A chemical imbalance in the brain is said to occur when there’s either too much or too little of certain chemicals, called neurotransmitters, in the brain. Neurotransmitters are natural chemicals that help facilitate communication between your nerve cells. Examples include norepinephrine and serotonin.

It’s often said that mental disorders, such as depression and anxiety, are caused by a chemical imbalance in the brain. The hypothesis is sometimes called the chemical imbalance hypothesis or chemical imbalance theory.

If you’re wondering if the symptoms you’re having are caused by a chemical imbalance, it’s important to know that there’s quite a bit of controversy surrounding this theory.

In fact, it’s been largely refuted by the medical community. Researchers argue that the chemical imbalance hypothesis is more of a figure of speech. It doesn’t really capture the true complexity of these disorders. In other words, mental disorders aren’t simply caused by chemical imbalances in the brain. There’s a lot more to them.

The idea that mental disorders are caused by a chemical imbalance in the brain was first proposed by scientists in the late 1950s. Research at the time had focused on the role that chemicals in the brain play in depression and anxiety.

These researchers hypothesized that lower-than-normal levels of neurotransmitters can lead to symptoms such as:

  • feelings of sadness, helplessness, worthlessness, or emptiness
  • overeating or loss of appetite
  • insomnia or sleeping too much
  • restlessness
  • irritability
  • a feeling of impending doom or danger
  • lack of energy
  • distancing yourself from others
  • feeling numbness or lacking empathy
  • extreme mood swings
  • inability to concentrate
  • thoughts of hurting yourself or others
  • being unable to carry out day-to-day activities
  • hearing voices in your head
  • alcohol or drug misuse

The exact cause of mental disorders 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 unproven and often cited as an explanation for mental disorders. It states that these conditions are caused by an imbalance of neurotransmitters between nerve cells in the brain. For example, depression is said to be a result of having too little serotonin in the brain. But the theory doesn’t explain how these chemicals become unbalanced in the first place.

As Harvard Medical School reports, there are likely millions of different chemical reactions occurring in your brain at any given time. These are responsible for a person’s mood and overall feelings. There would be no way to tell if someone truly had a chemical imbalance in their brain at a given time.

The most common evidence used to support the chemical imbalance theory is the effectiveness of antidepressant medications. These medications work by increasing the amounts of serotonin and other neurotransmitters in the brain.

But, just because a person’s mood can be elevated with drugs that increase brain chemicals doesn’t mean that their symptoms were caused by a deficiency in that chemical in the first place. It’s also possible that low serotonin levels are just another symptom of depression, not the cause.

Many people with depression don’t get better after being treated with these types of antidepressants. One study estimates that current antidepressants on the market only work in about 60 percent of those with depression.

There are no reliable tests available to find out if you have a chemical imbalance in your brain. Tests that use urine, saliva, or blood to measure neurotransmitters in the brain likely won’t be very accurate.

Not all neurotransmitters are produced in the brain. Currently marketed tests won’t be able to distinguish between neurotransmitter levels in your brain and neurotransmitter levels in the body. In addition, neurotransmitter levels in your body and brain are constantly and rapidly changing. This makes such tests unreliable.

Diagnosing mental disorders

Mental disorders aren’t diagnosed with chemical tests. Your treatment plan won’t be guided by such tests either. Your doctor may order blood tests to rule out other conditions, such as a thyroid disorder or vitamin deficiency, which can trigger symptoms of a mental disorder.

If no underlying illness is found, you’ll likely be referred to a mental health professional, such as a psychiatrist or psychologist. They’ll perform a psychological evaluation. This includes a series of questions about your thoughts, feelings, eating and sleeping habits, and daily activities.

There are several medications available that are thought to work by changing the levels of certain brain chemicals. These drugs alter levels of either dopamine, noradrenaline, serotonin, or norepinephrine. Some work on a combination of two more of these chemicals.

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). This includes 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), prevent your brain from reabsorbing the neurotransmitters norepinephrine and dopamine.
  • Monoamine oxidase inhibitors (MAOIs). MAOIs keep your brain from breaking down 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 disorders, there are likely many factors at play. It’s difficult to tell whether a particular drug will ensure a cure.

For some people, depression and other mental disorders are episodic. This means that the symptoms come and go. Medications might be able to help manage 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 disorder, talk therapy techniques are also important. Psychotherapy helps to convert your thinking and behavioral patterns into healthier ones. One example is called cognitive-behavioral therapy. This type of therapy can prevent your depression from returning once you’re feeling better.

Mental disorders aren’t as simple as having a chemical imbalance in the brain. There’s little evidence to prove that an imbalance in certain brain chemicals is the cause of any type of mental disorder.

If you’re experiencing any of the signs and symptoms of a mental disorder, it’s important to see a doctor for a diagnosis. Don’t hesitate to get help. Once you get a diagnosis, you may need to try many different medications or combinations of medications before you find the one that works for you.

Your doctor 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 six weeks.