Depression is vexing, in no short part because doctors are themselves confused about the exact causes. But science hasn't let us down completely! Learn what's been proven to be a factor and what might be—understanding the triggers will help you get the best treatment.
If anybody tells you that they know definitively what causes depression—it doesn’t matter if they’re a medical professional, a well-meaning friend, or someone selling essential oils on social media—that person doesn’t know what they’re talking about. One thing we do know: Depression is not a choice and it has exactly zero to do with being weak-willed or lazy. Here, we’ll dive into what happens in your brain—and what triggers those brain changes—that can lead to the deep sadness of having depression. By understanding these factors, you can stop blaming yourself or trying to will yourself happy and, instead start showing yourself the empathy a friend would…an important part of the journey of feeling better.
Sometimes it seems like depression —a weeks-to-years-long stretch of sadness or hopelessness with symptoms like fatigue, sleep problems, a change in appetite, crying jags, and sometimes even suicidal thoughts—comes out of nowhere.Scientists would love to be able to pinpoint the exact cause of depression, but so far, research has only narrowed it down to biological changes in the brain triggered by a whole bunch of factors. These factors can be internal (like genetics, hormonal swings, chronic pain, even gut bacteria) or external (like childhood abuse, loss of a loved one, financial stress, or side effects of medication), and they can all work together simultaneously to make you feel like never getting off the couch again. Let’s dig further into the details.
A Chemical Imbalance (a.k.a. the Tip of the Iceberg)
Depression has been studied for ages. Hippocrates himself believed that melancholia—the pre-medicine name for depression—is caused by a buildup of black bile. Since then, more accurate methods of research have pinpointed an imbalance in brain chemistry. For the last 50 years, scientists have pointed to low levels of monoamine neurotransmitters that help regulate mood, digestion, sleep, and other body functions. Doctors aren’t sure what causes these low levels, but they know that antidepressant drugs seem to raise them and make people feel better.
Most medications used today to treat depression operate on this theory, targeting neurotransmitters like norepinephrine, dopamine, and especially serotonin. Even though these drugs are still the most effective first-line treatment, many scientists think of “chemical imbalance” as shorthand for what’s really happening—a more complicated mechanism where neurotransmitters are just part of the story.
Other Causes of Depression
The truth is, some people are at a higher risk of depression than others for several possible reasons, including:
Family History of Depression
Your risk for developing __MDD__ (Major Depressive Disorder, also known as clinical depression) is higher if members of your family have been depressed. But, much like if your family is comprised of Mensa members or ukulele masters, it’s difficult to tell how much of that is due to genetics and how much is due to environmental factors (for example, three hours of mandatory ukulele practice every night).
There is no single gene for depression. A British research team studied more than 800 families with recurrent depression and isolated a chromosome called 3p25-26 that looks promising as a possible genetic link. But another recent British study examined associations between 18 previously studied genes that were thought to be candidates for inherited depression, and found zilch, zero, nada connection. Still, genes are likely to be another piece of the puzzle, and multiple genetic variations are probably involved.
One reason this stuff is so hard to study is that scientists can’t just separate identical twins at birth and see who ends up depressed. That’s totally unethical. The next best thing is to study families and compare identical twins to fraternal twins—the theory being that if depression is genetic, it would show up more in identical twins than in the fraternal type, who share just half their genes (the same as any other sibling).
Scientists who have done these types of experiments place the genetic risk for depression at about 40 percent. That means that even if depression runs in your family, it’s not necessarily your destiny. The remaining 60 percent of depression risk is an emotional crapshoot of other factors, like personal history, social relationships, and environmental circumstances.
Little kids are particularly vulnerable to maltreatment and trauma since their brains are still developing, along with their confidence and self-esteem. This trauma doesn’t need to be shocking or violent, though it can be. Abuse (physical, sexual, or emotional), parental neglect, or growing up in a home with an alcohol or drug addict can all leave lasting scars that are linked to depression. Even tough circumstances that don’t measure up to “abuse”—like the loss of a loved one or a nasty divorce—can trigger depression. According to research, 75.6% of chronically depressed patients report clinically significant histories of childhood trauma.
Early life trauma can alter a person’s stress set points, inflammation, brain connections, and a bunch of other factors. It even appears to change the structure of developing brains in a way that predisposes people to depression. Not just any depression, but severe and recurrent depression, research shows. Using MRI scans, scientists discovered that these people have a smaller surface area to their insular cortex, which is the part of the brain responsible for self-awareness and emotional regulation.
All this means is it’s more important to be mindful about past trauma. Burying the events and trying to avoid emotionally processing them isn’t going to make them go away. In fact, these feelings are likely to grow into (untrue) beliefs that you are unworthy and unsafe in the world, and an inability to trust other people. If you have negative self-beliefs like this, talking with a therapist can help you separate the fact from the fiction and put things into perspective.
The connection between chronic stress and depression shouldn’t be a huge surprise to anyone who has experienced them. The research backs it up—stressful life events—such as (but not limited to) trauma, death of a friend or family member, an ongoing bad relationship, constant pressure at work or school, caring for aging parents, even reports of terrorism in the media—can activate the hypothalamic-pituitary-adrenal (HPA) axis to spit out extra cortisol. Studies have shown that chronic stress and chronically jacked-up cortisol levels may be responsible for depression.
Some integrative physicians and naturopaths hypothesize that constant exposure to stress—and the body’s fear response, which can make you feel like you’re walking through a haunted house…all the time—can overload the adrenal glands. This condition is called adrenal fatigue, though diagnosis is still controversial among endocrinologists. It isn’t depression, but it looks a lot like the symptoms of depression.
There’s a huge amount of overlap between neuroplasticity changes (how the brain tweaks its neural pathways and synapses) caused by pain and depression. That means the two conditions can make each other worse, leading to a frustrating cycle of hurting and hopelessness. Research shows that chronic pain, which is a state of stress, often induces depression. On the flip side, studies reveal that up to 85 percent of people with chronic pain are also depressed, which sounds shockingly high—but not when you consider that pain and mood regulation travel on the same pathways. Think of it as a yellow brick road that leads to Ow and Ugh instead of Oz. These areas of the brain include the insular cortex, prefrontal cortex, anterior cingulate, thalamus, hippocampus, and amygdala.
Other Medical Conditions
As if being sick wasn’t difficult enough, certain physical illnesses like to bring their sidekick, depression, on a ride-along, including the likes of:
Vitamin B12 and folic acid deficiency,
Coronary heart disease
Traumatic brain injury
Their relationship can start a bunch of ways. A serious health issue can change a person’s life in ways that spark depression. Certain conditions (like Parkinson’s, stroke, and traumatic brain injury) create chemical or physiological changes in the brain that lead to depression.
Some research has even found depression to be an early indicator of physical illness in the case of Alzheimer’s, Parkinson’s, Cushing’s syndrome, Wilson’s disease, cardiovascular disease, and others.
No matter which came first, the depressed chicken or the pained egg, research shows that people dealing with serious illness and depression are more likely to have more severe types of both conditions. And you don’t need a Ph.D. to see how depression might prolong a sick person’s recovery time and overall results.
Medications That Can Contribute to Depression
Now, another possible cause of depression: medication. You’d think a sick person taking their medicine would be a win-win, but some treatments are linked to the onset of depression. Among them are:
Blood pressure drugs including beta-blockers and ACE inhibitors
Antidepressants like Zoloft (sertraline), Celexa (citalopram), Wellbutrin (bupropion), and Elavil (amitriptyline)
Anti-anxiety drugs such as Xanax (alprazolam), Klonopin (clonazepam), Valium (diazepam), and Ativan (lorazepam), plus sedatives like Ambien (zolpidem)
Corticosteroids like prednisone, taken for rheumatoid arthritis, lupus, asthma, allergies, or other conditions
Acid reflux drugs—think proton pump inhibitors like Prilosec (omeprazole) and Nexium (esomeprazole) and antacids like Pepcid (famotidine)
Anticonvulsants prescribed for variety of reasons, such as epilepsy, bipolar disorder, migraines, and nerve pain; these anticonvulsants include Neurontin (gabepentin), Topamax (topiramate), and Lamictal (lamotrigine)
Hormonal birth control and hormone therapies like estradiol, Proscar or Propecia (finasteride)
Women are nearly twice as likely as men to be diagnosed with depression. Though scientists aren’t sure exactly why that is, they might be more comfortable taking their symptoms to a doctor, they go through significant hormonal fluctuations, and they’re the victims of more violence and psychological aggression by intimate partners and sexual assault.
And there’s no denying that certain types of depression are primarily lady-centric territory, regardless of how you identify: Premenstrual Dysphoric Disorder (PMDD), Peripartum Depression (PPD), and Perimenopausal Depression are all linked to dramatic hormonal changes in a woman’s life.
Risk Factors That Could Be Linked to Depression
Instead of pointing to these as “causes” of depression, let’s all agree that these factors are linked to depression until scientists figure out the mechanisms behind depressive disorders. Here, we dig further into the details of several factors that could play a role in depression.
Sleep issues. A bad night’s sleep might leave you slumped over your cold-brew coffee by lunchtime, but a consistent lack of sleep can turn you into a shell of yourself. (Just ask a new parent. Or someone who lives near an airport.) A big symptom of depression is having a hard time getting to sleep and staying asleep. As it turns out, research shows that people with insomnia have double the risk of developing depression as people without sleep problems.
Unemployment. Americans can get so wrapped up in work that it becomes part of their identity. Losing your job can be a blow to your self-esteem and chip away at your sense of purpose. Research shows that the longer people are unemployed, the more likely they are to be depressed. Twice as likely (12.4%), in fact, as those with full-time jobs (5.6%). When you’ve been unemployed for more than six months, the rate of depression jumps to 18%.
Loneliness.Loneliness is a strong risk factor for depression, and it’s a growing epidemic. Despite smartphones and social media’s unprecedented power to connect us, a recent Cigna survey reveals that nearly half of Americans feel left out, alone, and socially isolated. Gen Z are having a particularly hard time, with the highest loneliness score of all the generations.
A Lousy Diet. It shouldn’t be a big surprise that people’s brains work better when they eat nutritious, high-quality fuel. Research shows that folks who eat too much sugar are more likely to get depression, but scientists aren’t sure whether it’s due to the sugar (and dopamine) highs and lows, chronic inflammation, or some other mechanism. Conversely, people who eat a healthy Mediterranean diet, with tons of fruits, vegetables and fish, are less likely to develop depressive symptoms in older age.
Weight. Depressed people are more likely to be obese than people who aren’t depressed. A recent meta-analysis analysis of data from almost 46,000 people found that weight loss, nutrient boosting, and fat-reduction diets can all decrease the symptoms of depression, even in people without clinically diagnosed disorders.
Inflammation. There’s a growing theory among researchers that inflammation may play a role in a percentage of depression cases that don’t respond well to anti-depressants. There’s research showing why targeting the immune system might be a good plan: People with depression have elevated markers of inflammation compared to non-depressed people, studies show. And a recent analysis showed that anti-inflammatory aspirin, statins, and antibiotics actually curbed the depressive symptoms in some people.
Gut Bacteria. A decade ago, studying your gut microbiome for signs of depression might have sounded like reading tea leaves, but today, there’s enough research on the microbiota-gut-brain axis to get scientists on board. Your microbiome can produce or promote production of neurotransmitters like serotonin, GABA and dopamine. Those neurotransmitters help regulate bacterial growth, and—going along with the inflammation theory—the suspicion is they can play a role in curbing depression, too. A recent analysis found that people who lack certain bacteria (called Dialister and Coprococcus—they sound like demons you can conjure from a musty leather book) are more likely to experience depression. Of course, research is ongoing.
Social Media. We’ve all seen alarming headlines about how endlessly scrolling through Instagram causes FOMO and depression, so it’s normal to worry about your kids (or yourself) being glued to your phone. But the link is more complicated than just how much screen time you rack up. How you spend your time on social media matters. Using it to connect with friends near and far or seek out information is all good. Negative social media behaviors—like comparing yourself to others and deciding you don’t measure up or getting anxious over being tagged in fugly photos—do correlate with higher rates of depression, according to recent research.
As you can see, no one is 100% sure of the exact causes of clinical depression yet. But what’s important to note is that we don’t need to know in order to alleviate the symptoms. Effective treatments for people with depression are available today.
Frequently Asked QuestionsDepression Causes
If depression runs in my family, does that mean I’ll pass it on to my child?
Look, we won’t lie to you—scientists have found that a child’s risk of developing clinical depression later in life is higher if depression runs in their family. But just because there’s a link doesn’t mean it’s written in stone. The research says that genes are responsible for less than half of depression risk, and the rest is external triggers. There’s no one gene for depression. In fact, there’s not even a clear pattern of inheritance! So let’s concentrate on this: There’s no reason to think your child will experience depression, but if they do, you’ve got the tools to help them, make recovery easier to find, and erase any shame they may feel.
Could my depression medications be making me more depressed?
In a crappy catch-22, yes, it’s possible. Rx pills that change the chemistry in your brain can lead to depression, so it does make sense that medications aimed to help with depression fall into this category, as ironic and mind-boggling as it may seem. It’s important to report any negative side effects to your psychiatrist so that if one drug isn’t working, you can try another—and, remember, there are so many different antidepressants available. While you may go through a frustrating period of trial-and-error to figure out which one or which mix is best for you, finding the right option will be worth it.
Can depression be contagious?
Nah. Look, everyone knows a Debbie Downer whose buzzkill energy can destroy a room’s vibe. They may insist they’re just keeping it real, but all that pessimism can rub off after a while. A recent study even backs it up—researchers found that moods can actually spread through social networks like an emotional flu. That means if you hang out with happy people who laugh a lot, you might find yourself giggling after a while. Or if you spend time with annoyed, frustrated people, you’ll likely feel more annoyed and frustrated afterward. However, the study did not find any evidence that these fleeting bad moods blossom into full-blown depression, or that people can pass on depression this way. Long story short, it’s true that bad moods can spread for a short time, but if you’re around someone who’s depressed a lot, you won’t “catch” it.
Does social media cause teen depression?
The time teens spend on social media has skyrocketed by 62.5% since 2012, according to a recent eight-year study, and there’s no sign of it slowing. (FYI, they’re at about 2.6 hours per day.) Rates of teen depression are up, so it’s tempting to blame social media, but—despite some alarming headlines—the facts don’t entirely match up. The same study found the amount of time spent on social doesn’t correlate with the risk of depression. That said, other studies have shown links to depression and social media, but it’s hard to form a causal relationship. Since social media can be used a bunch of different ways—some of which are very positive, like connecting with friends and seeking out information—that makes a lot of sense. So, while it’s true that in-person socializing does boost mental health, that doesn’t necessarily mean the opposite is true for online socializing.
Diet and Depression (2):Scientific Reports. (2017). “Sugar intake from sweet food and beverages, common mental disorder and depression: prospective findings from the Whitehall II study.” nature.com/articles/s41598-017-05649-7#Sec8