for addictive behaviours. "We might prescribe medications, such as those used to treat early Alzheimer's disease, or tailor cognitive therapy to improve brain function."

It may seem perverse to suggest drugs as the answer to addiction. Yet while they will not be a magic bullet, they could well provide a helpful kick-start for a patient who is undergoing other forms of therapy.

So what does all this tell us about the root nature of addiction? After all, not all brain changes are indicative of disease. Learning itself changes the brain - scans of London cab drivers and virtuoso musicians show unusual patterns that have been honed and reinforced by practice. But nobody argues that this means they are ill.

Clearly, brain scans alone cannot prove that addiction is a disease. But, crucially, Boettiger's team went a step further. They uncovered evidence that compulsive behaviour has its roots in our DNA. While there might be no such thing as a single gene that makes someone a compulsive gambler or an alcoholic, there will certainly be genes that tip the balance.

In their study, the researchers focused on a gene called COMT. A variant of this gene is associated with lower dopamine levels than normal, and the study showed that people with two variant copies of COMT - resulting in the lowest dopamine levels - chose "now" over "later" significantly more often. Some of us, it would seem, are born pleasure-seekers. The dice are loaded against us.

"It's not unlike chronic diseases such as diabetes," says Boettiger. "There are underlying genetic and other biological factors, but the disease is triggered by the choices people make.

"We have a lot still to learn. But the data takes a significant step toward being able to identify subtypes of alcoholics, which could help tailor treatments, and may provide earlier intervention for people who are at risk of developing addictions."

Source: The Herald

Last updated: 12/07

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