Men's brains have shrunk by 8pm every day.
A man's brain shrinks by the end of the day
Scientists scanned a 26-year-old male's brain 40 times over the course of 30 days and found it had shrunk by the evening before resetting overnight.
Experts at the University of California, Santa Barbara (UCSB) suggest that the cycle of shrinking and growing correlates with rising and falling levels of the steroid hormones testosterone, cortisol and estradiol.
Although alterations to the brain structure coincided with the daily cycle of steroid hormones, the researchers are unable to definitively conclude if the hormones are responsible for the changes.
Elle Murata, co-author of the study and a doctoral student in psychology and brain sciences at UCSB, said: "I'm convinced that hormones impact the brain and brain structure.
"But in this study, we can't say that it's directly causing it."
She added: "This is another example debunking the myth that hormones are only relevant for females."