And that is driving people nuts, he says. "After awhile, if you do that the whole day long, you get this vague feeling that you're not done. And that you're never done. And that when you go home, you're still not done." And science has proved, he says, that behavior produces a kind of stress called "learned helplessness."
"As soon as you have that type of stress, you can actually show that people don't do math problems very well, they can't perform very well on memory tests," he says. "There's a whole range of cognitive gadgets in the brain that begin to collapse, if you feel like you're not getting anything done. And I'm convinced that half the work force is experiencing that on a weekly basis. In fact, I even have a name for it: the Sunday Evening Blues."
This means you may be able to ratchet down the pace over the weekend, even sleep in on Saturday (and lack of sleep is another issue with Medina, one he says just pummels the brain -- but that's a story for another day). Late Sunday night, though, the pressure creeps back.
"On Sunday night, your brain is darn well aware that pretty soon you're going to hit the firewall again, or that it's going to hit the fan, and come Monday morning it starts all over again."
And that is particularly true for America's children, whose schooldays are often tightly structured and completely time-pressed.
"It's one of the biggest contributors to stress," says Denise Pope, a lecturer at Stanford University's School of Education, and the founder of the university's Stressed Out Students program. "If you're running around, period to period, every 50 minutes, with three to five minutes of 'passing time' in between, you are literally on a crazy treadmill all day long."
And the school day, for most students in the United States, doesn't end there. Many have as much as three, four or five hours of homework at night. If children's hours were governed by federal regulators, fines might be in order.
Pope started her organization after finding that research backed up her own concerns about the stress students are experiencing: more seeking mental health services, more cheating, more suffering severe anxiety. One survey found that 460 parents in two California school districts cited school-related stress among the top concerns for their children.
And many teachers are growing concerned, too. At the most recent Stressed Out Students national conference, one educator noted that "school for many kids is not a place to learn, but a place to perform. We need to begin to change the culture so our youth can take joy in learning."
Pope agrees. "We know kids learn better when there's time to sit and focus and reflect, really reflect on a subject, in depth," she said.
She and her colleagues recommend that school districts reconsider having students cover more than two or three subjects in a day. Better, they believe, to have longer periods for single subjects, and work on homework while still in the classroom, while the lessons are still in their heads. And if a teacher feels the need to assign work for the student that night, it should never be busy work. It should be assigned sparingly, as a way to reinforce the lessons taught earlier in the day.