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Glossary of Terms

Reviewed by: HU Medical Review Board | Last reviewed: September 2023

Major depressive disorder, or MDD, is a common mental health condition. During your mental health journey with depression, it can be helpful to understand some common terms related to depression. Continue reading for a list of terms related to MDD.



Severe lack of energy or physical motivation, which is often seen in people with depression.1


Not being able to feel happy or interested in things that used to make you happy or excited. It is a common symptom of depression.1


Prescription drugs used to treat depression. Most antidepressant drugs act on chemicals that send messages from the brain, called neurotransmitters. Commonly prescribed antidepressants include selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs).2


A class of drugs prescribed for people who have symptoms of psychosis or as an add-on to support other medicines. These symptoms include delusions and hallucinations.1



A collection of movement-related symptoms that can greatly impact quality of life. Signs of catatonia include being unable to speak, freezing in uncomfortable positions, and mimicking the words or sounds of others. Some people with depression develop catatonia.3

Cognitive behavioral therapy (CBT)

A widely used therapeutic approach for treating depression. It helps people identify and change negative thought patterns and behaviors.1



A strongly held belief not based in reality.1


A serious mental health condition that involves strong feelings of sadness. It may also lead to a lack of interest in things a person used to enjoy. Depression affects a person’s ability to function in daily life. Severe depression is also called major depressive disorder (MDD).1,2


The fifth edition of a book called the Diagnostic and Statistical Manual of Mental Disorders. Doctors use this book to help them diagnose different mental health conditions, like major depressive disorder.1


A milder but long-lasting form of depression. Those with dysthymia feel sad and uninterested in things every day for a long time, usually 2 years or more.1


Electroconvulsive therapy (ECT)

A procedure done under general anesthesia. During ECT, mild electric currents are applied to the brain. This causes a brief seizure. Experts think this changes brain chemistry. It can quickly treat some mental health conditions, including depression.4



Seeing, hearing, or feeling the sensation of something that is not there.1


A feeling of having no expectation or belief that things will get better or improve in the future. It is a deep sense of despair that can be a symptom of depression.5


Major depressive disorder (MDD)

Also known as clinical depression. MDD is a mood disorder of persistent and severe sadness, hopelessness, and a lack of interest or pleasure in activities. It affects a person's thoughts, emotions, and physical well-being.1,2

Major depressive episode

Periods of 2 weeks or more in which a person has multiple symptoms of depression.3

Mental status exam (MSE)

A tool used to assess a person’s moods, thoughts, and feelings to help make a diagnosis of a mental health condition. A doctor may perform this assessment if a person shows signs of a mental health disorder.3

Monoamine oxidase inhibitors (MAOIs)

MAOIs are an older type of antidepressant medicine. They work by stopping an enzyme called monoamine oxidase. This helps increase levels of chemicals in the brain called neurotransmitters, including serotonin, norepinephrine, tyramine, and dopamine.6



Chemical messengers that carry signals from one cell to another. Experts think that imbalances in neurotransmitter levels play a role in the development of depression.1


Postpartum depression

Major depression that occurs after a person has given birth. This may also be called peripartum depression because it also can occur during pregnancy.3


Doctors who diagnose and treat mental, behavioral, and emotional conditions. They have a medical degree and license. They can prescribe therapy, medicine, or a combination of both.7


Mental health experts with doctoral degrees in psychology. They diagnose and treat mental disorders, but they do not prescribe drugs.7


A serious mental state marked by a disconnection from reality. People with psychosis may not know what is real and what is not. This can lead to hallucinations, which are hearing, seeing, or feeling things that are not there. It can also involve having delusions, which are strongly held false beliefs.1


Also known as talk therapy or counseling. This is a type of treatment for mental health problems. It involves conversations between a trained therapist or counselor and a single person, couple, or group.1



The return of depressive symptoms after a period of improvement (remission).1


A period during which the symptoms of depression lessen greatly or go away. Remission is the main goal of MDD treatment.1


The tendency to repetitively dwell on negative thoughts or events.8


Serotonin and norepinephrine reuptake inhibitors (SNRIs)

Antidepressants that increase the levels of both serotonin and norepinephrine in the brain. These drugs are used to treat depression and anxiety.9

Selective serotonin reuptake inhibitors (SSRIs)

Antidepressant drugs that work by increasing the availability of serotonin in the brain. They are commonly prescribed for MDD and related disorders.10


Negative thoughts, feelings, or ideas about certain people or groups because of something about them. Stigma can make others treat people with with mental health disorders unfairly, not understand them, and make them feel alone.1

Suicidal ideation

Having thoughts about wanting to end one's own life. It involves thinking about or planning ways to harm oneself. These thoughts can range from fleeting to more detailed and persistent ideas.1


Treatment-resistant depression

Depression that does not get better after a person has tried at least 2 different antidepressant drugs. People with treatment-resistant depression may turn to nondrug treatment options like psychotherapy and electroconvulsive therapy (ECT).2,3

Tricyclic antidepressants (TCAs)

Older antidepressant drugs that affect the levels of neurotransmitters in the brain. They are used less often today because there are newer drugs that may work better and lead to fewer side effects.11

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