What Is Major Depressive Disorder?

What Is Major Depressive Disorder?

Depression is a serious mental illness that impacts more than 300 million people worldwide, according to the World Health Organization. In the United States alone, this amounts to around 19.4 million adults, or about 7.8% of the adult population, as of 2009. For many of these people, depression takes the form of major depressive disorder (MDD), or “clinical depression.”

For many people who experience MDD, it can be a challenge to live a normal life, and things like maintaining relationships, staying productive at work, and personal care can be extremely difficult or impossible. This article will go over what MDD is, what causes it, and treatment methods.

Major Depressive Disorder— Who It Effects 

When most people talk about “depression,” they are usually referring to major depressive disorder. Otherwise known as clinical depression, MDD is characterized by a persistent low mood, or “depressed state,” that lasts for at least two weeks.

MMD is one of the leading causes of disability worldwide as it can dramatically decrease a person’s ability to function and live a normal life. It is the culprit of about 850,000 deaths every year, often the result of being left untreated.

While every demographic can be affected by MMD, it is more common among women, people who are mixed race, and people who are between the ages of 18 and 25.

Regardless of your age, gender, race, socioeconomic status, or any other demographic factor, anyone can get MDD and experience a reduced quality of life as a result.

Symptoms of Major Depressive Disorder

Major depressive disorder’s defining characteristic is that it causes a persistent feeling of sadness, hopelessness, or loss of interest in life and activities that normally give you pleasure.

In order to be diagnosed with MDD, a person must experience at least five of the following symptoms, according to the DSM-5’s criteria:

  • A depressed mood. This can be expressed as feeling sadness, emptiness, hopelessness, or even irritability.
  • A markedly diminished interest or pleasure in all, or almost all, activities.
  • Significant weight loss or gain that is not due to dieting or other explanations. This can also manifest as a decreased or increased appetite.
  • Insomnia or hypersomnia.
  • Fatigue or loss of energy.
  • Feeling worthless or guilty even when guilt is unjustified or inappropriate.
  • Decreased concentration or indecisiveness.
  • Frequent thoughts of death or suicide.

These symptoms must occur on a fairly frequent daily or nearly daily basis over the course of a two-week period or longer.

What’s the Difference Between MDD and Feeling Sad?

Like many mental illnesses, MDD is characterized by extreme feelings and emotional states. While it’s normal to feel down, sad, or just off for a few days or in reaction to a demotivating event (such as losing an opportunity or making a mistake), MDD is more severe and persistent than that.

MDD also frequently happens in the absence of any obvious trigger. Unlike regular feelings of sadness that may appear as a result of something bad happening, clinical depression is persistent even in situations that should make someone feel happy, like being on vacation or spending time with friends.

Causes of Major Depressive Disorder

The root cause of MDD is unknown, but it is likely the result of a complex interaction between biological and environmental factors.

Biological causes may include:

  • Differences in the Structures and Functioning of the Brain: While the specifics and significance of this are not yet known, numerous studies have shown that gray and white matter in the brain is altered in patients with major depression. This is especially true in regions like the frontal lobe, hippocampus, amygdala, and temporal lobe.
  • Chemical Imbalances in the Brain: While this is yet another area of study that hasn’t reached too many definitive conclusions, it has been observed that patients with depression have different levels of dopamine, serotonin, and norepinephrine than healthy individuals.
  • Disruptions or Irregularities in Hormones: Certain hormonal factors, such as pregnancy, menopause, and thyroid problems, have shown to be involved in triggering depression.
  • Genetics: Many people who have depression are likely to have family members who also struggle with mental illness.

Environmental causes of depression may include:

  • Stress: Stressful life events or traumas, such as the loss of a loved one, job loss, or financial stress may cause temporary, acute depressive episodes or may trigger long-term depression, such as MDD.
  • Chronic Medical Conditions: While certain medical conditions can biologically trigger depression as well, many conditions that are biologically unrelated to depression can also play a role in the development of depression because of the stress and trauma associated with dealing with these conditions.
  • Disposition: Certain personality traits, such as low self-esteem, perfectionism, and being overly dependent or independent, can also be factors to developing depression, as they can cause someone to fall into thinking patterns that lead to feelings of hopelessness or worthlessness.

For most people with MDD, the cause of the condition is not singular but is rather the result of a complex mix of biological and environmental factors.

Treatment Methods for Major Depressive Disorder

Mild or moderate depression can often be treated successfully with psychotherapy, medication, or a combination of the two. In more severe cases, treatment may need to be intensive and require hospitalization.


While there are several types of psychotherapy a patient may use to help ease symptoms of depression, the most common that’s used for MDD is cognitive-behavioral therapy (CBT). CBT helps patients identify and change negative thinking patterns that contribute to their depression.

It is beneficial because it teaches patients skills that they can use for the rest of their lives to manage their depression. CBT has been found to be especially effective when used in combination with medication.


There are several types of medication that can be prescribed to help ease the symptoms of MDD. The most common are antidepressants, which work by correcting chemical imbalances in the brain that are thought to contribute to depression.

Other types of medication that may be used are mood stabilizers, antipsychotics, and anti-anxiety medications.

Alternative Treatments

For many patients with MDD, traditional psychotherapy and medication simply isn’t enough. These patients have what is called “treatment-resistant depression,” and for them, other options need to be considered.

One option that has recently seen great success is ketamine. Ketamine is a medication that’s typically used as an anesthetic, but it has also been shown to be effective in treating depression, especially in patients who have not seen results from other treatments.

Ketamine works by decreasing levels of glutamate, which is a key neurotransmitter in the brain. By blocking glutamate pathways, ketamine counteracts the overactivation of glutamate receptors that can lead to long-term depression.

Ketamine has also shown to be highly effective at triggering the rapid growth of new neurological connections, which may regenerate neurons that have died off and triggered depression as a result.

If you are interested in learning more about how ketamine works to help patients with treatment-resistant depression, you can visit Edelica Health.

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