Researchers at a leading medical institution reported that female lab rats showed steadier behavior than males across hormonal cycles, underscoring the importance of including both sexes in scientific studies. The work was published in Current Biology and highlights a key issue in biomedical research design.
Neuroscientists conducted an open field study with mice and observed that the female hormone cycle had little impact on behavior. In addition, the study noted that behavioral differences among men were more pronounced than those among women, suggesting wide variation within sexes that researchers should account for when interpreting results.
Both mouse and human brains share a similar structural organization, which is why mice serve as common model organisms for exploring a range of diseases. For decades, however, studies have relied predominantly on male mice. An analysis from 2011 showed men were used roughly five times more often than women in many experiments.
This historical bias has led to gaps in understanding how the female brain responds to illness and treatment, contributing to misdiagnosis of mental and neurological conditions in women and to the development of drugs that produce more side effects for women. The issue is thought to stem in part from the belief that fluctuations in female hormone levels complicate studies and muddy results.
The new study challenges this assumption, presenting evidence that the traditional view lacks solid scientific justification. It stresses the need to broaden the pool of laboratory subjects to include more female mice in neuroscience and related fields.
Researchers cautioned that the conclusions come from a specific set of laboratory mice, so the findings should not be generalized to all species without further testing. Nevertheless, the results offer strong support for expanding the use of female subjects in neuroscience research and beyond.
Lead author Dana Levy commented that the example illustrates how often the methods shaping scientific inquiry rest on untested assumptions. It is important to evaluate these beliefs directly because they may not hold true in practice. This perspective reinforces the push toward more inclusive study designs that better reflect real-world biology and human health in Canada and the United States.