What Are the Causes of Depression? Here Are 14 Surprising Triggers You Should Know About

Seasonal Changes

Seasonal affective disorder (SAD) is a type of depression that's related to changes in seasons. SAD begins and ends at about the same times every year, typically lasting four to five months per year, the National Institute of Mental Health reports.

About 5% of people in the US have SAD, according to the American Psychiatric Association. While the disorder is most commonly associated with the winter season, some people do experience it during the warmer months.

Warm weather depression arises when the body experiences a "delay adjusting to new seasons," Alfred Lewy, MD, professor of psychiatry at Oregon Health and Science University, tells Health. Instead of waking and enjoying dawn, the body has a hard time acclimating, he says, which could be due to imbalances in brain chemistry and the hormone melatonin.

Smoking

Researchers recently analyzed 148 studies and found that while nearly half of the studies showed that depression led to smoking, over a third found evidence that smoking led to depression. So the exact association is still unclear.

Once you stop smoking, your body has to get used to not having nicotine. This period, known as withdrawal, can be accompanied by sadness, irritability, and mood changes. Quitting smoking has also been linked to an increase in depression, but researchers have found that the depression may tend to improve as you stick to your abstinence from cigarettes.

Thyroid Disease

When the thyroid, a butterfly-shaped gland in the neck, doesn't produce enough thyroid hormone, it's known as hypothyroidism—and depression is one of its symptoms, according to the Mayo Clinic. Generally, the more severe the thyroid disease, the more severe the mood changes. Depression due to hypothyroidism may also become more serious over time.

Researchers have said that, based on the evidence, it's reasonable to screen for thyroid dysfunction in patients with depression. If you experience new depression symptoms—particularly along with other symptoms of an underactive thyroid, such as cold sensitivity, constipation, and fatigue—a thyroid test couldn't hurt. Hypothyroidism is treatable with medication.

Poor Sleep Habits

It's no surprise that not getting enough sleep—or enough good sleep—can lead to irritability. But it could also increase the risk of depression.

Insomnia, aka, having trouble falling or staying asleep, is one sleep disorder that has been linked to depression. Hypersomnia—feeling extremely sleepy during the day—and obstructive sleep apnea—when you involuntarily stop breathing for brief periods of time during sleep—have also been shown to be associated with depression.

"If you don't sleep, you don't have time to replenish [brain cells], the brain stops functioning well, and one of the many factors that could lead to is depression," Matthew Edlund, MD, director of the Center for Circadian Medicine, in Sarasota, Florida, and author of The Power of Rest, tells Health.

Social Media Overload

Spending too much time on social media? A number of studies now suggest this can be associated with depression. A 2020 systematic review found that the prolonged use of social media, as well as constantly checking your own social media profile and using social media more passively (reading posts) than actively (making posts), can cause depression.

Using four or more social media platforms, feeling an intense emotional connection to social media, and/or feeling as though you are addicted to social media are all associated with an increased risk of depression.

"You just want to limit the time you engage with it, so that you're not constantly checking in to see what the latest most outrageous news is or the latest social media battle is about," Lily Brown, PhD, director of the Center for the Treatment and Study of Anxiety at the University of Pennsylvania, previously told Health. "Some amount of engaging with that material is fine, but for many people it can be a tremendously triggering experience to look at social media or to read the news." If that's the case, Brown says, "You need to be really thoughtful of whether it would make sense for you to limit your exposure."

The End of a TV Show or Movie

Reaching the final episode of a TV show or the end of a movie triggers depression in some people. For example, back in 2009, some Avatar fans reported feeling depressed and even suicidal because the movie's fictional world wasn't real. There was a similar reaction to the final installments of the Harry Potter movies, according to Entertainment Weekly.

"People experience distress when they're watching primarily for companionship," Emily Moyer-Gusé, PhD, assistant professor of communication at The Ohio State University, tells Health. With Avatar, Moyer-Gusé suspects people were "swept up in a narrative forgetting about real life and [their] own problems."

The ends of a large-scale projects, such as a big home renovation, or the end of an experience like a vacation, can also result in depression.

Where You Live

Whether city or country life is better is an endless debate. But research has found that those living in urban settings do have a 12–20% greater risk of depression than those in less populated regions. This may be due to the physical factors that come with living in an urban area, including higher rates of environmental pollution and noise pollution (like cars honking), as well as the city's design (for example, tall buildings that wall you in), and rates of accidents and violence, according to a 2017 study.

The same study also found that living in neighborhoods that are poorer, that have residential ethnic segregation, and with less access to green space or places to walk can also contribute to depression.

Having Too Many Choices

The sheer number of options available—whether it's how to save, where to live, or what to buy—can be overwhelming. That's not a problem for those who pick the first thing that meets their needs. However, some people respond to choice overload by exhaustively reviewing their options in the search for the very best option. Research suggests that this coping style is linked to perfectionism and depression.

It is a topic that psychology professor Barry Schwartz first made waves about more than a decade ago in his book The Paradox of Choices. In it, he wrote that having too many choices "can make you question the decisions you make before you even make them, it can set you up for unrealistically high expectations, and it can make you blame yourself for any and all failures. In the long run, this can lead to decision-making paralysis, anxiety, and perpetual stress. And, in a culture that tells us that there is no excuse for falling short of perfection when your options are limitless, too much choice can lead to clinical depression."

What You Eat (Or Don't Eat)

A regular diet that contains added sugar, soda, and junk food was associated with increased risk of depression, according to a 2020 study published in the International Journal of Environmental Research and Public Health. Eating high quantities of food that cause inflammation, such as processed meats and alcohol, can also increase the risk. On the other hand, foods that have an anti-inflammatory effect, such as nuts and olive oil, can also reduce the odds of depression, according to research.

"Omega-3 fatty acids from seafood and monounsaturated fats from nuts, avocados, and olive oil appear to be particularly important and beneficial to our mental and brain health," Felice Jacka, PhD, a food and mood researcher and president of the International Society for Nutritional Psychiatry Research, previously told Health.

Family Tension

Families can be, well, complicated, and strain in family relationships as we age can actually lead to depression in midlife. The more tension we have with our mothers, siblings, or spouses, the more likely we are to have symptoms of depression, according to a 2017 study.

Research on tension in spousal relationships isn't new, but midlife depression stemming from tension with family members is a novel area of study. The tension between siblings in midlife often stems from having to consider, prepare, and navigate their parents' care.

Birth Control Pills

Like any medication, the Pill can have side effects. Though uncommon, depression is a possible, and potentially serious, side effect of the Pill, according to MedlinePlus. The reason behind the link is still unknown, Hilda Hutcherson, MD, a clinical professor of obstetrics and gynecology at Columbia University, tells Health.

"It doesn't happen to everyone, but if women have a history of depression or are prone to depression, they have an increased chance of experiencing depression symptoms while taking birth control pills," Dr. Hutcherson says.

If you're taking oral birth control and experience depression, especially if you also have trouble sleeping, tiredness, loss of energy, or other mood changes, check in with your doctor, who might consider switching you to a different Pill version or another type of birth control.

Rx Medications

The Pill isn't the only medication that can cause depression; it's a side effect of many drugs. Heart drugs such as beta-blockers and calcium-channel blockers, cholesterol-lowering statins, anticonvulsants, opioids, and corticosteroids are some types of medications tied to depression, as Health previously reported. Read the potential side effects when you take a new medication, and always check with your doctor to see if you might be at risk.

Changes After Giving Birth

After having a baby, it's common for new moms to experience feelings of sadness and anxiety; this emotional response is often referred to as the baby blues. But in more serious cases, these feelings last longer than a few days and may be a form of depression called postpartum depression.

Studies estimate that postpartum depression affects 10%–15% of new mothers, but Kathleen Kendall-Tackett, PhD, a psychologist and lactation consultant who specializes in postpartum depression, previously told Health it may actually be as high as 25%.

Your Sex Life

The less sexually satisfied you are, the more at risk you might be for depression. Researchers published a study in the International Journal of Environmental Research and Public Health in 2020 that showed lower levels of sexual satisfaction in young adults are associated with significantly higher levels of depression, regardless of whether they are in a relationship. Those who had higher levels of sexual satisfaction had lower levels of depression.

The authors of that study say that their findings suggest that "sexual satisfaction is relevant to the mental health status of adolescents and young adults, and sexual problems can lead to anxiety and depression."

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