What Is Depression?

Depression — also known as major depressive disorder (MDD) or clinical depression — affects not only your mood, but also your ability to feel, think, and function. It blunts sensations of pleasure, closes off connectedness, stifles creativity, and, at its worst, shuts down hope. It also often causes deep emotional pain not only to the person experiencing it but to that person’s close family and friends.
What Are the Different Types of Depression?
In addition to MDD, there are several other kinds of depression, including:
- Persistent depressive disorder (PDD), previously known as dysthymia, is diagnosed in people who experience persistent mild to moderate depression for at least two years at a time.
- Bipolar disorder, formerly called manic depression, is characterized by moods that cycle between extreme highs (mania) and lows (depression), often with periods of neutral mood in between. Bipolar disorder affects 2.8 percent of U.S. adults.
- Seasonal affective disorder (SAD) is depression that occurs at the same time each year, usually beginning in fall and persisting through winter. SAD is associated with changes in daylight hours, and is often accompanied by increased sleep, weight gain, and cravings for foods high in carbohydrates.
- Premenstrual dysphoric disorder (PMDD) is a more serious form of premenstrual syndrome (PMS). PMDD usually develops a week or two before a woman’s period.
- Postpartum (or perinatal) depression (PPD) is diagnosed in women who experience symptoms of major depression shortly after giving birth (or during pregnancy). PPD is usually related to a combination of factors, including sharp changes in hormone levels following childbirth. Feelings of intense sadness, anxiety, or exhaustion are much stronger, and last longer, than the “baby blues” — the relatively mild symptoms of depression and anxiety that many new mothers experience in the first few days after childbirth.
Signs and Symptoms of Depression
- Depressed mood
- Loss of interest or pleasure in your work, hobbies, friends, family, and other things you once enjoyed
- Tearfulness, emptiness, worthlessness, or guilt
- Hopelessness
- Dramatic changes in your appetite or your weight not related to dieting
- Feelings of listlessness or fatigue for no obvious reason
- Trouble concentrating or making decisions
- Anxious restlessness that manifests in ways like pacing or wringing your hands — or the opposite — moving or speaking more slowly than usual
- Insomnia or sleeping too much
- Recurrent thoughts of suicide or death
- Planning or attempting suicide
Unusual Symptoms of Depression
Causes and Risk Factors of Depression
No one knows for sure why some people become depressed and others do not. Depression can occur spontaneously, without any obvious cause. And it’s well documented that once you’ve had one depressive episode, your risk of having another later in life increases.
Among the potential contributors to depression are:
- Genetics Many studies suggest that depression can spring from a genetic predisposition, including one international study involving more than 807,000 people, that linked 269 genes to depression. Scientists think that while some genes may increase risk, other factors are needed to trigger symptoms.
- Neurotransmitters The long-held idea that depression is caused by low levels of the neurotransmitter serotonin (a chemical messenger that communicates between neurons) has been debunked, according to one review. But it’s clear that neurotransmitters play a role, at least for some people. Experts’ current belief is that the relationship between depression and neurotransmitters is complex and may be related to nerve cell connections, nerve cell growth, or the functioning of nerve circuits.
- Inflammation Research indicates that disease-related or stress-related inflammation may create chemical changes in the brain that can trigger or worsen depression in certain people and influence how a person responds to drug therapy.
- Hardship There’s evidence that psychological and social factors like a history of abuse, poor health and nutrition, unemployment, social isolation or loneliness, low socioeconomic status, or stressful life events (divorce or money worries, for example) can play a decisive role in the onset of depression.
- Traumatic Brain Injury (TBI) Another all-too-common cause of depression is TBIs. In 2021, more than 214,000 people were hospitalized for TBIs, such as a concussion, following a bump or blow to the head from things like falls, assaults, car accidents, and workplace and sports-related injuries. One study found that people who’d experienced a TBI were 11 times more likely to meet the criteria for depression one year after the injury.
How Is Depression Diagnosed?
It may also be helpful to take an online, clinically validated depression test known as the PHQ-9 patient health questionnaire. This test is short and straightforward, and it may help you get a better idea of whether you may be experiencing depression.
Treatment and Medication Options for Depression
Talk Therapy for Depression
- Behavioral Activation Therapy The aim of this type of therapy is to reverse the downward spiral of depression by encouraging you to seek out experiences and activities that give you joy.
- Cognitive Behavioral Therapy (CBT) CBT focuses on changing specific negative thought patterns so that you can better respond to challenging and stressful situations.
- Interpersonal Therapy This very structured, time-limited form of therapy focuses on identifying and improving problematic personal relationships and circumstances directly related to your current depressive mood.
- Problem-Solving Therapy This therapy is a form of CBT that teaches take-charge skills that help you solve real-life problems and stressors, big and small, that contribute to depression.
- Self-Management or Self-Control Therapy This type of behavioral therapy trains you to lessen your negative reactions to events and reduce your self-punishing behaviors and thoughts.
Medication for Depression
- Selective Serotonin Reuptake Inhibitors (SSRIs) This category of drug includes fluoxetine (Prozac), citalopram (Celexa), and sertraline (Zoloft) and targets serotonin, a neurotransmitter that helps control mood, appetite, and sleep.
- Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs) SNRIs include drugs like duloxetine (Cymbalta), desvenlafaxine (Pristiq), and venlafaxine (Effexor XR), which block the reabsorption of both serotonin and another neurotransmitter, norepinephrine.
- Norepinephrine-Dopamine Reuptake Inhibitors (NDRIs) This class of medications includes bupropion.
- Tricyclic or Tetracyclic Antidepressants (TCAs) TCAs include such drugs as imipramine (Tofranil) and nortriptyline (Pamelor). These drugs were among the earliest antidepressants to come on the market. These days, doctors generally only turn to them when treatment with SSRIs, SNRIs, and NDRIs has failed.
- Monoamine Oxidase Inhibitors (MAOIs) MAOIs, including phenelzine (Nardil) and isocarboxazid (Marplan), were the first antidepressants developed. They’re rarely used today, in part because people who take them require careful monitoring to prevent negative interactions with certain foods and other medications.
- N-Methyl D-Aspartate (NMDA) Receptor Antagonists NDMAs help maintain the balance of glutamate and gamma-aminobutyric acid (GABA) in the body. They can help people whose symptoms haven’t been relieved by standard treatments and often work more rapidly than other antidepressants. They include drugs like esketamine (Spravato) and dextromethorphan-bupropion (Auvelity).
- Neuroactive Steroids Neuroactive steroids are believed to work by affecting GABA levels. They often work more rapidly than other antidepressants. They include drugs like brexanolone (Zulresso) and zuranolone (Zurzuvae), which are both FDA-approved to treat postpartum depression.
- Serotonin Receptor Agonists This new class of antidepressants is thought to work by affecting certain serotonin receptors in the brain that help regulate mood and emotions. This class includes the drug gepirone ER (Exxua).
- Nausea
- Headache
- Drowsiness
- Diarrhea
- Upset stomach
- Dry mouth
- Weight gain
- Sexual problems
In addition, it may take some patience before you see results. The full benefits of the drugs may not be realized until you’ve taken them for as long as three months.
Sometimes, other medications may be added to your regimen, depending on the form of depression, the severity of your symptoms, and your response to other therapies. These might include a mood stabilizer, such as lithium (sold under several brand names) or valproic acid (Depakene, Depakote).
If your depression isn’t improving enough with standard treatments, or if symptoms of psychosis (having delusions or seeing or hearing voices that are not real, for example) are present, a doctor may prescribe an antipsychotic medication.
Should You Worry About Antidepressant Withdrawal?
What Is Treatment Resistant Depression and Is There Any Help for It?
It is not, however, a hopeless condition. A number of treatment approaches for TRD are available, including:
- Esketamine (Spravato) A nasal spray, Spravato won FDA approval on March 5, 2019, as a new treatment for TRD. It is derived from ketamine, a veterinary anesthetic best known as the street drug “Special K.” Because of safety concerns, Spravato must be administered in a medical office and can be taken on its own or in combination with an oral antidepressant.
- Electroconvulsive Therapy (ECT) ECT involves a brief electrical stimulation of the brain while the patient is under anesthesia. ECT rapidly provides substantial improvement in approximately 80 percent of patients with severe, uncomplicated major depression. Like any medical procedure, ECT is associated with side effects — most commonly, issues with memory. In most cases, this is short-term; however, some people can experience permanent gaps in memory.
- Transcranial Magnetic Stimulation (TMS) TMS uses rapidly alternating magnetic fields to change activity in specific areas of the brain. Although researchers don’t fully understand how exactly TMS affects the brain, it appears to influence how the brain is operating and, in turn, improve mood and decrease depressive symptoms.
- Vagus Nerve Stimulation This therapy involves implanting a tiny device in the chest that provides regular mild electrical pulses to the longest of the nerves that arise from the brain. Vagus nerve stimulation has been found to significantly improve quality of life for many patients.
- Psychedelic Drugs While not yet FDA approved, microdosing with psychedelic drugs to produce a more positive mood in people with chronic depression is the focus of a flurry of research worldwide. Evidence has yet to endorse the use of psychedelics for the treatment of any mental health condition except during approved investigational studies, and more research is needed in this field.
Have You Ever Experienced Antidepressant Withdrawal?
Prevention of Depression
- If you suspect you have depression, get professional help early on to keep it from getting worse.
- Lean on your family or friends for support.
- Consider long-term treatment to prevent your depressive symptoms from coming back even after you feel better
- Try your best to curb stress in your life.
Lifestyle Changes for Depression
Diet changes, too, can uplift your mood by reducing inflammation and helping to ensure your brain gets the nutrients it needs to function at its best.
How Long Does Depression Last?
Complications of Depression
- Misuse of alcohol or drugs
- Anxiety disorders
- Social isolation
- Family or relationship difficulties
- Work or school issues
- Excess weight, which can lead to diabetes or heart disease
- Pain
- Self-harm or suicide
- Early death from other medical conditions
Research and Statistics: How Many People Have Depression?
Disparities and Inequities in Depression
Research suggests that the following disparities and inequities exist when it comes to depression.
Gender and Depression
People of Color and Depression
Research on depression within communities of color has revealed a number of differences in the symptoms, diagnosis, and treatment between people of color and white communities.
The symptoms of depression may appear different among people of color than in white people. For instance, while white people are more likely to have acute depressive episodes, African Americans are more likely to experience depression that’s chronic, prolonged, and debilitating.
Importantly, the authors of the study noted, traditional depression screening tools may not capture these symptoms, meaning depression may go undetected in some Black and African American women.
Related Conditions for Depression
- Anxiety disorders
- Bipolar disorder
- Eating disorders
- Grief or bereavement
- Schizoaffective disorder
- Schizophrenia
- Substance- or medication-induced depressive disorder
The Takeaway
- Depression is a complex mental health condition that can significantly affect your mood and the way you think, feel, act, and function.
- The causes of depression are not fully understood, but research suggests factors like genetics, environment, emotional trauma and hardships, traumatic brain injury, and inflammation may play a role.
- Treatment usually centers on talk therapy and antidepressant medications. Lifestyle changes can also help.
If you or a loved one is experiencing significant distress or having thoughts about suicide and need support, call or text 988 to reach the 988 Suicide & Crisis Lifeline, available 24/7. If you need immediate help, call 911.
Common Questions & Answers
Resources We Trust
- Mayo Clinic: Depression (Major Depressive Disorder)
- Cleveland Clinic: Depression
- Families for Depression Awareness: Help Prevent Suicides
- Depression and Bipolar Support Alliance: Depression
- Anxiety & Depression Association of America: What Is Depression?
- Persistent Depressive Disorder: Symptoms and Treatment. Cleveland Clinic. September 28, 2024.
- Bipolar Disorder. National Institute of Mental Health.
- Seasonal Affective Disorder (SAD). Mayo Clinic.
- Premenstrual dysphoric disorder (PMDD). Office on Women’s Health.
- Postpartum Depression. American College of Obstetricians and Gynecologists.
- What Is Depression? American Psychiatric Association. April 2024.
- Liu Q et al. Aggressive outbursts among adults with major depressive disorder: Results from the Collaborative Psychiatric Epidemiological Surveys. Journal of Psychiatric Research. March 2021.
- Depression (major depressive disorder): Symptoms & causes. Mayo Clinic. October 14, 2022.
- Hopwood M. Anxiety Symptoms in Patients with Major Depressive Disorder: Commentary on Prevalence and Clinical Implications. Neurology and Therapy. April 28, 2023.
- Hall-Flavin DK. Depression can cause pain — and pain can cause depression. Mayo Clinic. April 3, 2019.
- Pies RW. Debunking the Two Chemical Imbalance Myths, Again. Psychiatric Times. August 2, 2019.
- Howard DM et al. Genome-wide meta-analysis of depression identifies 102 independent variants and highlights the importance of the prefrontal brain regions. Nature Neuroscience. March 2019.
- Moncrieff J et al. The serotonin theory of depression: a systematic umbrella review of the evidence. Molecular Psychiatry. August 2023.
- What causes depression? Harvard Health Publishing. January 10, 2022.
- Beurel E et al. The Bidirectional Relationship of Depression and Inflammation: Double Trouble. Neuron. July 22, 2020.
- Social Determinants of Mental Health. World Health Organization.
- Traumatic Brain Injury and Concussion. Centers for Disease Control and Prevention. October 29, 2024.
- Choi Y et al. Incidence of Depression After Traumatic Brain Injury: A Nationwide Longitudinal Study of 2.2 Million Adults. Journal of Neurotrauma. February 22, 2022.
- Depression. National Institute of Mental Health. 2024.
- Depression and Suicide Risk: Screening. U.S. Preventive Services Task Force. June 20, 2023.
- Salcedo B. Depression Treatment – It Works. Anxiety and Depression Association of America. October 2020.
- Treatment Target: Depression. Society of Clinical Psychology.
- Antidepressants: Selecting one that’s right for you. Mayo Clinic. September 23, 2022.
- Antidepressants. Cleveland Clinic. March 1, 2023.
- Maguire JL et al. Neurosteroids: mechanistic considerations and clinical prospects. Neuropsychopharmacology. January 2024.
- A New Dawn: FDA Greenlights Exxua (Gepirone ER) for Major Depressive Disorder. McGovern Medical School. January 29, 2024.
- Jha MK et al. Pharmacotherapies for Treatment-Resistant Depression: How Antipsychotics Fit in the Rapidly Evolving Therapeutic Landscape. American Journal of Psychiatry. March 2023.
- Antidepressant Discontinuation Syndrome. Cleveland Clinic.
- Henssler J et al. Incidence of antidepressant discontinuation symptoms: A systematic review and meta-analysis. Lancet Psychiatry. July 2024.
- Peter J et al. Managing Suicidal Thoughts, Behaviors, and Risk in Treatment-Resistant Depression. Psychiatric Times. April 9, 2024.
- FDA approves new nasal spray medication for treatment-resistant depression; available only at a certified doctor’s office or clinic. U.S. Food and Drug Administration. March 5, 2019.
- SPRAVATO (esketamine) approved in the U.S. as the first and only monotherapy for adults with treatment-resistant depression. Johnson & Johnson. 2025.
- What Is Electroconvulsive Therapy (ECT)? American Psychiatric Association. January 2023.
- Transcranial Magnetic Stimulation. Mayo Clinic. April 7, 2023.
- Austelle CW et al. A Comprehensive Review of Vagus Nerve Stimulation for Depression. Neuromodulation. September 6, 2021.
- Position Statement on the Use of Psychedelic and Empathogenic Agents for Mental Illnesses. American Psychiatric Association. July 2022.
- Depression (major depressive disorder): Diagnosis & treatment. Mayo Clinic. October 14, 2022.
- Francis HM et al. A brief diet intervention can reduce symptoms of depression in young adults — a randomised controlled trial. PLoS One. October 9, 2019.
- Bains N et al. Major Depressive Disorder. StatPearls. April 10, 2023.
- Depression (Major Depressive Disorder). Mayo Clinic. October 14, 2022.
- Major Depression. National Institute of Mental Health. July 2023.
- Bailey RK et al. Racial and ethnic differences in depression: current perspectives. Neuropsychiatric Disease and Treatment. February 22, 2019.
- Women and Depression. Anxiety and Depression Association of America.
- Depression During Pregnancy. American College of Obstetricians and Gynecologists.
- Perez NB. Latent Class Analysis of Depressive Symptom Phenotypes Among Black/African American Mothers. Nursing Research. 2023.
- Mental Health Challenges and Support: Latinx Communities. National Alliance on Mental Illness (NAMI) California.
- Why Asian-Americans and Pacific Islanders Don’t Go to Therapy. National Alliance on Mental Illness. July 25, 2019.

Angela D. Harper, MD
Medical Reviewer
Angela D. Harper, MD, is in private practice at Columbia Psychiatric Associates in South Carolina, where she provides evaluations, medication management, and psychotherapy for adults.
A distinguished fellow of the American Psychiatric Association, Dr. Harper has worked as a psychiatrist throughout her career, serving a large number of patients in various settings, including a psychiatric hospital on the inpatient psychiatric and addiction units, a community mental health center, and a 350-bed nursing home and rehab facility. She has provided legal case consultation for a number of attorneys.
Harper graduated magna cum laude from Furman University with a bachelor's degree and cum laude from the University of South Carolina School of Medicine, where she also completed her residency in adult psychiatry. During residency, she won numerous awards, including the Laughlin Fellowship from the American College of Psychiatrists, the Ginsberg Fellowship from the American Association of Directors of Psychiatric Residency Training, and resident of the year and resident medical student teacher of the year. She was also the member-in-training trustee to the American Psychiatric Association board of trustees during her last two years of residency training.
Harper volunteered for a five-year term on her medical school's admission committee, has given numerous presentations, and has taught medical students and residents. She currently supervises a nurse practitioner. She is passionate about volunteering for the state medical board's medical disciplinary commission, on which she has served since 2015.
She and her husband are avid travelers and have been to over 55 countries and territories.

Nuna Alberts, LCSW
Author
Nuna Alberts, LCSW, has been in private practice for more than 20 years, treating hundreds of adolescents, adults, and couples for depression, anxiety, obsessive compulsive disorder, relationship problems and a range of other issues.
She earned a bachelor's in art history from Columbia University School of General Studies, with an emphasis on criticism, and received a master's in social work from New York University, where she focused on psychodynamic psychotherapy. For her master's in journalism thesis for Columbia University, she wrote about genetic testing and the ethical choices that can arise from it.
Her writing has been published in multiple magazines and national newspapers, and she was the editor and an author of the 2002 book Strengthen Your Immune System: Boosting the Body's Own Healing Powers in the Fight Against Disease. She is currently working on a book about psychotherapists' perspectives on their own psychotherapy.