Call it “the blues,” “a funk,” or “waking up on the wrong side of the bed,” we've all felt it at one time or another: For no particular reason, you feel sad or anxious for a day, a week, maybe even several weeks. Muddled thoughts and low energy slow your productivity and wreak havoc on your days. You scour your brain to try to pinpoint what's bothering you, but come up empty.

Americans today fill more than 232 million prescriptions annually for antidepressants — up fourfold from a decade ago. But as rates of both clinical depression and more transient day-to-day mood problems climb, some mental health experts say evaluating diet, lifestyle choices, and your attitude could be key in kicking a persistent bad mood. “Consider your symptoms a wake-up call,” says psychiatrist James Gordon, MD, author of Unstuck: Your Guide to the Seven-Stage Journey Out of Depression (Penguin, 2008). “Something in your life is out of balance.”

It isn't just a hunch that these factors play a role: For decades scientists have believed that depression arises from deficiencies (some of them genetic) in brain chemicals like serotonin. But researchers now realize that blue moods can also be a product of an unhealthy brain structure made up of withering brain cells that, consequently, have trouble communicating. One primary factor that contributes to cell atrophy? A poor diet, says Alan C. Logan, ND, author of The Brain Diet (Cumberland, 2007). Here are five dietary factors and other lifestyle habits that can mess with your mood.

  1. Skipping breakfast. Do you start your day by scarfing down a bagel in the car — or with no breakfast at all? Not fueling your body in the morning will only backfire, Logan says. Blood sugar dips, sending your body into fight-or-flight mode. This drenches your system in stress hormones — such as cortisol and adrenaline — that interfere with mood and thinking. If you have simple carbs, like a white bagel, you get a fleeting lift but then crash even harder than if you'd eaten nothing. A study published in Appetite divided teens into four groups, with two groups eating a high-fiber cereal, one slugging a pure-sugar drink, and another skipping breakfast. When tested later, those who ate no breakfast saw their scores for “contentment and alertness” drop precipitously throughout the morning. Those who had the sugary drink saw their scores spike and then crash 90 minutes later, with mood plunging by morning's end.