Saturday, 25 December 2010

SOS: Save our Science - Last minute Christmas

Now that Christmas is drawing to a close our thoughts turn exuberantly towards the January sales. Blowing all of our new gift vouchers and our remaining money on last minute impulse buys. The good news for all of us is that we may be able to blame these rash choices on our genes.

Impulsivity is described as doing something without foresight, and understanding it has major implications for a range of psychiatric disorders as well as explaining what will be going on in the high street over the next few weeks. Impulsive behaviour is very complex and under the control of many genes. It has many aspects, most especially reduced inhibitions, but also including reduced attention span, limited awareness of consequences and inappropriate responses to rewards. Impulsive behaviour is also known to be inherited in some cases. This new study shows that it is possible to identify the genes involved in this behaviour.

Serotonin and dopamine signalling are essential to controlling behaviour. Genes involved in these systems were closely analysed in a group of Finnish people with strong and well characterised impulsive behaviour, allowing for easiest identification of differences. The Finns are often used as a human study group as they are almost all descended from a few very small groups of people, and have had little interaction with other races until relatively recently, as such they have distinct genetic markers. The medical history of Finnish families is also particularly well recorded, aiding studies over multiple generations.
One particular gene (HTR2B) was found to be non-functional in most of the most impulsive individuals. The dopamine system allows us to judge and understand punishments and rewards, whilst the serotinin system allows us to judge resource availability and social standing. Both dopamine and serotonin are neurotransmitters; they are chemicals which brain cells use to communicate with each other. 7.5% of impulsive individuals had the HTR2B marker, compared to less than 2% in the rest of the population. The exact effect of altering this gene in the brain is unknown. Functional HTR2B is linked to inhibitory signalling, preventing poorly considered decision making.

Comparison to over 3000 people worldwide, covering all backgrounds, shows that this particular gene change is specific to Finns, however defects in HTR2B are still likely to be involved in impulsive behaviour around the world. This is the limitation of so called founder populations; it is easy to identify genes affecting complex behaviour in a limited gene pool, but the findings may not always be applicable to the rest of the world. Confirming the role of HTR2B in other races is the most important follow up to this paper.

The strongest effects of HTR2B mutations are generally observed when inhibitions are further reduced by other factors. The most strongly affected are generally men; dopamine and serotonin signals are often related to testosterone levels, and altered HTR2B males often have higher testosterone and are more violent. This effect is also amplified by the effects of alcohol, when the strongest impulsive behaviour was observed.

The study suggests that roughly 106 000 Finns are genetically predisposed to impulsive behaviour by HTR2B. Males are most likely to act strongly on this predisposition, especially when stressed and under the influence of alcohol. This study has also aided dissection of Finnish history, identifying that all Finns are descendants of two waves of immigration 4000 years ago and 2000 years ago.

So, when you stagger home loaded down by all of your bargains from the January sales, remember; “It’s not my fault, it’s genetics.”

A Merry Christmas to all and to all a good night. Enjoy your shopping.

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