What Is the Biochemical Basis of Depression?
Verywell / Ellen Lindner
There are several theories aboutwhat causes depression.
More recent findings indicate that depression is likely not the result of chemical imbalances in the brain.
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However, the belief that chemical imbalances are responsible for causing depression is widely held by the American public.
One survey found that nearly 85% of respondents believed that such imbalances were the likely cause of depression.
Sometimes, people with depression relate the condition to a specific factor, such as atraumatic eventin their life.
However, it’s not uncommon for people who are depressed to be confused about the cause.
They may even feel theydon’t have “a reason” to be depressed.
In these cases, learning about the theories of what causes depression can be helpful.
According to this idea, restoring the balance of brain chemicals could help alleviate symptoms.
This is where the differentclasses of antidepressant medicationsmay come in.
Many antidepressants alter levels of certain neurotransmitters in the brain.
The “serotonin hypothesis” suggested that low levels of this neurotransmitter were linked to depression.
The idea was that increasing serotonin levels could help improve mood and relieve symptoms of depression.
A study published in a 2023 issue of the journalMolecular Psychiatryfound further reason to doubt this explanation.
The research indicated there is little evidence to suggest that depression is because of chemical imbalances in the brain.
What proves to be an effective treatment for one person with depression may not work for someone else.
Depression is a multi-faceted condition.
Get our printable guide to help you ask the right questions at your next doctor’s appointment.
What Are Neurotransmitters?
Put simply, neurotransmitters are chemical messengers in the brain.
The space between two nerve cells is called thesynapse.
For example, serotonin receptors pick up serotonin molecules.
The chemical theory of depression suggested that imbalances in brain chemistry were a primary cause of depression.
However, recent findings found no evidence to support this idea.
While research indicates that serotonin levels may not cause depression, other neurotransmitters and interactions may play a part.
Dopamine is believed to play an essential role in a variety of conditions affecting the brain, includingParkinson’sandschizophrenia.
Norepinephrine
Norepinephrine is both a neurotransmitter and a hormone.
It plays a role in the “fight or flight response” along with adrenaline.
It helps send messages from one nerve cell to the next.
Schildkraut proposed depression comes up whenever there is too little norepinephrine in specific brain circuits.
Alternatively,maniaresults when too much of this neurotransmitter is in the brain.
There is evidence that supports the hypothesis; however, it has not gone unchallenged by researchers.
For one, changes in norepinephrine levels do not affect mood in every person.
Further, medications specifically targeting norepinephrine may alleviate depression in some people but not others.
Serotonin
Another neurotransmitter is serotonin or the “feel good” chemical.
As their name implies, these medications specifically act on serotonin molecules.
Researchers have looked into serotonin’s role in mood disorders for almost 30 years.
These substances produceside effects, such as dry mouth, blurry vision, constipation, and urinary hesitancy.
Low levels of neurotransmitters can result when there is a breakdown anywhere in the process.
For some people, antidepressants combined with psychotherapy prove especially effective for addressing their symptoms.
To complicate treatment further, medication does not always work for people with depression.
Whatever might be causing your symptoms, depression affects your internal and external life.
Therefore, medication alone may not be sufficient to address all the ways in which depression can affect you.
For example, stress may contribute to low levels of certain neurotransmitters.
For more mental health resources, see ourNational Helpline Database.
Even inflammation is being explored as a potential contributing factor.
Not all the research has been negative, though.
More often than not, an interdisciplinary approach is needed.
At the very least, every person dealing with depression needs and deserves a support team.
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