Sex Differences Extend Into The Brain

Discoveries by scientists over the past 10 years have elucidated biological sex differences in brain structure, chemistry and function. “These variations occur throughout the brain, in regions involved in language, memory, emotion, vision, hearing and navigation,” explains Larry Cahill, Ph.D., an associate professor in the Department of Neurobiology and Behavior at the University of California, Irvine.

While women and men struggle to communicate with each other and ponder why they don’t think and react to things in similar ways, science is proving that the differences in our brains may have more serious implications beyond our everyday social interactions.

Scientists are looking into ways that sex-based brain variations affect the thought processes and behavior of men and women differently. According to Cahill, “their discoveries could point the way to sex-specific therapies for men and women with neurological conditions such as Alzheimer’s disease, schizophrenia, depression, addiction and post-traumatic stress disorder.”

To better understand the implications of sex differences in the brain, it is important to examine disease entities in depth. Take Alzheimer’s disease, for example. Significant differences exist between men and women who suffer from the disease.

“There are growing indications that the disease pathology, and the relationship between pathology and behavioral disturbance, differs significantly between the sexes,” Cahill wrote in a paper published in Nature Reviews Neuroscience. Pathology refers to the way a disease develops within the body.

“Let us first consider Alzheimer’s disease-related pathology. Alzheimer’s disease-related neurofibrillary pathology associated with abnormally phosphorylated tau protein differs in the hypothalamus of men and women: up to 90 percent of older men show this pathology, whereas it is found in only 8-10 percent of age-matched women.”

In other words, abnormalities caused by Alzheimer’s disease may differ between the sexes and result in different symptoms or behavioral problems for women and men with the disease.

There are several other notable differences in pathology between the sexes in Alzheimer’s disease. Gaining a better understanding of the relationship between pathology and how disease presentation affects men and women differently could pave the path for future sex-specific therapies.

Schizophrenia is another disease that affects men and women differently. Differences include age of onset, symptoms and the time course of the disease. In addition, structural brain differences are apparent. According to Cahill, “men with schizophrenia show significantly larger ventricles than do healthy men, whereas no such enlargement is seen in women with schizophrenia.”

Researchers do not understand the implications of these differences yet, but the study of sex differences in the brain is advancing quickly. Aiding researchers in their work is a new guidebook for investigating sex differences in the brain. Published by Oxford University Press, “Sex Differences in the Brain: From Genes to Behavior” provides scientists with the basic tools for investigating sex differences in brain and behavior and insight into areas where important progress in understanding physiologically relevant sex differences has already been made.

The book is edited by members of the Society for Women’s Health Research’s Isis Fund Network on Sex, Gender, Drugs and the Brain.

“Scientific evidence of sex differences in the brain is regularly emerging now,” said Sherry Marts, Ph.D., author of the book’s preface and vice president of scientific affairs for the Society for Women’s Health Research. “This book outlines current knowledge, conceptual approaches, methodological capabilities, and challenges to continued progress. It is an important tool in the quest to turn the science of sex differences into appropriate care for all patients both male and female.”

As researchers continue to explain how sex influences brain function, we will see more diagnostic tools and therapies that successfully account for the biological differences between women and men. That will mean better health outcomes for all patients.