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- Depression develops from a combination of factors—genetics, life stress, mental health history, and environment—not a single cause.
- Everyone has a different threshold for depression based on their vulnerability and stress levels; understanding yours helps you protect against it.
- Women, young adults (18-25), multiracial individuals, and LGBTQ+ people face the highest risk due to biological and social factors.
- Real connections, quality sleep, regular movement, and brain-healthy foods can all help reduce your risk.
- Early professional help makes a difference. Therapists and psychiatric providers offer evidence-based tools that significantly reduce severity and duration.
You’ve probably wondered why you feel this way or why it’s so hard to shake. Maybe you’ve heard it’s about brain chemistry, or stress, or genetics. But depression doesn’t have a single cause, and that’s important to understand.
Depression develops from a mix of factors: your biology, life circumstances, mental health history, and environment. Understanding which factors affect you can help you and your provider treat it more effectively. Here’s what research shows about the main contributors and what you can do to protect your mental health.
What is the leading cause of depression?
Depression doesn’t have a single cause. It develops when predisposing factors (like genetics or brain chemistry) combine with life stressors (like trauma, major changes, or chronic stress).
Think of it like a tipping point. Whitney McSparran, a licensed professional clinical counselor at Thriveworks, explains it this way: “Everyone has a threshold where their vulnerability meets stress, and that combination can trigger depression. That threshold is different for each person.”
Some people have a lower threshold because of their genetics or biology—they’re more vulnerable. Others have a higher threshold but experience extreme stress that pushes them past it. This is called the diathesis-stress model: predisposition plus life events.
Your threshold depends on:
- Your genetic makeup and brain chemistry (predisposition)
- Current stress levels and major life events
- Available support systems
- Coping skills and resources
Expert insight
“Each person has a point at which their predisposition and stressors collide and can present as depression. This threshold is different for everyone.”
—Whitney McSparran, LPCC
Breakdown of the main causes of depression
The causes of depression are widespread and affect many areas of life. Most commonly, depression causes and risk factors fall into the following categories:
| Category | Examples | How it contributes |
|---|---|---|
| Biological | Genetics, hormones | Affects mood regulation; risk increases up to 50% with family history |
| Psychological | Pre-existing mental health conditions, trauma/abuse, stressful life events | Reduces emotional resilience and increases stress response |
| Medical | Chronic illness, life-threatening conditions, substance use | Can directly impact brain chemistry or increase anxiety and daily stress |
| Environmental | Unsafe housing, social isolation, seasonal changes, natural disasters | Eliminates sense of safety; makes stress management difficult |
Biological factors
1. Genetics and family history
Genetics play a significant role in depression. Having a family history of depression can make you up to 50 percent more likely to develop it yourself. This connection comes from both inherited genes and shared environmental factors within families.
2. Hormonal changes
Hormonal shifts—especially after childbirth—can trigger depression. Peripartum depression affects many new parents and can sometimes develop into long-term depressive disorders.
3. Brain chemistry (what we used to think vs what we know now)
For years, depression was blamed on low serotonin levels, which is why SSRIs (selective serotonin reuptake inhibitors) became a primary treatment. Recent research has challenged this oversimplified view: Serotonin deficiency alone doesn’t cause depression. However, SSRIs and similar medications still work effectively for many people, likely by affecting multiple brain systems beyond just serotonin.
Psychological factors
1. Pre-existing mental health conditions
Conditions like anxiety, ADHD, or schizophrenia can worsen depressive symptoms by increasing stress levels and making everyday functioning more difficult. Low mood and low self-esteem become harder to manage when you’re already dealing with another mental health condition.
2. Trauma and adverse experiences
Traumatic experiences can severely impact stress levels, self-esteem, and overall mental health. These experiences create lasting effects that make you more vulnerable to depression.
3. Substance use disorder
Research shows that substance use disorder (SUD) can significantly increase the risk of developing depression. This relationship works both ways: While SUD can cause depressive symptoms, depression can also increase the risk of developing SUD.
4. Major life changes and loss
Life changes like being diagnosed with a terminal illness, the death of a family member, long-term financial stress, divorce, or job loss can erode emotional resilience over time. Loss in any form increases feelings of sadness, hopelessness, and despair, and makes caring for yourself more difficult.
While depression symptoms caused by grief aren’t the same as a depressive disorder, if those symptoms persist for two months or more, you may be diagnosed with a depressive disorder.
“Stressful life events are often the most common catalyst for depression that I observe in my work as a therapist,” says Jami Dumler, a licensed clinical social worker at Thriveworks. “They’re frequently compounded by lifestyle factors such as diet and exercise, as well as family history that may create a predisposition to depression.”
Medical factors
Factors like being diagnosed with a physical illness or experiencing other bodily changes can seriously influence mood and self-perception and make it easier for depression to take hold.
1. Childbirth and body image changes
Childbirth causes a myriad of changes to your hormones and your body, often making your own body feel unfamiliar. Changes to body image can trigger low self-esteem and increased stress, opening the door for depression.
2. Chronic and life-threatening illnesses
Physical illness—especially chronic or life-threatening conditions—can lead to depression. Diseases like diabetes and thyroid disorders can impact brain chemistry, sometimes directly causing depression rather than simply putting you at risk.
Other chronic illnesses may not directly cause depression, but they increase stress levels and make daily functioning and self-care difficult, which contributes to depressive symptoms.
Environmental factors
Your environment has a strong impact on your mood and ability to regulate emotions.
1. Unstable or unsafe housing
In cases where housing or home life is volatile or unstable, people can feel unsafe in their own homes. Without a safe place to retreat to, stress becomes very hard to manage and can feel like a constant state.
2. Social isolation
An excess of alone time or isolation can also put stress on you. “Humans are herd animals; we evolved to exist in the type of interconnected community few of us get to experience today,” McSparran says. “In my practice, social isolation is the risk factor I see most consistently in people with depression.”
3. Seasonal changes
Seasons can also affect your environment, causing seasonal depression through their impact on levels of Vitamin D, melatonin, serotonin, and more.
Though these are some of the main causes of depression, unique, highly personal factors may also contribute to the development of a depressive disorder.
Key finding
“In my practice, social isolation is the risk factor I see most consistently in people with depression.”
—Whitney McSparran, LPCC
Common triggers vs underlying causes
Though many factors contribute to depression, there’s an important distinction between underlying causes and triggers.
Underlying causes are long-term factors that make you more vulnerable:
- Genetic predisposition
- Chronic hormonal dysregulation
- Neurotransmitter imbalances (like serotonin or dopamine)
Triggers are specific events or circumstances that can activate depression:
- Death of a loved one
- Job loss
- Chronic illness diagnosis
- Childbirth
“A risk factor is something that makes you more likely to experience depression, such as family history, brain chemistry, substance use, or social isolation,” McSparran says. “A trigger is a stressor that contributes to or sets off a response like depression, such as a breakup, toxic work environment, or relational conflict.”
“I describe this difference as passive vs. active,” Dumler says. “A risk factor is a passive characteristic or predisposition that may make someone more likely to develop depression compared to a peer without those risk factors. Triggers become active, specific events or factors that cause a depression episode.”
Do the causes of depression vary among age groups and gender?
Yes, while the core mechanisms of depression are similar across groups, specific risk factors and triggers vary significantly by age and gender due to biological differences, life stages, and social factors.
Take a look at some of the unique causes of depression affecting different age groups and genders:
Causes of depression in adults
Across groups of adults, there can be differences depending on group demographics—most prevalently, between certain genders. Below are depression causes commonly seen in women vs. men.
Causes of depression in women
Notably, women are two times more likely than men to be diagnosed with depression. The leading causes of depression in women can include:
- Hormone changes (due to reproductive cycles)
- Genetic predisposition
- Pre-, peri-, and postpartum challenges
- Job/life stress
- Experiencing sexual violence or harassment
- Eating disorders (which aren’t exclusive to women)
- Chronic anxiety
Causes of depression in men
Compared to women, men consistently report being lonelier and having fewer friends than their female counterparts. Other common causes of depression include:
- Societal pressure to repress emotions
- Low testosterone
- Body image issues
- Poorly developed ability to process difficult emotions
Each of these factors can leave men susceptible to depressive disorders and other conditions.
Causes of depression in older adults
For older adults, depression may be related to declining physical health or cognitive impairments. Examples of these factors include:
- Diseases like dementia or Alzheimer’s
- Cognitive decline
- Personal loss (deaths of partners/friends)
- Loneliness
- Physical health problems
- Anxiety over aging
Causes of depression in teens and young adults
Hormonal imbalances can cause significant mood shifts in teens of both sexes, but with budding social skills and self-esteem, teens are heavily affected by social factors. Common causes of depression for young people include:
- Genetic predisposition
- Academic stress
- Excessive media use (like social media)
- Bullying
- Body image issues
- Chronic fatigue
Causes of depression in children
A child’s environment is very influential over their mental health, leading environmental and social factors to be a driving force behind depression. Common reasons for the development of depression in children include:
- Unstable home environment (divorce, constant moving, abuse)
- Trauma
- Genetic predisposition
- Poor lifestyle habits (poor diet, lack of physical activity, insufficient sleep, excessive media exposure)
- Bullying
- Pre-existing or family history of psychological conditions (anxiety, ADHD, dyslexia, autism)
Who is most at risk for depression?
Young adults (ages 18-25), women, people of multiple races, and LGBTQ+ individuals face the highest risk for depression.
In 2021, the Centers for Disease Control and Prevention found that people ages 18 to 25 were most likely to suffer from major depression. The same dataset highlighted that those of two or more races were nearly twice as likely as other racial groups to develop depressive symptoms.
People within the LGBTQ+ community also suffer from an elevated risk of depression. These three groups are most at risk for experiencing depression due to unique social and psychological factors:
- Young adults commonly go through significant life transitions as they explore romantic relationships, career changes, social groups, substance use, and begin to form a solid sense of identity and self-image.
- Multi- or biracial individuals may struggle to find acceptance from other ethnic or racial groups, as their mixed identity can be met with disdain, confusion, or rejection from others.
- LGBTQ+ individuals may commonly face intense discrimination at work and in public, and are at increased risk of intimate partner violence, which may contribute to the development of a depressive disorder.
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How can you reduce your risk of depression?
Just as there’s no single cause of depression, reducing your risk requires multiple strategies. Here are some evidence-backed ways to protect your mental health:
1. Build real connections beyond social media.
Make time for in-person relationships with people who genuinely support you. Call a friend instead of scrolling their feed. Meet for coffee instead of texting.
Having meaningful, supportive relationships serves as an effective buffer against the pain of isolation and loneliness that are often byproducts of depressive disorders. As your relationships grow stronger and more interconnected, the sense of purpose and mastery that positive interactions lend you can serve as a barrier to the isolating and damaging effects of depression.
We may connect with our friends virtually through social media, but evidence suggests that when we’re on the cusp of becoming depressed or are looking for a deeper sense of social connection, our favorite apps aren’t likely to be fulfilling.
2. Focus on sleep quality, not just quantity.
Getting seven to nine hours isn’t enough if your sleep is fragmented or restless. Create a consistent bedtime routine, keep your bedroom cool and dark, and avoid screens an hour before bed. Research shows that good sleep hygiene practices and getting enough sleep can be a protective factor against developing or worsening depression.
3. Move your body most days of the week.
Aim for 30 minutes of movement—walking, dancing, lifting weights, whatever you’ll actually do—three to five days per week. Exercise promotes dopamine and serotonin production, and although neither chemical (in the case of a deficiency) is solely responsible for depressive symptoms, stable levels of feel-good chemicals in the brain likely play a supporting role in preventing depression.
4. Eat foods that support your brain and gut.
Try adding more salmon, avocados, nuts, fermented foods like kimchi and yogurt, and leafy greens into your diet. A healthy gut microbiome is linked to better mental health, and the omega-3 fatty acids can help regulate mood and improve cognitive function.
5. Work with a mental health provider.
Therapists and psychiatric providers can help you identify your specific risk factors and develop personalized strategies to manage symptoms. While friends and family matter, professional support gives you evidence-based tools that social support alone can’t provide. Early treatment can significantly reduce both the severity and duration of depression.
The bottom line
Depression develops from multiple factors working together, which is why reducing your risk requires a multilayered approach.
“The best practices involve a toolbox of strategies rather than a single cure-all,” Dumler says. “Establish a consistent exercise routine, emphasize whole foods, identify a support network, get outside, incorporate laughter, and develop healthy coping outlets.”
McSparran echoes this focus on basics, adding: “Get enough sleep, take your meds, spend time with people you enjoy, do something creative. None of these will fix or prevent depression on their own, but they can all be part of our armor against life’s stressors.”
Understanding which factors contribute to your depression—whether biological, psychological, medical, or environmental—helps you and your provider treat it at the root. The more you understand what’s driving your symptoms, the more effectively you can address them.
