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Ever wonder why some women seem to be more ill-tempered than others? The answer may partly lie in their genes, writes Roger Highfield.
Angelina Jolie as the aggressive treasure hunter in the movie Lara Croft: Tomb Raider
Genes as well as the environment â€” in the form of provocation, annoyances and miscellaneous bugbears â€” could have played a role in angry outbursts, say University of Pittsburgh researchers.
They report that anger, hostility and pugnacity may be genetic, rooted in variations in a serotonin receptor gene, that is the gene responsible in the protein that picks up the brain messenger chemical serotonin, one which plays a variety of roles, including in personality disorders. These findings â€œmay aid in establishing a potential marker for certain conditions associated with aggression and angerâ€, the team adds.
Dr Indrani Halder of the Cardiovascular Behavioural Medicine Programme at the University of Pittsburgh, presented the findings at the American Psychosomatic Societyâ€™s Annual Meeting, held in Budapest, Hungary.
Previous studies have associated the hormone serotonin with anger and aggression in both humans and animals and have shown that increased activity of serotonin is related to a decrease in anger and aggression. In the study presented by Dr Halder, researchers sought to determine if this relationship was genetically determined.
The study, the first to look at the relationship between variations in the serotonin receptor 2C gene and anger and hostility, focused 550 unrelated women of European descent. In order to find normal variations in genes and behaviour, the women were not prescreened for behavioural type.
Researchers found that those who had one or both of two alterations in the promoter region of the serotonin receptor 2C gene â€” the part of the gene that turns it on â€” were more likely to score lower on two common tests for anger, hostility and aggression.
Testing for these markers could have wider implications. â€œAggression and hostility are predictors of hypertension, glucose metabolism and heart diseases,â€ said Dr. Halder. â€œThe genetic marker we found for hostility also may be useful for predicting a person’s predisposition to such diseases,â€ adding that this will be the subject of follow up studies.
But the work was greeted with some scepticism. â€œItâ€™s wildly premature to envisage the serotonin receptor 2C gene, or any gene, being used as a test for a tendency to angry aggression,â€ commented Prof Terrie Moffitt of the Institute of Psychiatry, London. â€œHowever, this study fits another key piece into a thousand-piece jigsaw puzzle: why are extremely emotional people more likely to develop heart disease?â€
Individual differences in aggression and anger are influenced by genes â€” as are all personality traits â€” but progress in identifying the genes has been slower than researchers expected,â€ added Prof Robert Plomin, deputy director of the Social, Genetic and Development Psychiatry Centre, London. â€œThousands of reports of this gene or that gene being related to complex traits or common disorders in the end fail to replicate, not just for behaviour but also for medical problems such as dementia and heart disease.â€ Rather than looking at one gene at a time, most researchers have moved on to more systematic approaches that scan the entire human genetic makeup â€” genome â€” with hundreds of thousands of DNA markers, he said.
â€œIn addition, most researchers now assume that we are looking for many genes of small effect which implies that very large samples with many thousands of subjects are needed in order to detect these associations of small effect size.â€
Prof Plomin is also sceptical. â€œBecause the Halder paper looks at only one gene in a relatively small sample, I bet that this report will join the ranks of thousands of other reports that fail to replicate.
On the other hand, in dozens of studies of humans and rodents, serotonin has been shown to play a role in emotional responding so it is not unreasonable to consider DNA variations in the serotonin transporter as a source of individual differences in aggression and anger. I would just need a lot more convincing.â€
Dr Halder told The Daily Telegraph: â€œI agree that our study needs replication in larger samples, but a genomic scan does not negate the necessity of testing known candidate genes, one at a time if necessary, to understand exactly how the gene causes/influences a trait. We were not scanning the genome, rather attempting to investigate how variations in one particular gene influence a personality phenotype, based on certain hypotheses regarding the function of the gene.â€
Source:The Telegraph (Kolkata,India)