Bipolar disorder, formerly known as manic depression, is a mental illness characterized by extreme shifts in mood and energy levels. People with bipolar disorder experience distinct “highs” known as manic episodes, and “lows” known as depressive episodes. These mood episodes cause significant changes in behavior and functioning.
A common concern among people with bipolar disorder is whether going through repeated mood episodes over time causes permanent brain damage or cognitive decline. Research shows that multiple episodes may impact the brain, but the evidence is complex. Here is what science tells us so far about the effects of bipolar episodes on the brain.
Manic episodes and the brain
During manic episodes, people with bipolar disorder experience heightened energy, activity, and mood. Mania is characterized by symptoms like:
- Feelings of euphoria, extreme optimism, or irritability
- Racing thoughts and rapid speech
- Decreased need for sleep
- Impulsiveness and risky behavior
- Increased drive to pursue goals
- Difficulty concentrating or easily distracted
Studies using neuroimaging techniques suggest that manic episodes impact the structure and functioning of certain brain regions, such as:
- Prefrontal cortex – involved in planning, decision-making, and emotional regulation. Mania is linked to decreased prefrontal cortex activity.
- Limbic system – manages emotion and motivation. Overactivity seen in the limbic system during mania.
- Basal ganglia – part of reward and habit formation circuits. Excessive stimulation of this area found during mania.
However, it’s unclear if these changes persist after the manic episode resolves. One imaging study found prefrontal cortex abnormalities persisted after recovery from mania, while another study found the changes were reversible.
In addition to affecting brain structure and function, mania may impact cognition in other ways:
- Impaired executive functioning – difficulties with planning, focus, organizing
- Poor memory and attention
- Diminished processing speed
- Difficulty learning and retaining new information
For many people, these cognitive effects seem to resolve once the manic episode ends. But some studies indicate mania can lead to subtle long-term cognitive changes.
Depressive episodes and the brain
During depressive episodes, people with bipolar disorder experience low mood and energy levels. Depression in bipolar disorder involves symptoms like:
- Sadness, emptiness, or hopelessness
- Fatigue and loss of interest in activities
- Changes in appetite and sleep habits
- Difficulty concentrating or making decisions
- Feelings of worthlessness or guilt
- Thoughts of death or suicide
Brain imaging research shows that the brains of people with bipolar disorder function differently than average during depression. Brain changes observed include:
- Prefrontal cortex – decreased activity and impaired functioning
- Hippocampus – smaller volume
- Amygdala – increased size and overactivity
Additionally, depressive episodes are linked to:
- Disruptions in cognitive functioning and information processing
- Impaired working memory and executive function
- Slower processing speed
- Problems with attention and concentration
For some people, these changes may linger even after the depressive symptoms improve. There is also evidence that recurrent depressive episodes contribute to worsening cognitive deficits over time.
Progressive brain changes
While individual manic and depressive episodes may cause temporary brain changes, researchers are still studying whether repeated episodes over a lifetime lead to permanent, progressive brain damage.
Some key findings about progressive changes include:
- Total gray matter volume in the brain decreases with more lifetime bipolar episodes.
- The hippocampus and prefrontal cortex show progressive loss of tissue with repeated episodes.
- Ventricles in the brain appear to enlarge with more episodes over time.
- White matter integrity declines and lesions accrue with more episodes.
These brain changes are associated with declining cognitive functioning, including:
- Worsening processing speed, memory, and executive function
- Problems with attention, learning, and mental flexibility
- Poorer social cognition and emotion recognition
However, other studies have failed to find an association between number of episodes and cognitive decline. So the relationship is complex.
Mood episode severity
Some research indicates that episode severity may play a role in brain changes with bipolar disorder. A few key findings:
- More severe manic episodes are linked to greater loss of gray matter.
- Severe mania correlates with more significant cognitive impairment.
- The number of hospitalizations for mood episodes predicts greater cognitive decline.
Hospitalization usually indicates an extremely severe episode. So episode intensity seems to influence brain effects, with severe episodes likely causing more changes than milder episodes.
Contributing factors
In addition to mood episodes themselves, other factors related to bipolar disorder may drive brain changes, like:
- Medications – Mood stabilizers and antipsychotics may affect brain structure and function.
- Drug and alcohol use – Substance abuse is common with bipolar disorder and can cause brain damage.
- Metabolic changes – Bipolar disorder increases risk of medical issues like thyroid problems, obesity, and diabetes that impact the brain.
- Stress – High stress levels can cause changes in brain structure and functioning.
Disentangling the effects of these additional variables from damage caused by mood episodes themselves remains an area of active research.
Protective factors
While episodes may damage the brain over time, certain factors seem to provide some protection against changes:
- Treatment – Effective long-term treatment to control mood episodes may limit damage.
- Early intervention – Getting diagnosed and treated early in the course of illness appears helpful.
- Cognitive reserve – Having greater premorbid cognitive reserve buffers against decline.
- Resilience – Innate brain plasticity and resilience varies between individuals.
Lifestyle factors like regular exercise, a healthy diet, mental stimulation, stress management, and avoiding substance use may also protect the brain.
Reversibility of changes
An important question is whether mood episode-related brain changes are permanent or reversible. The evidence is mixed:
- Some studies show brain structure and cognitive function improve with sustained treatment after an episode.
- Other studies find brain abnormalities and cognitive deficits persist after recovery.
In general, milder short-term changes seem more reversible, while severe cumulative changes may be permanent. But this area needs more research.
Implications
The potential cognitive and functional consequences of bipolar-related brain changes include:
- Worse quality of life, social impairment, disability
- Difficulties managing money, jobs, education
- Problems performing daily tasks and living independently
- Higher relapse rates
- Poorer treatment response
But many people with bipolar disorder maintain high cognitive functioning despite repeated episodes. And research shows cognitive remediation therapies can improve some types of cognitive deficits.
Conclusion
In summary, evidence suggests repeated bipolar mood episodes may cause progressive brain changes over time. These changes are associated with declining cognitive functioning in areas like memory, executive function, and attention.
However, there are many unanswered questions about the effects of bipolar disorder on the brain:
- What specific brain changes occur and whether they persist or reverse after episodes
- The role of episode severity, medications, and other factors
- Who is at highest risk of brain changes
- Whether treatments can prevent damage
While concerning, research does not show bipolar disorder inevitably causes dementia or severe disability. Many people with bipolar disorder maintain cognitive health and functioning. Living a brain-healthy lifestyle and managing bipolar disorder effectively appears key to minimizing negative impacts on the brain.
