Depression: symptoms, causes, diagnosis, and treatment

Tzvi Doron, DO - Contributor Avatar

Reviewed by Tzvi Doron, DO and 

Tzvi Doron, DO - Contributor Avatar

Reviewed by Tzvi Doron, DO and 

LAST UPDATED: May 25, 2021


Depression not only robs people of years of their lives but also severely decreases their quality of life. Many people will experience at least one depressive episode at some point in their lives. Depression is still one of the most overlooked causes of death and suffering in the U.S. 

It’s important to understand the far-reaching negative impacts of depression. Even if you’re not struggling with this illness, chances are, someone you know is grappling with this silent killer. They just haven’t told you about it.


Improve and support your health from the comfort of home

What is depression?

Most people would describe depression as feelings of sadness or loss. But it is more than just feeling “down.” Depression is a mental health condition that affects many Americans. In 2019, the Centers for Disease Control and Prevention (CDC) reported that 18.5% of adults had symptoms of depression in the previous two weeks (Villarroel, 2019).

The harmful effects of depression extend to all facets of people’s lives, including their personal life and work environments. Depression is even a major cause of lost work productivity due to chronic absenteeism and even “presenteeism.” Presenteeism is when you’re technically at your desk, but you’re either too sick or too out of it to get much done (Rost, 2014). 

It’s important to note the distinction between feeling sad and clinical depression. People with depression aren’t just having a bad day or even a tough week. When you’re going through a depressive episode, it changes everything about your life. Depression disrupts your sleep patterns, diet, social interactions, energy levels, motivation, and thoughts of self-worth. 

Depression isn’t something you can “power through”—nor should you. It’s important to reach out and get help, so a depressive episode doesn’t spiral out of control. It’s also essential to recognize signs or symptoms of depression in your friends and family because people who are depressed often don’t reach out for help. Nearly 60% of people with depression do not seek medical help—and the consequences can be deadly (Chand, 2020-a).

Signs and symptoms of depression

The Fifth Edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM 5) defines major depressive disorder (MDD) as “two or more weeks of 5 of the following symptoms that cause problems with social, occupational, or other areas of functioning” (at least one of the first two is necessary) (Chand, 2020-a):

  • Depressed mood

  • Decreased interest or pleasure in doing things

  • Weight loss or weight gain, or increased or decreased appetite

  • Insomnia or sleeping too much

  • Moving slowly, or being fidgety or restless

  • Fatigue or loss of energy

  • Feelings of excessive guilt, worthlessness, or low self-esteem

  • Difficulty concentrating or making decisions

  • Recurrent thoughts of death or suicide

If you have experienced any of these symptoms, know that you are not alone—in a 2019 study, the CDC found that nearly 20% of American adults experienced some symptoms of depression within the previous two weeks (Villarroel, 2019).

It’s important to note that having one or two symptoms of depression is normal. Don’t panic if you recognize some of these criteria in your own life. It’s even normal to have several symptoms for a day or two. That doesn’t make you depressed. It makes you a human being. You’re allowed to experience a full range of emotions—even the bad ones.

It’s also common for people to go through similar feelings after a major loss, such as losing a loved one or losing your job. These don’t qualify as depression either—unless those feelings last for longer than the expected amount of time. Other types of depression differ by the cause and the degree/duration of symptoms.

Types of depression

Depression is a mood disorder that can be divided into different types, including (NIMH, 2018): 

  • Major depressive disorder (MDD)

  • Persistent depressive disorder (dysthymia)

  • Postpartum depression

  • Seasonal affective disorder

  • Psychotic depression

Major depressive disorder (MDD) 

Major depressive disorder is the one that most people think of when they talk about depression. As mentioned above, MDD is a clinical diagnosis that requires five or more symptoms to be present for two weeks or longer. 

Persistent depressive disorder

Persistent depressive disorder (also called dysthymia) is a depressed mood that lasts for at least two years —it used to be called chronic depression. This is not a well-understood form of depression and has only been recently recognized as a mood disorder rather than a personality disorder. Approximately 3% of American adults have persistent depressive disorder. You can have persistent depressive disorder and major depression, but the symptoms have to last for at least two years to be considered persistent depressive disorder (Patel 2020).

Postpartum depression

Postpartum depression (PPD) is often confused with the “baby blues,” but it is a more serious condition. Baby blues are mild depression and/or anxiety symptoms that usually resolve within a few weeks after giving birth—many women experience these feelings. Still, they go away on their own (Mughal, 2020). 

Postpartum depression is a type of major depression that doesn’t improve after delivery. The feelings of anxiety, sadness, loss of interest and energy, and suicidal thoughts in some cases may make getting through the day and taking care of themselves and their babies difficult. Around one in seven women develop postpartum depression, and as many as half don’t tell their families about their struggles (Mughal, 2020).  

Seasonal affective disorder

Many people feel down, gloomy, or lethargic during the darker days of winter—some call this feeling the “winter blues.” However, if these depressed feelings start to affect your ability to do normal activities, like sleep and social interactions, you may have seasonal affective disorder (SAD). Seasonal affective disorder is an episodic depression that affects people when there is less natural sunlight, i.e., during the winter months. Your mood improves in the spring and summer, and treatment often involves light therapy, in addition to other options (Munir, 2021).  

Psychotic depression

If someone has a form of psychosis plus depression, it is considered psychotic depression. Psychotic episodes usually involve seeing or hearing something that is not there (hallucinations) or having fixed false beliefs (delusions). People with psychotic depression usually have depressive symptoms, like feelings of worthlessness or guilt, along with their psychosis (Rothschild, 2020).

Risk factors for depression

Several genetic and environmental factors seem to increase the likelihood that you develop depression, including (Chand, 2020-a):

  • A family history of a first-degree relative (a parent, sibling, or child) with depression 

  • Certain medical conditions, like Alzheimer’s disease, Parkinson’s disease, stroke, multiple sclerosis, thyroid disease, and chronic pain 

  • Traumatic life events or history of trauma

  • Drug abuse

Triggers for depression

As mentioned earlier, it is expected that people will go through some of the symptoms of depression after a major loss or traumatic life event. However, depression becomes a medical condition when these feelings last too long or prevent you from functioning. 

Triggers for the development of depression include a lack or loss of social support, caregiver burden, personal conflicts, financial or employment problems, among others. 

Health risks of depression

While suicide is the worst result of depression, depressive episodes can harm you in several other ways. For example, insomnia alone contributes to all types of health risks, like diabetes, hormone imbalance, and hypertension (which can lead to heart attacks and stroke). Clinical depression is a risk factor for many illnesses and even all-cause mortality (death from any cause).

Depression and heart disease, diabetes, and stroke

Depression can increase your risk of high blood pressure, heart disease, and heart attacks—this includes an increased risk of fatal heart attacks (Charlson, 2013). Even worse, if you’ve already had a heart attack, depression increases the risk of actually dying from the next one (Lichtman, 2014). 

Similarly, depressed people with diabetes face an increased risk of cardiovascular disease and an almost 50% increased risk of dying from all causes (Dooren, 2013). Depression is also associated with a higher risk of stroke and death from stroke and a higher risk of heart failure (Pan, 2011; Freedland, 2011). 

It’s important to note that while depression is associated with higher risks for heart disease, stroke, and heart failure, we don’t know if it’s a risk factor or simply a risk marker (it’s associated with the diseases, but it’s not the cause). Either way, depressive episodes are bad for your health, especially if you’re at risk for stroke, heart disease, or diabetes.

Depression and cancer

There may be a small increased risk of cancer in people with depression, but more studies are needed to support this association (Jia, 2017). Depression may also increase the risk of dying in those who already have cancer (Wang, 2020). 

Again, it’s not clear whether depression itself is the cause of this increased mortality or simply a marker for it. For example, it’s completely plausible that people struggling with cancer are more likely to be depressed—especially as their illness progresses.

Depression and dementia

The part of the brain associated with memory shrinks in people with depression. Both early- and late-life depression are associated with an increased risk of various types of dementia, including the most common type of dementia—Alzheimer’s disease (da Silva, 2013). 

However, it’s not clear why people with depression have higher rates of dementia. Some theories include the toxic effects of cortisol on parts of the brain, like the hippocampus. The hippocampus is involved with memory and actually gets smaller in people with depression. At the same time, inflammation in different parts of the brain and a decrease in neurotrophins (chemicals that keep the brain healthy) are other likely culprits for this loss of brain function (Rakesh, 2017).

Depression and mortality

While heart disease is the leading cause of death in the United States, depression is responsible for damaging thousands of lives and ending many of those lives prematurely. Clinical depression is a silent killer, and it’s reaching epidemic levels in the U.S.

The most direct way that depression kills is suicide. Suicide is the tenth most common cause of death in the U.S. and the second most common cause of death in 15 to 34-year-olds. That’s more than twice the number of homicides. In addition, while women are more likely to attempt suicide than men, men are almost four times as likely to die of suicide. And suicide rates have been climbing over the last two decades (NIMH, 2021). Depression is the number one cause of suicide (Olfson, 2016).

But it’s not just suicide affecting mortality. An extensive Journal of American Medicine analysis of over 2,000 studies showed that depression (and other mental disorders) increases your risk of mortality from any cause—in other words, people with depression don’t live as long, on average. In fact, the study found that depression shortened life expectancy across the board by ten years (Walker, 2015). 

Treatments for depression

Although we don’t know for sure whether depression itself is the cause of increased mortality in all of these patient populations, we know it’s an important risk factor. Thankfully, there are effective treatments available to decrease the suffering caused by this disease and perhaps lower the risks of depression’s interaction with the other diseases discussed.

Rule out medical causes

If you or a loved one have depression, see a healthcare provider. Your health professional can rule out medical causes of depression like hypothyroidism, vitamin B12 deficiency, low testosterone, and other complications and side effects of medications. If a potential medical cause is found, it’s important to treat the cause before starting depression-specific treatment.

Unfortunately, depression isn’t often caused by the straightforward medical issues listed above. If your depression doesn’t have a diagnosable medical cause, the two mainstays for treating depression are medication and psychotherapy.

Antidepressant medications

The most common antidepressant medications are selective serotonin reuptake inhibitors (SSRIs), which include drugs like fluoxetine (brand name Prozac; see Important Safety Information), sertraline (brand name Zoloft; see Important Safety Information), and escitalopram (brand name Lexapro; see Important Safety Information), to name a few. Serotonin-norepinephrine reuptake inhibitors (SNRIs) are also popular, including drugs like venlafaxine (brand name Effexor; see Important Safety Information), duloxetine (brand name Cymbalta; see Important Safety Information), and desvenlafaxine (brand name Pristiq) (Rush, 2020). 

Talk to your healthcare provider about potential interactions and side effects before beginning treatment with these drugs. Not everyone reacts favorably to each prescription, so work with your healthcare provider to find the right medication for you.


Psychotherapy is another important part of managing depression. Research shows that antidepressants and cognitive behavioral therapy (CBT) are equally effective, but you may achieve long-term benefits from CBT (Boschloo, 2019; Rush, 2020). However, using CBT and medication together may be better than either treatment alone (Chand, 2020-b). CBT treats depression by encouraging people to replace harmful thoughts with more positive ones. 

CBT is the most well-researched form of psychotherapy for depression. What’s more, there’s a growing body of research around the potential of mindfulness-based cognitive therapy (MBCT) for treating depression. MBCT and CBT are akin to meditation therapy. They combine mindfulness practices aimed at experiencing the present moment with breathing exercises and awareness (Hofmann, 2017).

Treating depression with diet and exercise

What’s good for your physical health is also good for your mental health. So it should come as no surprise that increased physical activity can help relieve depression (Schuch, 2019). 

Similarly, a healthy diet may also decrease the health risks of depression. In some studies, researchers have found that the Mediterranean diet (olive oil, “good” fatty foods, nuts, fruits, and legumes) is associated with a lower rate of depression (Parletta, 2019). 

Other factors that may impact the risk for depression include poor sleep, lack of social interaction, and excessive use of alcohol and tobacco. But it’s worth noting that a healthy diet and regular exercise can have a positive effect on depression.

Treatment-resistant depression

One challenge of depression is that it’s a moving target and highly personalized. Unfortunately, some people don’t respond to multiple treatments for their depression, a condition called treatment-resistant depression (Akil, 2018). If you have other mental health issues, like anxiety disorders, bipolar disorder, substance use, etc., you may be at higher risk for having treatment-resistant depression. But that doesn’t mean you should give up after the first failed attempt (Thase, 2020). 

Many people respond to variations in treatment and even a combination of medication, therapy, and lifestyle changes. There are even several non-conventional treatments available for people who don’t respond to the more standard options (Thase, 2020).

Electroconvulsive therapy

Probably the oldest alternative treatment method for depression is electroconvulsive therapy (ECT) (Salik, 2020). Unfortunately, most people have only seen ECT in the context of old horror films, but it’s an effective and safe treatment.

ECT works by placing electrodes on specific parts of the scalp and applying enough current to produce a seizure that affects neurons and chemicals in the brain. It sounds grizzly, but the procedure is done under general anesthesia (people are asleep during the procedure) and has been upgraded significantly since it first came into practice in the 1930s. ECT is more effective than medication and is generally safe, but its main undesirable side effect is short-term memory loss (Salik, 2020).

A leading theory for how ECT works is that it increases the growth of neurons and the connections between neurons through increasing levels of brain-derived neurotrophic factor (BDNF). People who receive ECT can still struggle with depression. However, electroconvulsive therapy is very effective at abruptly stopping an episode of depression and may be very useful in severely depressed and acutely suicidal people. Most people undergo 4–6 treatments before they see major improvement (Salik, 2020).

Repetitive transcranial magnetic stimulation

Although ECT is very effective, it does have a few downsides, including the need for general anesthesia and short-term memory loss. These shortcomings, along with the public opinion of ECT, have led to developing other ways to stimulate the brain to produce an antidepressant effect. The most popular method of alternative brain stimulation is repetitive transcranial magnetic stimulation (rTMS) (Downar, 2016).

This treatment uses magnets to stimulate certain areas of the brain instead of an electric current. The method is different from ECT, but the goal is the same—neural growth and connection. rTMS has been found to be somewhat effective for treatment-resistant depression, but it’s still not as effective as ECT (Micallef-Trigona, 2014). Therefore, for acutely suicidal hospitalized patients, ECT is usually the route that is taken when medication isn’t effective, or patients want faster results.

Ketamine treatment

Ketamine is another really interesting option for treatment-resistant depression. Generally used in the hospital for anesthesia, smaller doses of ketamine appear to have rapid antidepressant effects—especially in suicidal patients. 

The downside is that the antidepressant effects of ketamine aren’t permanent. The other problem is that ketamine is a drug that’s often sold illegally and routinely abused. It’s extremely important that you get ketamine treatment for depression from an experienced healthcare provider if you decide to explore this option (Corriger, 2019).

Get the help you need

Depression not only robs people of years of their lives but also severely decreases quality of life. Many people will experience at least one major depressive episode at some point in their lives. However, there are numerous things you can do to decrease your risk of developing clinical depression—like eating a healthy diet, exercising, getting regular checkups, and cultivating active relationships with friends and loved ones.

Many conventional and alternative treatments exist for depression. If you or a loved one are experiencing depression, help is out there. You don’t have to suffer in silence, and depression doesn’t have to end your life early.

Suicide Prevention Lifeline

Anxiety and Depression Association of America: List of Support Groups by Region


If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

  • Akil, H., Gordon, J., Hen, R., Javitch, J., Mayberg, H., McEwen, B., et al. (2018). Treatment resistant depression: a multi-scale, systems biology approach. Neuroscience and Biobehavioral Reviews, 84, 272–288. doi:10.1016/j.neubiorev.2017.08.019. Retrieved from

  • Bains N, Abdijadid S. (2020). Major depressive disorder. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Retrieved from

  • Boschloo, L., Bekhuis, E., Weitz, E. S., Reijnders, M., DeRubeis, R. J., Dimidjian, S., et al. (2019). The symptom-specific efficacy of antidepressant medication vs. cognitive behavioral therapy in the treatment of depression: results from an individual patient data meta-analysis. World Psychiatry:Official Journal of the World Psychiatric Association (WPA), 18(2), 183–191. doi:10.1002/wps.20630. Retrieved from

  • Chand SP, Arif H. (2020-a). Depression. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Retrieved from

  • Chand SP, Kuckel DP, Huecker MR. (2020-b). Cognitive behavior therapy. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Retrieved from

  • Charlson, F. J., Moran, A. E., Freedman, G., Norman, R. E., Stapelberg, N. J., Baxter, A. J., et al. (2013). The contribution of major depression to the global burden of ischemic heart disease: a comparative risk assessment. BMC Medicine, 11(1). doi: 10.1186/1741-7015-11-250. Retrieved from

  • Corriger, A., & Pickering, G. (2019). Ketamine and depression: a narrative review. Drug Design, Development and Therapy, 13, 3051–3067. doi: 10.2147/DDDT.S221437. Retrieved from

  • da Silva, J., Gonçalves-Pereira, M., Xavier, M., & Mukaetova-Ladinska, E. (2013). Affective disorders and risk of developing dementia: Systematic review. British Journal of Psychiatry, 202(3), 177-186. doi: 10.1192/bjp.bp.111.101931. Retrieved from

  • Dooren, F. E. P. V., Nefs, G., Schram, M. T., Verhey, F. R. J., Denollet, J., & Pouwer, F. (2013). Depression and risk of mortality in people with diabetes mellitus: a systematic review and meta-analysis. PLoS ONE, 8(3). doi: 10.1371/journal.pone.0057058. Retrieved from

  • Downar, J., Blumberger, D. M., & Daskalakis, Z. J. (2016). Repetitive transcranial magnetic stimulation: an emerging treatment for medication-resistant depression. Canadian Medical Association Journal, 188(16), 1175–1177. doi: 10.1503/cmaj.151316. Retrieved from

  • Freedland, K. E., Carney, R. M., & Rich, M. W. (2011). Effect of depression on prognosis in heart failure. Heart Failure Clinics, 7(1), 11–21. doi: 10.1016/j.hfc.2010.08.003. Retrieved from

  • Hofmann, Stefan G, and Angelina F Gómez. (2017). Mindfulness-based interventions for anxiety and depression. The Psychiatric Clinics of North America, vol. 40,4: 739-749. doi: 10.1016/j.psc.2017.08.008. Retrieved from

  • Jia, Y., Li, F., Liu, Y. F., Zhao, J. P., Leng, M. M., & Chen, L. (2017). Depression and cancer risk: a systematic review and meta-analysis. Public Health, 149, 138–148. doi: 10.1016/j.puhe.2017.04.026. Retrieved from

  • Lichtman, J. H., Froelicher, E. S., Blumenthal, J. A., Carney, R. M., Doering, L. V., Frasure-Smith, N., et al. (2014). Depression as a risk factor for poor prognosis among patients with acute coronary syndrome: systematic review and recommendations. Circulation, 129(12), 1350–1369. doi: 10.1161/cir.0000000000000019. Retrieved from

  • Micallef-Trigona, B. (2014). Comparing the effects of repetitive transcranial magnetic stimulation and electroconvulsive therapy in the treatment of depression: a systematic review and meta-analysis. Depression Research and Treatment, 2014, 1–8. doi: 10.1155/2014/135049. Retrieved from

  • Mughal S, Azhar Y, Siddiqui W. (2020). Postpartum depression. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Retrieved from

  • Munir S, Abbas M. (2021). Seasonal depressive disorder. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Retrieved from

  • National Institute of Mental Health (NIMH). (2018). Depression. Retrieved on May 18, 2021 from

  • National Institute of Mental Health (NIMH). (2021). Suicide. Retrieved on May 18, 2021 from

  • Olfson, M., Wall, M., Wang, S., Crystal, S., Liu, S.-M., Gerhard, T., et al. (2016). Short-term suicide risk after psychiatric hospital discharge. JAMA Psychiatry, 73(11), 1119. doi: 10.1001/jamapsychiatry.2016.2035. Retrieved from

  • Pan, A., Sun, Q., Okereke, O. I., Rexrode, K. M., & Hu, F. B. (2011). Depression and risk of stroke morbidity and mortality. JAMA, 306(11), 1241. doi: 10.1001/jama.2011.1282. Retrieved from

  • Parletta, N., Zarnowiecki, D., Cho, J., Wilson, A., Bogomolova, S., Villani, A., et al. (2019). A Mediterranean-style dietary intervention supplemented with fish oil improves diet quality and mental health in people with depression: A randomized controlled trial (HELFIMED). Nutritional Neuroscience, 22(7), 474–487. doi:10.1080/1028415X.2017.1411320. Retrieved from

  • Patel RK, Rose GM. (2020). Persistent depressive disorder. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Retrieved from

  • Rakesh, G., Szabo, S. T., Alexopoulos, G. S., & Zannas, A. S. (2017). Strategies for dementia prevention: latest evidence and implications. Therapeutic Advances in Chronic Disease, 8(8-9), 121–136. doi: 10.1177/2040622317712442. Retrieved from

  • Rost, K. M., Meng, H., & Xu, S. (2014). Work productivity loss from depression: evidence from an employer survey. BMC Health Services Research, 14, 597. doi: 10.1186/s12913-014-0597-y. Retrieved from

  • Rothschild, A.J. (2020). Unipolar major depression with psychotic features: Epidemiology, clinical features, assessment, and diagnosis. In UptoDate. Roy-Byrne, P.P. and Solomon, D. (Eds.). Retrieved from

  • Rush, J.A. (2020). Unipolar major depression in adults: choosing initial treatment. In UptoDate. Roy-Byrne, P.P & Solomon, D. (Eds.). Retrieved from

  • Salik I, Marwaha R. (2020). Electroconvulsive therapy. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Retrieved from

  • Schuch, F. B., & Stubbs, B. (2019). The role of exercise in preventing and treating depression. Current Sports Medicine Reports, 18(8), 299–304. doi: 10.1249/JSR.0000000000000620. Retrieved from

  • Thase, M. and Connoly, K.R. (2020). Unipolar treatment resistant depression in adults: epidemiology, risk factors, assessment, and prognosis. In UptoDate. Roy-Byrne, P.P. and Solomon, D. (Eds.). Retrieved from

  • Villarroel MA, Terlizzi EP. (2019) Symptoms of depression among adults: United States. NCHS Data Brief, no 379. Hyattsville, MD: National Center for Health Statistics. 2020. Retrieved from

  • Walker, E. R., McGee, R. E., & Druss, B. G. (2015). Mortality in mental disorders and global disease burden implications: a systematic review and meta-analysis. JAMA psychiatry, 72(4), 334–341. doi: 10.1001/jamapsychiatry.2014.2502. Retrieved from

  • Wang, Y. H., Li, J. Q., Shi, J. F., Que, J. Y., Liu, J. J., Lappin, et al. (2020). Depression and anxiety in relation to cancer incidence and mortality: a systematic review and meta-analysis of cohort studies. Molecular Psychiatry, 25(7), 1487–1499. doi: 10.1038/s41380-019-0595-x. Retrieved from

How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

May 25, 2021

Written by

Tzvi Doron, DO

Fact checked by

Chimene Richa, MD

About the medical reviewers

Dr. Tzvi Doron is Board Certified in Family Medicine by the American Board of Family Medicine.

Dr. Richa is a board-certified Ophthalmologist and medical writer for Ro.