New Study: Working This Many Hours Per Week Could Change Your Brain

With rising costs of living (beef, for example, saw a record high this month), maybe it shouldn’t be surprising that one in four Americans has a side hustle—that’s according to a 2025 report from finance news site Bankrate. Whether you grind through one job or more, new research challenges you to keep in mind: if you regularly work more than the standard 40 hours a week, your brain could be changing.

Publishing details of their study in May 2025 in the peer-reviewed British Medical Journal‘s Occupational & Environmental Medicine, a team of medical doctors and biomedical engineers in Korea set out to investigate whether overworking could potentially influence a person’s functions for thinking and regulating emotion.

To do so, they classified 110 participants—specifically, healthcare workers—into two groups: those who were overworked (working 52 hours or more each week) and those “working standard hours.” Participants’ brains were scanned, and those MRI images were examined.

The researchers determined that the participants who were overworked experienced structural brain changes in areas associated with cognition and emotion. Specifically, there appeared to be a “significantly larger volume” among those in the overworked group in a section of the frontal lobe—in a brain region responsible for processing reading and the ability to work with numbers.

Additionally, there were “peak increases” in 17 regions of the brain, including areas related to anxiety, speech, language, and short-term memory.

But doesn’t a larger area of the brain mean this area is higher-functioning? Neuroscience experts say it can depend on the area of the brain and the circumstances. (Shrinking, or “atrophied,” areas of the brain can indicate lower cognition among some older individuals.) What the researchers in Korea wanted to find was whether a long work day led to altered “brain morphology.” They note that while the psychological and behavioral implications of overwork had been studied, imaging hadn’t been done to investigate the effects on brain structure. Indeed, they report: “These findings provide novel neurobiological evidence linking prolonged working hours to structural brain changes, emphasising … the long-term cognitive and emotional implications of overwork.”

The researchers concluded that overwork itself can contribute to brain changes, as can occupational stress and sleep deprivation that can result from being overworked.

So, if your workday often creeps up on 10 hours or more, these medical doctors call this a possible “occupational health concern.” And especially if you’re making consequential decisions—or you’re a consumer relying on a professional who does—understand the pressure, and the value of rest. Whether you’re making life-or-death judgment calls or just trying to help your team meet their performance goals, research like this literally shows how too much work can do more harm than good.

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