Why stress makes men more aggressive than women
By William Smith
When we feel stressed, both men and women have the same symptoms. Typically we have experience our 
heart pounding and adrenaline pumps through along with other debilitating symptoms. A new study suggests that although both men and women may have similar symptoms, a single gene in men is responsible for aggression under stress.
The study can be found in BioEssays and was conducted by researchers from Australia’s Prince Henry’s Institute in Melbourne.
Previous studies have been conducted which explain how the body responds to stress, activating the adrenal glands. This in turn causes catecholamine hormones to be secreted into the bloodstream and is responsible for triggering the flight-or-fight response. Most of these studies have centred on men and have not identified whether there could be differing responses in men and women.
Dr. Joohyung Lee from the Prince Henry’s Institute says ‘Historically males and females have been under different selection pressures which are reflected by biochemical and behavioural differences between the sexes. The aggressive fight-or-flight reaction is more dominant in men, while women predominantly adopt a less aggressive tend-and-befriend response.’
The two authors, Dr. Lee and Professor Vincent Harley suggest that the Y-chromosome gene SRY shows us the genetic foundation for this difference. SRY is responsible for controlling a group of neurotransmitters known as catecholamines. In a previous study Dr. Harley found that SRY is a sex hormone which has the effect of masculinising the body as it develops.
Professor Harley said ‘If the SRY gene is absent the testes do not form and the foetus develops as a female. People long thought that SRY’s only function was to form the testes. Then we found SRY protein in the human brain and with UCLA researchers led by Professor Eric Vilain showed that the protein controls movement in males via dopamine.’
Dr. Lee added ‘Besides the testes, SRY protein is present in a number of vital organs in the male body, including the heart, lungs and brain, indicating it has a role beyond early sex determination. This suggests SRY exerts male-specific effects in tissues outside the testis, such as regulating cardiovascular function and neural activity, both of which play a vital role in our response to stress.’
SRY may make the organs in a male body ready to respond to stress by releasing a higher level of catecholamine and blood flow to organs, the authors suggest. It may also be responsible for aggression and increased movement which is associated with flight-or-fight in men. It is oestrogen that activates internal opiates in women. The opiates are used by the body to control pain and may prevent aggressive reactions in women.
Dr. Lee concludes ‘New evidence indicates that the SRY gene exerts ‘maleness’ by acting directly on the brain and peripheral tissues to regulate movement and blood pressure in males. This research helps uncover the genetic basis to explain what predisposes men and women to certain behavioural phenotypes and neuropsychiatric disorders.’
The authors suggest that the part which SRY plays in the regulation of catecholamines may suggest that it may have a hand in disorders which are male-biased, disorders such as Parkinson’s disease.
