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Major Depressive Disorder: Causes, Symptoms, Treatments,
& More

Depression is a common mental illness that can be debilitating without treatment. Here’s what you need to know about depression.

What is Major Depressive Disorder (MDD)?

Major Depressive Disorder is a mood disorder and serious mental illness. It is characterized by feeling down or depressed most days for at least two weeks, although most episodes last longer. In addition to the mood disturbance, the disorder includes other symptoms that impact how you feel, think, and function. Of particular concern is that depression is associated with suicidal thoughts and behaviors. Although major depression can be debilitating without treatment, the illness is treatable with medications, therapy, or both. With treatment, the disorder is manageable and individuals can live full and productive lives.

What is Major Depressive Disorder?

Over 300 million people in the world are estimated to live with depression, and the disorder is ranked among the leading causes of global disability by the World Health Organization. In the US alone, according to the American Psychiatric Association, an estimated 23 million individuals live with depression in a given year. Prevalence is highest in those 18-29 years old, and the rate is significantly lower in those over 60, although still present. There is consistent evidence that major depressive disorder is more prevalent in women, compared to men. People may only have one depressive episode, but the majority experience more than one episode over their lifetime.

What Causes Major Depressive Disorder?

The exact cause of major depression remains unknown. In most cases, major depression occurs due to a complex combination of factors: including those that are biological, genetic, environmental, and psychological.

Some factors have been identified as contributing to a risk of having major depression during your lifetime, including:

  • History of major depression among first-degree blood relatives
  • Presence of a non-mood disorder (e.g., anxiety, substance use, obsessive-compulsive disorder)
  • History of trauma or adverse childhood experiences
  • Poverty or marginalization
  • Serious medical illnesses
  • Neurotic or negative temperament

What Causes Major Depressive Disorder?
Upsetting and stressful life events can have a role in the onset of major depression in some individuals. Some examples of stressful life events include:

  • Divorce
  • Death of a loved one
  • Loss of employment
  • Factors related to childbirth
  • Financial stress
  • Serious or chronic medical conditions
  • Legal problems

What is the Age of Onset and Course of Major Depressive Disorder?

What is the Age of Onset and Course of Major Depressive Disorder?
Major depression may first appear at any age, but the likelihood of onset rises around puberty. Incidence appears to peak in the 20s and, although rare, there are cases of first onset in the geriatric population.

The course of the disorder is variable across those diagnosed. Some individuals experience discrete episodes, full recovery between episodes, and considerable time between episodes. For others, the time between depressive episodes is shorter and some symptoms linger between episodes. The good news is that 80% of individuals show recovery from a major depressive episode within 12 months and 40% show recovery as soon as 3 months after an episode’s onset.

Additionally, recurrence of a major depressive episode becomes progressively lower over time. Recurrence risk is higher in those with a history of multiple episodes, in younger individuals, and those whose episodes are considered severe.

A proportion of individuals who initially have a depressive episode, will show, in time, to actually have bipolar disorder, cycling between depressive and manic episodes. This is more likely to be the case in those individuals who have onset during adolescence, who have psychotic features as part of their illness, or who have a blood relative with bipolar disorder.

What are the Signs and Symptoms of Major Depressive Disorder?

The signs and symptoms of depression include both mood changes as well as changes in other areas. There are also criteria around how long the symptoms last.

What is Major Depressive Disorder?

The constellation of symptoms that may be observed over a two-week period of a major depressive episode include:

  • Feeling down or depressed, most of the day, nearly every day (in children and adolescents this might be exhibited as irritable mood)
  • Profound loss of interest in things that previously brought pleasure (e.g., hobbies, friendships, activities)
  • Noticeable changes in appetite that lead to considerable weight loss or weight gain
  • Trouble sleeping (insomnia) or, the opposite, sleeping a lot (hypersomnia)
  • Feelings of agitation and restlessness or, the opposite, feeling really slowed down like you are walking through water
  • Decreased energy or feelings of fatigue
  • Feelings of worthlessness or excessive or inappropriate feelings of guilt
  • Trouble concentrating and making decisions
  • Recurrent thoughts of death, recurrent thoughts that you would be better off dead without a plan, attempting suicide or having a specific suicide plan

Individuals experiencing depression likely won’t have every symptom listed above, but rather a combination. The combination of symptoms might not be the same for the same person each time an episode occurs.

Major Depression and Suicide

Major depression is the psychiatric diagnosis most commonly associated with suicide. Not everyone who experiences Major Depression has suicidal thoughts or plans, but it’s important to be aware.
Individuals who are depressed and exhibit the following symptoms could be at particular risk for suicide:

  • Extreme hopelessness
  • A lack of interest in activities that were previously pleasurable
  • Heightened anxiety and/or panic attacks
  • Sleep disturbances
  • Talking about suicide
  • Having a prior history of attempts
  • Irritability and agitation

There are many individual and relational factors that protect someone from suicide risk.

The Lifeline and 988

988 has been designated as the new three-digit dialing code that will route callers to the National Suicide Prevention Lifeline (now known as the 988 Suicide & Crisis Lifeline), and is now active across the United States.

When people call, text, or chat 988, they will be connected to trained counselors that are part of the existing Lifeline network. These trained counselors will listen, understand how their problems are affecting them, provide support, and connect them to resources if necessary.

The previous Lifeline phone number (1-800-273-8255) will always remain available to people in emotional distress or suicidal crisis.

How is Major Depressive Disorder Diagnosed?

How is Major Depressive Disorder Diagnosed?

As with any mental health disorder, screening and diagnosis is key to providing the most effective treatment for individuals with depression.

Those who show signs of depression should talk to their health care provider. A primary health care professional can begin assessing your symptoms, establish a diagnosis, and discuss treatment options. They can bring in other professionals, such as psychiatrists and psychologists, if necessary.

A typical visit will have a health care provider asking questions about symptoms, such as:

  • What symptoms are you experiencing and when they began
  • Whether or not those symptoms interfere with your functioning (e.g., your responsibilities as an employee or student; or as a parent or spouse; or commitments to friends)
  • Any history with similar symptoms and previous treatment
  • Any physical health problems
  • Any current medications or substance use

To assist in the health care professional’s assessment and diagnosis, it’s recommended that you bring notes on what you have been feeling and when. It can be very helpful to bring a loved one to also relay their observations. The health care professional’s assessment will also include any physical health ailments, assessment of all medications, substance use, and may conduct a physical exam and lab tests, in addition to an interview.

How is Depression Treated?

Health care professionals treat major depressive disorder using one (or both) of the following methods:

  1. Medications, also called psychopharmacology
  2. Therapy, also called psychotherapy

Each treatment plan is based on the individual’s symptoms, history, and immediate and overall goals for recovery. The treatment plan may start with medications and/or therapy and will likely be adjusted over time based on symptom change, side effects, and goals. It may take some time and tweaking to find the perfect treatment plan for an individual. Working in partnership with your treatment team is essential.
What Causes Major Depressive Disorder?


Psychopharmacology, or medication-based treatment, is often considered as part of a treatment plan for major depressive disorder. Prescribed medications work for many people suffering from depression. These are called antidepressants. A mental health professional will help decide if antidepressants are the right course of action for your treatment plan—if you receive a prescription, be sure to ask exactly how you should take the medication.

Antidepressants typically take some time to start working. Individuals can begin to notice a benefit as soon as two weeks, but it often takes up to four to eight weeks in most cases.10 Antidepressants often start by relieving the milder symptoms, such as appetite or sleep problems, before improving the person’s mood. Some people describe feeling the medications protect them from becoming “too depressed.”

Treatment Plan

Finding the right medications and overall treatment plan for an individual’s specific case of depression can take some time. Some individuals do not fully respond to their first trial with antidepressant medications. In these situations, it is essential to revisit the diagnostic assessment, consider alternatives, and also ensure that the medication is being taken consistently. For symptoms of depression that persist, prescribers may increase the dose of the current antidepressant, change to a different antidepressant, or possibly add another medication to the current antidepressant. Other medications like lithium, bupropion, or atypical antipsychotic medications (aripiprazole, brexpiprazole, or quetiapine) are some examples of medications that can added to an existing antidepressant. For some individuals who don’t respond to these strategies, brain stimulation therapies, such as electroconvulsive treatment or repetitive transcranial stimulation, may be considered. Here are a few important points, to discuss with your treatment team as you begin antidepressants:

  • Gather instructions regarding the medications themselves (how much to take, when to take, what to do if you miss a dose, what side effects could be expected, etc.) and any interactions with specific foods, alcohol, substances, and other medications
  • Share if you are or plan to get pregnant. Balance the potential risks to the fetus and the potential risks not using antidepressant medication during pregnancy.
  • Always discuss with your health care professional before stopping any medications or if you have bothersome side effects.


Psychotherapy is one of the most common methods for treating individuals with depression. Also known as “talk therapy” or “counseling,” therapy helps people with depression understand the behaviors, emotions, and ideas as well as the life events that contribute to their depression, learn coping techniques and problem-solving skills, and regain a sense of control and pleasure in life.

Therapy sessions take place with a trained, licensed mental health professional, and they can be done either one-on-one or in group settings, depending on the individual’s needs.

The two most common forms of therapy for depression are cognitive behavioral therapy (CBT) and interpersonal therapy (IPT).

Cognitive behavioral therapy (CBT) helps individuals change thinking and behavior patterns byidentifying and altering inaccurate perceptions that they may have of themselves and the world around them. The focus is on what is presently happening in the individual’s life. Through exercises in the session as well as “homework” outside of sessions, individuals are helped to develop coping skills, whereby they can learn to change their own thinking, problematic emotions, and behavior.

Interpersonal therapy (IBT) focuses on behaviors and interactions with family and loved ones that directly impact the person’s mood. By helping individuals improve their communication skills within relationships, develop realistic expectations, improve self-esteem and establish support networks, Interpersonal therapy helps individual’s deal directly with the issues related to loss, relationship conflicts, and life identity/role issues.

Brain Stimulation Therapy

Electroconvulsive therapy (ECT) can be an effective treatment for major depressive disorder when an individual has not responded to other treatments. It is a procedure done under general anesthesia. The number of treatments for each person varies, but most people need 6 to 12 treatments, which are initially given three times per week.

Repetitive Transcranial Magnetic Stimulation (rTMS) is a non-invasive technique that uses a magnetic field to stimulate certain areas of the brain. Initially, sessions generally occur five days per week for several weeks.

What Can Individuals Do At Home To Help Their Depression?

What Can Individuals Do At Home To Help Their Depression?

Consulting a health care professional and staying consistent with their treatment plan is crucial for treating depression. However, there strategies you can use to supplement the treatment plan, that may help you further combat and manage your symptoms.


Here are some examples:

  • Know your triggers that might exacerbate symptoms and avoid those triggers, if possible
  • Acknowledge warning signs for onset or exacerbation of symptoms and reach out for support as early as possible
  • Fit in at least 30 minutes daily of any physical activity (could be a walk around the block; vacuuming your home; climbing the stairs in your building)
  • Revisit activities that previously brought you pleasure (e.g., eating out; reading; doing a puzzle; calling friends; watching a movie)
  • Focus on self-care, such as meditation; a haircut; a massage; a manicure
  • Set a sleep schedule (consistent bedtime and wake-up times)
  • Eat healthy, nutritious meals and snacks as much as possible
  • Avoid alcohol and drug use
  • Seek support from loved ones often

What Does Recovery From Depression Look Like?

As stated above, the risk of recurrence of a depressive episode progressively lowers over time. This means, that many individuals experience longer periods without an episode as they age. Additionally, following the treatment plan developed in partnership with your health care professional, will allow you to learn your triggers, develop successful coping, and establish supports, all of which will allow you to not only live with major depressive disorder, but actually thrive and have a full life.

Individuals with depression may inquire about collaborative care programs, which allow for an integrative approach to both mental health and physical health. As many of the symptoms of major depressive disorder also impact physical health, this can be a very impactful approach to treatment.

Questions About Depression?

Questions About Depression?

Looking for more information about depression?

Whether it’s for yourself, a family member, or a friend, you can find many resources in our Individuals and Families section. For clinicians, we recommend checking out the SMI Adviser Knowledge Base, which allows you to browse hundreds of evidence-based answers and resources.

For mental health clinicians, you can submit a question to learn more about evidence-based treatments, research, or where to find resources for individuals. Our national experts will provide you with a free consultation.


  1. Diagnostic and Statistical Manual of Mental Disorders: Fifth Edition, Text Revision, DSM-5-TR, American Psychiatric Association, 2022.
  2. Depression | NAMI: National Alliance on Mental Illness
  3. NMHI >> Depression
  4. Depression Statistics | Depression and Bipolar Support Alliance
  5. Depression Fact Sheet – WHO | World Health Organization
  6. What is Depression – National Institute of Mental Health
  7. Living Well With Major Depressive Disorder – SAMHSA | Substance Abuse and Mental Health Services Administration
  8. Depression and Anxiety – CDC | Centers for Disease Control and Prevention
  9. Is Depression Curable? – MHA | Mental Health America
  10. Trivedi, M. H., Rush, A. J., Wisniewski, S. R., Nierenberg, A. A., Warden, D., Ritz, L., Norquist, G., Howland, R. H., Lebowitz, B., McGrath, P. J., Shores-Wilson, K., Biggs, M. M., Balasubramani, G. K., Fava, M., & STAR*D Study Team (2006). Evaluation of outcomes with citalopram for depression using measurement-based care in STAR*D: implications for clinical practice. The American journal of psychiatry, 163(1), 28–40. https://doi.org/10.1176/appi.ajp.163.1.28

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