Pop quiz: What’s the leading cause of disability among US adults—the one almost every American will experience at some point in his or her lifetime? If you said depression, well, you probably read the headline of this story. Good job.

At any given time, depression affects about 5% of the population, or approximately 15 million Americans, according to the Anxiety and Depression Association of America. Despite its prevalence, doctors aren’t sure exactly what causes it or how it will present itself from one sufferer to the next.

Of course, there are some well-established triggers—stuff like a super stressful life event or disorders that affect your brain or mood. But there are also some surprising, mysterious depression correlates that most people would never suspect.

Your Carb-Heavy Diet

OK, maybe not all carbohydrates. Many types of carbs—such as vegetables and fruit—are great for you. But refined carbs—stuff like chips, cookies, and soda—are bad news. Studies have linked diets high in refined carbs to breast cancer and heart disease. And now science says refined carbs may also play a part in depression.

When researchers reviewed data from 70,000 postmenopausal women, they found a significant link between those who ate diets high in refined carbs and those who had new-onset depression. “Refined foods such as white bread, white rice, and soda trigger a hormonal response in the body to reduce blood sugar levels,” the study authors say. “This response may also cause or exacerbate mood changes, fatigue, and other symptoms of depression.” Cut out refined carbs, and you could lower your risk for depression, the study suggests.

You Have A Middle-Management Job

Reason to feel better about being stuck on the bottom rung of the corporate ladder: A recent study from Columbia University finds supervisors and managers are more likely to be depressed than the people above or below them.

After reviewing data from more than 20,000 workers, the researchers found 17% of those in a middle management job reported having anxiety or depression, compared to only 12% of those in bottom-tier roles. When you’re sandwiched in the middle of the corporate hierarchy, you have few opportunities to make decisions that affect your company, while at the same time you’re saddled with hefty job demands and responsibilities. All of this could kindle stress and lead to depression, the study team says. (The Power Nutrient Solution is the first-ever plan that tackles the root cause of virtually every major ailment and health condition today.)

Your Thyroid Is Acting Up

While an under- or over-active thyroid is often associated with unwanted weight gain or loss, a haywire thyroid can cause more than just weight swings. It has also been associated with problems like thinning hair, constantly feeling chilly, and—you guessed it—depression. Research has gone back and forth on just how much a malfunctioning thyroid can affect your mood, but new evidence backs up the idea your thyroid’s plays a part in depression.

How? Since the thyroid secretes hormones that regulate metabolism, it affects every organ in your body, including your brain. Experts say some depression sufferers may benefit more from thyroid hormone medications than from depression meds.

You watch the local news every morning, and your monitor trending news online. That’s a good thing, right? Well, not always. While keeping up with current events can make you more fun around the water cooler, research suggests it could be a catalyst for depression. The problem? The news stories we tend to consume aren’t happy-go-lucky tales of long-lost lovers reunited after 50 years, or cute kids who end up on daytime TV because of a YouTube video gone viral. The news is mostly plane crashes, burning buildings, car accidents, and war. Some media studies have found bad news outweighs good news 17 to 1.

Spend too much time focusing on the bad stuff going on in the world, and it can make the world seem like a bad place. And, surprise surprise, that can make you feel depressed.

But no, you don’t need to ditch your newspaper, TV, and the Internet altogether. Instead, try tweaking your media consumption so you get a healthy dose of happy news stories to counteract the sad stuff.

You Spend Way Too Much Time On Facebook

You’ve heard social media may be making you narcissistic, sad, and is otherwise ruining your life. This is kind of one of those stories. Social media can be a productive way to keep in touch with family and friends, and to catch up with the (hopefully not-too-sad) news. But studies have also shown a link between spending too much time on Facebook and feeling depressed.

Is Facebook itself causing depression? Probably not. But if you’re sitting at work or lazing on your couch, browsing through a highlight reel of your friends’ post-worthy events—perfect family photos, vacation selfies, artistic food photos taken at fancy restaurants—can bring on or worsen depressive symptoms, especially if you’re doing it all day every day, suggests research from the Journal of Social and Clinical Psychology.

The solution: Spend less time on your social networks and more time actually socializing. Chatting or hanging with friends is a proven depression lifter. And when you do jump on Facebook, remember your friends’ pages reflect the times they are happiest, not their everyday lives.