Medically reviewed by Susan Kerrigan, MD and Marianne Madsen
Additions/comments by Urologist Steven N. Gange, MD
John Gray, the popular American author and relationship coach, first coined the phrase “men are from Mars and women are from Venus.” This has become a way to describe the very different ways in which the different sexes function–and it seems that many of these differences originate in puberty. Adolescence is a time of increased divergence between males and females in physical characteristics, behavior, and risk for psychopathology. While gender equality and other sociological and political issues underlying the varying roles of men and women are hot topics at the moment, exploring these is not the purpose of this article. This article is of a purely biological nature and seeks to understand how the brain and brain networks develop differently in males and females during puberty and to understand what that actually means–and some of the possible medical implications of these differences.
The most consistent sex difference between the brains of men and women is the 9-12% larger brain size that has been reported in males. Individual brain regions that have most consistently been reported as different in males and females include the basal ganglia, hippocampus, and amygdala. A woman’s hippocampus, critical to learning and memorization, is larger than a man’s and works differently. Conversely, a man’s amygdala, associated with the experiencing of emotions and the recollection of such experiences, is bigger than a woman’s. It, too, works differently.
Connection between brain differences and psychiatric disorders
Recognition of the importance of the adolescent period in the origin of common psychiatric disorders such as schizophrenia and depression has gained attention and has sparked interest in how brain development differs between males and females. Does this difference contribute to their relative risks for specific disorders? Before the onset of puberty, males and females have approximately equal rates of depression at 5%. However, with the onset of puberty, rates in females double, while males stay approximately the same.
Studies supporting differences in brain connection development during puberty
According to a recent groundbreaking study, mood upsets, particularly anxiety and depression, occur disproportionately in girls, and women are twice as likely as men to suffer from depression following the trend emerging during puberty. The study found that the puberty period is associated with significant brain changes in these mood-related brain areas; however, this correlation requires further verification.
In the study, researchers took images of the brain activity while the adolescent volunteers were lying still in an MRI scanner. These images were corrected for age and then were analyzed in a way that measures how strongly brain regions communicate with one another (known as “functional connectivity”). Studies indicate that the increase in incidence of depression is linked to pubertal maturation rather than increases in chronological age.The values of the functional connectivity of these regions were then analyzed to see if there was a connection with the level of maturity at puberty. These findings are groundbreaking as, for the first time, researchers were able to measure brain changes directly against childrens’ puberty status. Furthermore, the differences in scores between boys and girls (measured according to their stage of puberty) that resulted from the study were statistically significant.
Dr. Harro commented on this important work saying that “This imaging study offers a potential brain correlate to these distinct interactions, and it is quite plausible that they might arise during adolescence.”
The importance of identifying and understanding sex differences in brain development is the possibility that treatments may not have the same effects in males and females. This may be important to explore further for the goal of optimizing individual treatment strategies and maximizing the efficacy of treatment. However, while these studies definitely point to both structural and functional differences between the brains of men and women that appear to originate during adolescence, further supporting research is required in order to more definitively draw any causal conclusions.