New research: Understanding testosterone's role in depression

Major depressive disorder affects women twice as much as men, but researchers are still trying to figure out why
.
Researchers at Michigan State University recently received a $3 million grant from the National Institutes of Health to continue studying how the male and female brains respond differently to stress and how testosterone is key
to enhancing resilience.

The National Institute of Mental Health has begun using sex as a variable to help explain some mental health differences
.
Since 2016, A.
J.
Robison, associate professor in the College of Natural Sciences and director of the Neuroscience Program at Michigan State University, and his team have been studying the effects of stress on the brain and found that sex and testosterone play a role
.

"Through earlier research, we found that female mice have a specific brain circuit in their hippocampus that is more likely to be excited
than male mice," Robinson said.
"This circuit is regulated by testosterone
.
"

Robison's team includes his wife, Michelle Mazei-Robison, who is co-principal investigator on the grant and associate chair of the Department of Physiology in the College of Natural Sciences, and graduate students Elizabeth "Liz" Williams, Claire Manning, Ivana Lakic and Chiho Sugimoto
.
Their research shows that testosterone reduces the excitability
of this brain circuit.

Mazei-Robison said: "I am excited to be part of this innovative project to analyze the mechanisms
that lead to gender differences in stress resilience.
" "These studies have the potential to identify targets that can be used to treat mood disorders
using new treatment strategies.
"

Since testosterone is at the heart of many of the body's functions, the answer is not as simple
as adding testosterone to people with depression.
By determining how testosterone affects neurons in neural circuits through signaling on the cell surface or binding of DNA within the nucleus, researchers can develop and utilize new targets to treat depression
in men and women.

"Now, we want to know how testosterone causes this change in brain circuitry
," Robinson said.
"If we can figure this out, maybe one of the things we can use to create a drug
treatment for depression that targets women or men.
"

This research has also led to new research
in related fields.
For example, Andrew Eagle, an assistant researcher in the Department of Physiology at Michigan State University and a former postdoc at Robinson University, is studying how the same brain circuits are linked to the reward effects and relapse behaviors associated with cocaine use, hoping to find new treatments for
substance use disorder.