7 Surprising Causes of Depression

Most of us can name the usual triggers for depression without much thought: a sudden trauma, the death of someone close, a layoff, money trouble that won't let up. These are real, and they're familiar. But depression is also the leading reason people between the ages of 15 and 44 end up disabled, which is reason enough to look past the obvious. Knowing the quieter, stranger causes gives you a better shot at heading the whole thing off before it takes hold.

Take Seasonal Affective Disorder. When people picture a season dragging their mood down, they picture gray, cold winter days. SAD does hit hardest then for most patients. A smaller group, though, slides into it during summer. The theory is that the summer version has less to do with the heat itself and more to do with abrupt changes in weather patterns throwing the body off.

Nicotine is a strange one. It's classified as a stimulant, and ordinarily it nudges serotonin and dopamine levels upward, which is why smokers often report feeling steadier after a cigarette. In that respect it behaves a lot like an antidepressant. But the brain doesn't respond uniformly. For certain people, nicotine (and, oddly, actual antidepressant drugs) produces the reverse effect, pushing mood down instead of lifting it.

There's also vitamin D. Low levels of it track alongside a long list of health problems, depression among them. What researchers haven't pinned down is the direction of the arrow: does the deficiency bring on the depression, or does being depressed lead to the deficiency? Either way, people running low on vitamin D tend to report the kind of fatigue and muscle pain that overlaps with depressive symptoms.

Then there's the sheer amount of time we spend online. Email, social feeds, shopping carts, bill paying, aimless scrolling. Hours disappear into it daily, mostly on autopilot. Some research points to a connection between heavy internet use and moderate to severe depression. Whether it's a particular kind of use doing the damage or just the volume of it, nobody can say yet. That part needs more study.

A less expected one: the end of a long-running show or film series. People get genuinely attached to the things they watch over and over. A series that's been on for years with a devoted audience, something like Friends, or a string of movies like the Harry Potter films, builds a kind of standing company in a person's week. The characters start to feel like people you know. When the final episode airs or the last installment hits theaters, that comfort vanishes, and for some viewers it registers as losing a friend.

Where you live factors in too. People in rural areas tend to report depression less often than people in big cities. The pace probably has something to do with it. City living keeps the stress-regulating part of the brain running hot, and once it's that active, dialing stress back down gets harder.

Siblings matter more than you'd guess. Teenagers who don't get along with their brothers and sisters carry a higher risk of depression later, and the effect shows up more strongly in men. The thinking is that siblings are an early practice field for socializing. Fail to click with them and you may struggle to click with people out in the world. Weak social and communication skills can lead straight to depression, because they get in the way of building the relationships that make life feel worth something.

Depression doesn't look the same on any two people, and it ranges from a mild drag to something fully disabling. Given how much it can cost someone, learning the full spread of causes, including the ones nobody warns you about, is the groundwork for any real plan to avoid it.

Rosemary Kitchen