A chemical imbalance in the brain occurs when a person has either too little or too much of certain neurotransmitters.

Neurotransmitters are the chemical messengers that pass information between nerve cells. Examples of neurotransmitters include serotonin, dopamine, and norepinephrine.

People sometimes call serotonin and dopamine the "happy hormones" because of the roles that they play in regulating mood and emotions.

A popular hypothesis is that mental health disorders, such as depression and anxiety, develop as a result of chemical imbalances in the brain.

While this theory may hold some truth, it runs the risk of oversimplifying mental illnesses. In reality, mood disorders and mental health illnesses are highly complex conditions that affect 46.6 million adults living in the United States alone.

In this article, we discuss conditions with links to chemical imbalances in the brain, myths surrounding this theory, possible treatment options, and when to see a doctor.

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Many factors may contribute to a person's risk of mental illness.

It is a popular myth that chemical imbalances in the brain are solely responsible for causing mental health conditions.

Although chemical imbalances in the brain seem to have an association with mood disorders and mental health conditions, researchers have not proven that chemical imbalances are the initial cause of these conditions.

Other factors that contribute to mental health conditions include:

  • genetics and family history
  • life experiences, such as a history of physical, psychological, or emotional abuse
  • having a history of alcohol or illicit drug use
  • taking certain medications
  • psychosocial factors, such as external circumstances that lead to feelings of isolation and loneliness

While some studies have identified links between distinct chemical imbalances and specific mental health conditions, researchers do not know how people develop chemical imbalances in the first place.

Current biological testing also cannot reliably verify a mental health condition. Doctors do not, therefore, diagnose mental health conditions by testing for chemical imbalances in the brain. Instead, they make a diagnosis based on a person's symptoms and the findings of a physical examination.

Research has linked chemical imbalances to some mental health conditions, including:

Depression

Depression, also called clinical depression, is a mood disorder that affects many aspects of a person's life, from their thoughts and feelings to their sleeping and eating habits.

Although some research links chemical imbalances in the brain to depression symptoms, scientists argue that this is not the whole picture.

For example, researchers point out that if depression were solely due to chemical imbalances, treatments that target neurotransmitters, such as selective serotonin reuptake inhibitors (SSRIs), should work faster.

The symptoms of depression vary widely among individuals, but they can include:

  • persistent feelings of sadness, hopelessness, anxiety, or apathy
  • persistent feelings of guilt, worthlessness, or pessimism
  • loss of interest in formerly enjoyable activities or hobbies
  • difficulty concentrating, making decisions, or remembering things
  • irritability
  • restlessness or hyperactivity
  • insomnia or sleeping too much
  • changes in appetite and weight
  • physical aches, cramps, or digestive problems
  • thoughts of suicide

It is possible to develop depression at any age, but symptoms usually begin when a person is in their teenage years or early 20s and 30s. Women are more likely than men to experience depression.

Many different types of depression exist. These include:

The dramatic hormonal changes that take place after giving birth are among the factors that can increase a woman's risk of developing postpartum depression. According to the National Institute of Mental Health, 10–15% of women experience postpartum depression.

Bipolar disorder

Bipolar disorder is a mood disorder that causes alternating periods of mania and depression. These periods can last anywhere from a few days to a few years.

Mania refers to a state of having abnormally high energy. A person experiencing a manic episode may exhibit the following characteristics:

  • feeling elated or euphoric
  • having unusually high levels of energy
  • participating in several activities at once
  • leaving tasks unfinished
  • talking extremely fast
  • being agitated or irritable
  • frequently coming into conflict with others
  • engaging in risky behavior, such as gambling or drinking excessive quantities of alcohol
  • a tendency to experience physical injuries

Severe episodes of mania or depression can cause psychotic symptoms, such as delusions and hallucinations.

People who have bipolar disorder can experience distinct changes in their mood and energy levels. They may have an increased risk of substance abuse and a higher incidence of certain medical conditions, such as:

The exact cause of bipolar disorder remains unknown. Researchers believe that changes in the dopamine receptors — resulting in altered dopamine levels in the brain — may contribute to the symptoms of bipolar disorder.

Anxiety

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A person with an anxiety disorder may experience excessive worry.

Many people experience occasional anxiety when they face significant life changes, problems at home, or important projects at work.

However, people who have an anxiety disorder often experience persistent anxiety or excessive worry that worsens in response to stressful situations.

According to the authors of a 2015 review article, evidence from neuroscience research suggests that the gamma aminobutyric acid (GABA) neurotransmitter may play a crucial role in anxiety disorders.

The GABA neurotransmitter reduces neuronal activity in the amygdala, which is the part of the brain that stores and processes emotional information.

GABA is not the only neurotransmitter that anxiety disorders involve. Other neurotransmitters that may contribute to these disorders include:

  • serotonin
  • endocannabinoids
  • oxytocin
  • corticotropin-releasing hormone
  • opioid peptides
  • neuropeptide Y

Doctors can prescribe a class of medications called psychotropics to rebalance the concentration of particular neurochemicals in the brain.

Doctors use these medications to treat a range of mental health conditions, including depression, anxiety, and bipolar disorder.

Examples of psychotropics include:

  • Selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine (Prozac), citalopram (Celexa), and sertraline (Zoloft).
  • Serotonin-norepinephrine reuptake inhibitors (SNRIs), including venlafaxine (Effexor XR), duloxetine (Cymbalta), and desvenlafaxine (Pristiq).
  • Tricyclic antidepressants (TCAs), such as amitriptyline (Elavil), desipramine (Norpramin), and nortriptyline (Pamelor).
  • Benzodiazepines, including clonazepam (Klonopin) and lorazepam (Ativan).

According to 2017 research, antidepressants improved symptoms in an estimated 40–60% of individuals with moderate-to-severe depression within 6–8 weeks.

While some people experience reduced symptoms within a few weeks, it can sometimes take months for others to feel the effects.

Different psychotropics have varying side effects. People can discuss the benefits and risks of these medications with their doctor.

The side effects of psychotropic medications can include:

Suicide prevention

  • If you know someone at immediate risk of self-harm, suicide, or hurting another person:
  • Call 911 or the local emergency number.
  • Stay with the person until professional help arrives.
  • Remove any weapons, medications, or other potentially harmful objects.
  • Listen to the person without judgment.
  • If you or someone you know is having thoughts of suicide, a prevention hotline can help. The National Suicide Prevention Lifeline is available 24 hours a day at 1-800-273-8255.

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If a person experiences anxiety and mood changes every day for longer than 2 weeks, they should consider speaking to their doctor.

Anxiety and mood changes can occur for a variety of reasons.

These symptoms should not cause alarm if they are mild and resolve within a few days.

However, people may wish to consider speaking with a doctor or trained mental health professional if they experience emotional, cognitive, or physical symptoms every day for more than 2 weeks.

Mental health is complex and multifaceted, and numerous factors can affect a person's mental well-being.

Although chemical imbalances in the brain may not directly cause mental health disorders, medications that influence the concentration of neurotransmitters can sometimes provide symptom relief.

People who experience signs and symptoms of a mental health problem for more than 2 weeks may wish to speak to a doctor.