A chemical imbalance in the brain is said to occur when the brain has either excessive or insufficient chemicals, called neurotransmitters.
Neurotransmitters are natural chemicals that help ease the communication between your nerve cells. Examples include norepinephrine and serotonin.
The hypothesis is sometimes called the chemical imbalance hypothesis or chemical imbalance theory.
If you wonder whether the symptoms you’re experiencing are caused by a chemical imbalance, it’s important to know that controversy surrounds this theory. In fact, the medical community has largely disproven it.
Researchers argue that the chemical imbalance hypothesis is more of a figure of speech. It doesn’t capture the complexity of these conditions.
In other words, mental health conditions aren’t precisely caused by chemical imbalances in the brain. There’s a lot more to them.
Scientists in the late 1950s proposed the idea that mental health conditions are caused by a chemical imbalance in the brain.
Research at the time focused on the role that chemicals in the brain play in depression and anxiety.
These researchers hypothesized that insufficient levels of neurotransmitters can lead to symptoms such as:
- feelings of sadness, helplessness, worthlessness, or emptiness
- overeating or a loss of appetite
- insomnia or sleeping too much
- a feeling of impending doom or danger
- a lack of energy
- distancing yourself from others
- a feeling of numbness or a lack of empathy
- extreme changes in mood
- thoughts of hurting yourself or others
- difficulty carrying out day-to-day activities
- a feeling of hearing voices in your head
- alcohol or drug misuse
- difficulty concentrating
The exact cause of mental health conditions is still unclear. Researchers believe that genetics as well as environmental and social factors, such as stress or trauma, play a role.
The chemical imbalance theory is disproven, yet it’s often presented as an explanation for mental health conditions.
It states that these conditions are caused by an imbalance of neurotransmitters between nerve cells in the brain.
For example, depression is said to result from insufficient levels of serotonin in the brain. But the theory doesn’t explain how these chemicals become imbalanced.
Harvard Medical School reports that there are likely millions of chemical reactions occurring in the brain. These reactions are responsible for presenting a person’s mood and overall feelings.
The millions of reactions occurring makes it impossible to determine if someone is experiencing a chemical imbalance in their brain.
The most common evidence used to support the chemical imbalance theory is the effectiveness of antidepressant medications.
Antidepressant medications work by increasing the levels of serotonin and other neurotransmitters in the brain.
However, if a person’s mood can be elevated with help from medications to increase brain chemicals, this doesn’t mean that the symptoms necessarily come from a chemical deficiency.
It’s also possible that low serotonin levels are just another symptom of depression, not the cause.
A 2007 research review showed that these types of medications were ineffective for treating people living with depression.
One study estimates that current antidepressants on the market are only effective for treating about
There are no reliable tests available to help diagnose a chemical imbalance in the brain.
Tests that use urine, saliva, or blood to measure neurotransmitters in the brain are unlikely to be accurate.
Not all neurotransmitters are produced in the brain. The tests that are currently marketed don’t distinguish between neurotransmitter levels in your brain and in the rest of your body.
In addition, neurotransmitter levels in your body and brain are constantly and rapidly changing. This makes such tests unreliable.
Diagnosing mental health conditions
Mental health conditions aren’t determined by using chemical tests. Your treatment plan won’t be guided by such tests either.
Your healthcare provider may order blood tests to rule out other conditions, such as a thyroid disorder or vitamin deficiency. Both conditions can trigger symptoms of a mental health condition.
If an underlying illness is not determined from the tests, your healthcare provider will likely refer you to a mental health professional, such as a psychiatrist or psychologist. They’ll perform a psychological evaluation.
The evaluation will include a series of questions about your:
- eating and sleeping habits
- daily activities
There are several medications available that are thought to work by changing the levels of brain chemicals through blocking reabsorption.
Blocking reabsorption increases the level of neurotransmitters that are available for your nerves to use. This will activate your nerve receptors for a longer time. These medications alter neurotransmitter levels of either:
- norepinephrine, also called noradrenaline
Some medications work on a combination of two more of the chemicals above.
Examples of these medications include:
- Selective serotonin reuptake inhibitors (SSRIs). SSRIs work by blocking the reabsorption of serotonin. Examples are fluoxetine (Prozac), paroxetine (Paxil), and citalopram (Celexa).
- Serotonin-norepinephrine reuptake inhibitors (SNRIs). They include duloxetine (Cymbalta) and venlafaxine (Effexor XR). SNRIs work by blocking the reabsorption of both serotonin and norepinephrine, leading to increased levels of these two chemicals in the brain.
- Tricyclic antidepressants (TCAs). Examples are imipramine (Tofranil) and nortriptyline (Pamelor). TCAs block the reabsorption of noradrenaline and serotonin.
- Norepinephrine-dopamine reuptake inhibitors (NDRIs). NDRIs, such as bupropion (Wellbutrin), block reabsorption of the neurotransmitters norepinephrine and dopamine.
- Monoamine oxidase inhibitors (MAOIs). MAOIs block the reabsorption of norepinephrine, serotonin, and dopamine. These medications, including isocarboxazid (Marplan) and phenelzine (Nardil), are not as popular as other types of antidepressants.
When it comes to mental health conditions, there are likely many factors at play. It’s difficult to determine whether a particular treatment will ensure a cure.
For some people, depression and other mental health conditions are episodic, which means that the symptoms come and go.
Medications might be able to help manage your symptoms, but the disorder may take a long time to go into remission. Symptoms can also come back later on.
While taking medications for a mental health condition, talk therapy techniques are also an important addition to your treatment plan.
During these therapy sessions, you will work with a mental health professional to use techniques that may help you manage your depression or prevent it from returning once you’re feeling better.
There’s little evidence to determine that an imbalance in brain chemicals is the cause of any type of mental health condition.
If you’re experiencing any of the signs and symptoms of a mental health condition, it’s important to contact a healthcare provider for a diagnosis.
Once you receive a diagnosis from your healthcare provider, you may need to try different treatments or combinations of treatments before you find the one that works for you.
Your healthcare provider will need to take into account several variables when determining a treatment plan.
Patience is key. Once you find the right treatment, most people show improvement in their symptoms within 6 weeks.