Bipolar disorder is a mental health condition that can cause extreme changes in mood. It is also associated with various structural and functional changes in the brain.

People with bipolar disorder may experience extreme shifts in mood, meaning that they can rapidly move from feeling depressed to having an episode of mania. The condition also affects concentration, energy, and decision making.

Former names for bipolar disorder include manic-depressive illness and manic depression. The episodes of either high mood and elation or low mood and depression can persist for weeks or longer.

This article looks at the differences between the brains of people with bipolar disorder and those of people without the condition. It also answers some commonly asked questions about bipolar disorder.

Bipolar disorder affects multiple structures in the brain, as well as how the organ functions.

Experts believe that bipolar disorder is associated with the smaller size of certain regions of the brain and with changes in the brain’s chemicals. It can also cause changes in thinking and hallucinations.

In some cases, it is unknown whether changes to the brain cause bipolar disorder or result from the condition.

What happens in the brain of someone with bipolar disorder?

The brain of a person with bipolar disorder can differ in many ways from the brain of a person without the disorder.

One contributing factor to bipolar disorder is an imbalance of certain chemicals in the brain called neurotransmitters. A chemical imbalance may cause different symptoms in different people.

Experts also believe that there are structural changes in the brain of somebody living with bipolar disorder, with certain regions of the brain experiencing a reduction in size.

Bipolar disorder can affect all regions of the brain, both structurally and functionally.

Notable areas of the brain that bipolar disorder affects include:

  • The prefrontal cortex: This part of the brain plays an important role in mood-related disorders and is responsible for cognitive control, impulsivity, and attention.
  • Gray matter: This is the outermost part of the brain. Gray matter processes information and is important for movement, emotions, and memory.
  • The hippocampus: This part of the brain plays a role in emotions and memory.

Bipolar disorder may reduce gray matter volume

Gray matter plays an important role in enabling humans to function each day. It is present in the central nervous system in both the brain and spinal cord. Gray matter contributes in some way to every aspect of human life.

A 2016 meta-analysis found a significantly lower volume of gray matter in the brains of people with bipolar disorder compared with those of people without the condition. This was also true for people with major depressive disorder.

These reductions in gray matter happened in areas of the brain associated with mood regulation, information processing, and awareness of bodily states.

In a 2021 study, researchers did not find consistent differences in brain volume between people with or without bipolar disorder. However, they did report an association between a higher frequency of manic and hypo-manic episodes and gray matter loss in the brain, mainly in the prefrontal cortex.

Bipolar disorder may shrink parts of the hippocampus

The hippocampus is an area of the brain that is important for emotional control, including the stress response and memory formation and retrieval.

In people with bipolar disorder, parts of the hippocampus may be smaller than in people without a mood disorder, although research findings have not always been consistent.

A 2017 study explored whether hippocampal volume was related to mood disorders and mood episodes. The researchers used MRI scans to view the brains of study participants and measure the volumes of regions of the brain.

The study involved 152 people who did not have a mood disorder, 133 who had bipolar disorder, and 86 who had major depressive disorder.

The researchers compared the MRI scans and found that certain parts of the hippocampus were smaller in people with bipolar disorder than in those in the other two groups.

They noted that these size reductions in areas of the hippocampus were most distinct in people who had bipolar I disorder, which typically entails periods of extreme mania. In fact, the reduced hippocampal volume was most significant in people who had also experienced the most episodes of mania.

More recently, a 2022 study also concluded that reduced hippocampal gray matter volume is a common feature of people with bipolar disorder.

Bipolar disorder may change the brain’s chemical balance

Experts believe that bipolar disorder is associated with a chemical imbalance in the brain.

Brain chemicals called neurotransmitters help deliver messages between areas of the brain. An imbalance of these chemicals may cause symptoms of bipolar disorder.

However, it is unknown whether this imbalance causes bipolar disorder or occurs because of it.

The three main neurotransmitters that bipolar disorder may affect are:

Symptoms of high norepinephrine levels

In people with bipolar disorder, high and low levels of norepinephrine — also called noradrenaline — are associated with periods of mania and depressive episodes, respectively.

During an episode of mania, a person with bipolar disorder may experience:

  • high energy
  • intense feelings of happiness, elation, or joy
  • having new ideas or plans
  • talking quickly
  • feeling easily agitated or annoyed
  • hallucinations
  • delusions or illogical thinking
  • being easily distracted
  • avoidance of sleep
  • impulsive choices, such as spending large amounts of money
  • not eating

Symptoms of low serotonin levels

Low levels of serotonin are associated with depression and low mood.

People with bipolar disorder having a depressive episode may experience:

  • low energy
  • suicidal thoughts
  • feeling sad, hopeless, or irritable most of the time
  • self-doubt
  • lack of interest
  • feelings of guilt
  • pessimism
  • difficulty sleeping
  • low appetite
  • difficulty with concentration
  • memory issues
  • delusional thoughts

Below, we answer some common questions about bipolar disorder.

Does bipolar disorder damage the brain?

Bipolar disorder is associated with structural and functional effects on numerous regions of the brain. When areas of the brain shrink or become altered, it damages their function.

However, it is still unclear whether changes to the brain cause bipolar disorder or occur due to the condition.

Can the brain recover from bipolar disorder?

There is no cure for bipolar disorder, and changes to the brain can be permanent.

However, treatments for bipolar disorder, such as lithium, may have a “normalizing effect” on the brain. The author of a 2015 review concluded that the use of lithium or mood stabilizers is associated with increases in gray matter volume.

Does bipolar disorder worsen with age?

Every person with bipolar disorder is different and may experience different symptoms throughout their life.

Episodes of depression and mania may decrease with age, according to the Depression and Bipolar Support Alliance. It states that mania may decrease more than depression.

However, this is not true for everyone, and mania or depression may increase with age for some individuals.

Can a person ever feel ‘normal’ with bipolar?

Between episodes of depression and mania, a person with bipolar may have periods where they have a regular mood. With effective treatment, the severity and number of episodes a person has may also reduce and allow a person to live as regular a life as possible.

Bipolar disorder is a mood disorder that causes extreme shifts in mood. In the brain, there is an association with bipolar disorder and several structural and functional changes.

Affected areas of the brain include the hippocampus, prefrontal cortex, gray matter, and neurotransmitters.

Researchers are not sure whether these changes cause or result from bipolar disorder.