Science

A Junkie’s Logic

Every day a different celebrity name is splashed across the newspapers for entering rehab. It’s not just the rich and famous, however. People from all walks of life can become addicts. Addictions can range from alcohol, smoking and drugs, to gambling, sex, shopping, and the internet. Illegal substances aside, most of these pastimes are socially acceptable in moderation. But in excess such compulsive habits can be damaging to a persons health, finances and relationships. So why do some people become uncontrollably hooked?

It seems the answer may lie in abnormalities in the decision making parts of the brain. A three year study into addiction has recently begun at The University of Nottingham. The work, funded by the Medical Research Council, involves using scanning equipment to compare differences in the brain function of daily smokers and social smokers. Dr Lee Hogarth from the Department of Psychology took the time to explain to Impact Science what his work entails.

Decision making is all to do with weighing up costs and benefits. Addicts expect to gain an unusually high benefit from the behaviour or substance they are addicted to. Dr Hogarth explains that this expected benefit is “much higher than the most pleasurable thing you can think of.” So it is not really surprising that an addict will return for more. To the addicted even though the negative consequences or costs associated with the behaviour might be high, they do not outweigh the perceived benefit.

There are two ways in which the brain calculates these costs and benefits. Firstly there is the dopamine system that is activated when a person or animal experiences something that is favourable to survival or reproduction, such as food or sex. Dopamine is a chemical signal that acts in the middle part of the brain to create a feeling of pleasure or reward which encourages the beneficial behaviour to be repeated. The release of dopamine can be initiated by other behaviours such as drug use. To control the action of dopamine the brain contains receptors that inhibit its effects. Addicts often have an unusually low number of these inhibitory receptors. This means that the brain is overly stimulated by dopamine and so the feeling of reward is more intense.

The second system is the frontal cortex. This is the part of the brain that controls planning and reasoning – it weighs up the long term values of an action. Addicts often have underdeveloped frontal cortex areas, sometimes due to psychiatric illness. Young people up to the age of 25 are also at high risk of addiction because their frontal cortex is not yet fully developed but the dopamine system of the mid brain is mature. There is a mismatch between the systems meaning that short term reward is appreciated but is not effectively balanced by long term reasoning.

The study aims to investigate how action in the prefrontal cortex part of the brain differs between nicotine addicts and non-addicted smokers. The processes occurring in the brain will however be similar for decision making in people with other types of addiction. Hogarth explained that the work is hoped to encourage investment from the pharmaceutical industry. Possible drugs may be investigated that could improve abnormality in frontal function. This would enable people to more effectively weigh up the consequences of their addictions and so make the decision to break the habit.

Treatments for addiction have so far been somewhat overlooked. This is partly because the proportion of addicts in the population is much lower than those suffering other illnesses such as asthma or cancer. Also society tends to look upon addicts as having decided to take drugs or begin gambling etc, so they are often blamed for getting themselves into difficulty. Whilst obviously there is choice involved, this study may go some way to showing that this choice is not completely free. The decision making system in many addicts is essentially broken. Dr Hogarth told Impact that the study has the potential to show that, “an addict’s freewill is undermined.”

With no addiction treatments currently in the pharmaceutical pipeline the work being carried out here at Nottingham is a significant first step. The findings could have important consequences for tackling the growing problem of addiction in our society, but the effect of the results will be a long time coming.

By Laura McGuinness

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