A team of researchers from the University of Florida (UF) has identified a common amino acid that they believe may play a role in causing major depressive disorder (MDD) and certain related conditions.
The researchers published their findings in March 2023 on the website of the journal Science. In addition to helping clinicians gain a greater understanding of why some people have an increased risk for MDD, the study may also lead to the development of more effective antidepressant medications.
What Is Major Depressive Disorder?
Before we delve into a possible biological cause of major depressive disorder, let’s take a moment to discuss exactly what this mental health condition is.
As established in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), a person must experience at least five of the following symptoms during a two-week period to receive a clincal diagnosis for major depressive disorder:
- Sadness, emptiness, hopelessness, or other signs of depressed mood
- Diminished interest in and lack of pleasure from most activities
- Significant unintentional weight gain or loss
- Abnormal sleeping patterns (either insomnia or hypersomnia)
- Sense of either restlessness or slowed physical movement
- Persistent fatigue
- Sense of worthlessness or inappropriate guilt
- Difficulty thinking, concentrating, and/or making decisions
- Recurring thoughts of death and dying
In a person with major depressive disorder, symptoms are severe enough to cause considerable distress and undermine their ability to function at work, in school, or other important areas of life.
Some people may only have one major depressive episode, while others may experience recurring episodes. Given the criteria listed above, it’s not difficult to understand how major depressive disorder can have a profound negative impact on a person’s ability to live a productive and satisfying life.
The Scope of the Problem
MDD is one of the most common mental illnesses in the United States and throughout the rest of the world. The National Institute of Mental Health (NIMH) has reported the following statistics about the prevalence and impact of major depressive disorder in the U.S.:
- About 8.4% of adults in the U.S. – or about 21 million people aged 18 and above – had a major depressive episode in the previous 12 months.
- Among those who had symptoms of major depressive disorder last year, more than 70% (or about 14.8 million people) experienced serious impairment as scored on the Sheehan Disability Scale.
- MDD is significantly more common among adult women (10.5%) than among adult men (6.2%).
- Among adults, major depressive disorder is most common in the 18-25 age group (17%).
- Experts estimate that about two-thirds of people with depression received professional care in the past year. This means that about 7 million people with depression did not get the help they needed.
To underscore the seriousness of this problem, the Depression and Bipolar Support Alliance (DBSA) reports that 20% of people with untreated depressive disorders attempt suicide at least once. The DBSA also notes that depression is a factor in more than two-thirds of all deaths by suicide in the U.S.
A Possible Cause
Recently, a team of researchers from the Scripps Institute for Biomedical Innovation & Technology announced that they identified a common amino acid associated with major depressive disorder and certain other mood disorders.
In March 2023, the Scripps team published their findings in the journal Science.
As described in a March 31, 2023, article on the University of Florida Health (UF Health) website, these findings indicate that signals delivered to the brain by an amino acid called glycine may be responsible for some cases of MDD.
What Is Glycine?
According to an article in the journal Oxidative Medicine and Cellular Longevity, glycine is the “most important and simple, nonessential amino acid in humans, animals, and many mammals.” Representing about 11% of the amino acid content in a healthy human body, glycine plays an essential role in the production of proteins.
Glycine is naturally produced by the body. It can also be acquired through certain foods, such as meat, fish, legumes, and dairy products. The article we cite above also notes that supplemental glycine may be used to treat people who have cardiovascular disease, some cancers, diabetes, certain inflammatory diseases, and obesity.
Glycine & Major Depressive Disorder
The Scripps team discovered the link between glycine and major depressive disorder while researching how sensors on brain cells receive and transmit signals, and how those signals affect the cells themselves.
Here’s a quick overview of their efforts, as described in the UF Health article:
- Scripps researchers have studied brain receptors for more than 15 years.
- In 2018, the team found that mice without the gene for a certain brain receptor (GPR158) showed decreased likelihood of developing depressive symptoms after experiencing chronic stress.
- In 2021, the team discovered that GPR158 is an amino acid receptor. Further research identified glycine as the amino acid that interacts with this receptor.
- When glycine binds to GPR158, it activates a molecule that causes certain parts of the brain to slow down. The researchers believe that this is a factor in MDD and other mood disorders.
Kirill Martemyanov, PhD, one of the study authors, said the findings may lead to more effective medications to treat depressive disorders.
“There are limited medications for people with depression,” Martemyanov said in the UF Health article. “Most of them take weeks before they kick in, if they do at all. New and better options are really needed. … If we can target this with something specific, it makes sense that it could help.”
Treatment Options for Major Depressive Disorder
Though the research described in this post may lead to more refined pharmacological solutions for people who have MDD and other mood disorders, medication is typically just one part of effective treatment for these complex mental health concerns.
Though medications may ease certain symptoms, they cannot address the behavioral, academic, occupational, and social aspects of MDD and other mood disorders.
Depending on the duration of MDD and the severity of symptoms, people may experience depression-related setbacks in school and at work, problems in their relationships, and difficulty establishing and maintaining an independent lifestyle.
To properly address these and other common effects of major depressive disorder, therapy and education can be essential. Certain adjunct support services are also beneficial.
For example, at Crownview Psychiatric Institute, personalized treatment for depression typically includes the following elements:
- Medication to help patients manage their symptoms
- Therapeutic programming that reflects the principles established in the Unified Protocol for Transdiagnostic Treatment of Emotional Disorders
- Educational sessions that focus on both home skills and work skills
- Adjunct services such as transcranial magnetic stimulation (TMS) therapy, stellate ganglion block, NAD IV therapy, and ketamine treatment
- Wraparound support to help patients connect with community-based services and resources.
- A vibrant treatment environment that helps patients form healthy relationships with others while rediscovering their own self-worth
To learn more about treatment for major depressive disorder, other types of depression, and other complex mental health challenges at Crownview Psychiatric Institute, please visit our Admissions page or call us at your convenience.
Gianna Melendez
Jodie Dahl, CpHT