But a University of Wollongong researcher says they possibly should be, after her study found significant differences between the brain samples of males and females with depression.

In findings she hopes lead to more targeted drugs for men and women, Dr Samara Brown found females with depression had molecular changes in their brain that did not occur in males.

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As well as implications for treatment, Dr Brown said her findings showed how important it was for medical researchers to consider differences between men and women.

"We can no longer just look at depression with males and females together because, even at a fundamental level, the brains are so different biologically that when we group them all together for these studies, we miss so much," she said.

The recently published research looked at molecular changes in a pea-sized piece of tissue from 80 postmortem samples from a "brain bank" for medical research.

Focusing on the emotional processing centre of the brain, it compared the molecular characteristics of males who did and didn't have depression, as well as the brains of women who did and didn't have depression.

In women with depression, there was less of a certain substance - kynurenic acid - which can protect the brain by blocking toxic damage, Dr Brown said.

"This means there is more potential for damage in the brain," she said.

She said researchers have, in the past, tried to target the chemical pathway which leads to the production of kynurenic acid, but have not accounted for the differences in male and female brains.

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"One of our big conclusions is that males might not need treatment that targets this pathway, and females would potentially benefit from something targeting and trying to increase that neuroprotection," she said.

"At the moment, there's no rules for treating men and women differently, and I would say it honestly depends on the doctor or psychiatrist and whether they take things like that into consideration.

"But we need to be considering how males and females differ in the underlying changes in the brain so that we can better treat both sexes."

The researchers also looked at a subgroup of people who died by suicide, who also had less of the protective kynurenic acid.

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"So in addition to treatments aimed at targeting depression in females, we thought the same drugs could be used for individuals who are at risk of suicide, irrespective of sex," Dr Brown said.

"What we're showing is that females and individuals at risk of suicidality may benefit from a specific type of medication that works with the kynurenine pathway.

"The research is a step towards acknowledging that there are differences between [depression] patients, and a one-size-fits-all approach won't work.

"If we can understand at least some of what is going on in the brain, we can work out who might be more suited to diverse types of treatment."

Dr Brown said her research was part of a wider push to make sure the differences between men and women's bodies are considered in medical research.

"In a lot of the rodent studies, which is usually where new drugs are developed, until recently they were all trailed in male rodents," she said.

"So all these drugs were initially designed based on a male model."

She said this was because researchers felt the rats' estrous cycle - which is similar to women's mentrual cycle - made things "too complicated".

"Funnily enough women have a estrogen cycle similar to the estrous cycle, and we are 50 per cent of the population so it's kind of important to include that," she said.

"It is great to see that is changing and that a lot more researchers are including both males and females in these pre-clinical models."