What Causes Bipolar Disorder?

Researchers studying bipolar disorder over the past decades have several theories to explain how this condition develops. Existing evidence points to a range of possible causes rather than one specific cause.

Experts believe bipolar disorder usually develops from a combination of the following factors:

• genetics
• brain chemistry and biology
• environmental factors

If you’re noticing symptoms for the first time, you might link them to a recent source of stress, a health issue, or a new medication.

These things can absolutely trigger mood episodes, but they don’t directly cause bipolar disorder.

Bipolar disorder tends to run in families.

According to the recent edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), if you have an adult relative with either bipolar I or bipolar II disorder, you have an average of 10 times the chance of developing the condition yourself.

The American Psychiatric Association also reports that 80 to 90% of people with bipolar disorder have a relative living with either depression or bipolar disorder.

Related factors that influence your likelihood of developing bipolar disorder include:

• family history of depression
• family history of schizophrenia (research points to some genetic overlap between these two conditions)
• the number of family members with bipolar disorder or other mood disorders
• your relation to those family members

Generally speaking, closer kinship increases this likelihood. For example, someone whose sibling or parent has bipolar disorder has a greater chance of developing the condition than someone whose cousin or uncle has it.

Researchers have linked two key genes, CACNA1 and ANK3, to bipolar disorder. But they note that many other genes are likely to factor in too.

What’s more, since genes make up only one part of the picture, not everyone with a family history of bipolar disorder will develop the condition.

Studies on twins support this. Evidence suggests that when one identical twin has bipolar disorder, the other has a high — but not certain — chance of the same diagnosis.

Bipolar disorder also has a neurological component.

Neurotransmitters are chemical messengers in the brain. They help relay messages between nerve cells throughout the body. These chemicals play an essential role in healthy brain function. Some of them even help regulate mood and behavior.

Older research links three main neurotransmitters to bipolar disorder:

• serotonin
• dopamine
• norepinephrine (also called noradrenaline)

Imbalances of these brain chemicals may prompt manic, depressive, or hypomanic mood episodes. This is particularly the case when environmental triggers or other factors come into play.

The role of mitochondria

Experts also believe mitochondria — which you may remember from science class as the cells that generate energy, aka “the powerhouse of the cell” — may have something to do with the development of mood disorders.

When cells don’t produce or metabolize energy as they typically would, the resulting imbalances in brain energy could lead to the changes in mood and behavior often seen with bipolar disorder.

Brain structure and gray matter

Some evidence suggests people with bipolar disorder have less gray matter in certain parts of the brain, including the temporal and frontal lobes.

These brain areas help regulate emotions and control inhibitions. A lower volume of gray matter may help explain why emotion regulation and impulse control become difficult during mood episodes.

Gray matter contains cells that help process signals and sensory information.

Research has also linked the hippocampus, a part of the brain implicated for learning, memory, mood, and impulse control, to mood disorders. If you have bipolar disorder, your hippocampus may have a lower total volume or a slightly altered shape.

These brain differences may not necessarily cause bipolar disorder though. Still, they offer insight on how the condition might progress and affect brain function.

Family history can certainly increase the likelihood of developing bipolar disorder, but many people with a genetic risk never develop the condition.

Various factors from your surrounding environment offer another point of connection to consider. These might include:

• personal experiences
• health and sleep
• external stress triggers
• alcohol or substance use

Research shows that childhood trauma is a risk factor for bipolar disorder, and is associated with more severe symptoms.

This is because strong emotional distress in childhood might affect your ability to regulate your emotions as an adult. Childhood trauma can include:

• sexual or physical abuse
• neglect
• traumatic events
• extreme living situations

It’s important to draw a distinction between bipolar disorder causes, such as genetics and brain chemistry, and triggers. They interact to produce mood episodes, but they aren’t entirely the same thing.

You could begin experiencing mood episodes after certain life events, like a rough breakup, job loss, or childbirth. Certain habits, like not getting enough sleep on a regular basis or drinking a lot of alcohol, can also trigger mood episodes or make them more severe.

None of this means you’re to blame, though. No one can conclusively say who will and won’t develop bipolar disorder. Its causes lie beyond your control.

Other possible environmental factors might include:

• underlying health conditions
• diet
• sudden, severe stress, such as a death or other loss
• persistent, smaller-scale stress, such as trouble at work or family problems

Between mood episodes, you might not notice any symptoms of bipolar disorder. Still, it’s fairly common to have other conditions along with bipolar disorder.

Conditions that often occur with bipolar disorder include:

• Anxiety. Research suggests at least half of all people with bipolar disorder will likely experience an anxiety disorder at some point in life.
• Post-traumatic stress disorder (PTSD). Bipolar disorder has been linked to childhood trauma, so it’s understandable that many people are dealing with PTSD too.
• Attention deficit hyperactivity disorder (ADHD). Bipolar disorder often occurs with ADHD, especially when mood symptoms begin before the age of 21.
• Substance use disorders. The DSM-5 notes more than half of all people who meet the criteria for a bipolar disorder diagnosis also have an alcohol use disorder or other substance use disorder.
• Psychosis. Delusions, hallucinations, and other symptoms of psychosis are often symptoms of schizophrenia, but they can also happen with bipolar disorder.
• Eating disorders. Many people living with bipolar disorder also have an eating disorder. Bulimia nervosa and bipolar II disorder appear most strongly linked.
• Migraine. Research suggests people with bipolar disorder have a much higher risk for migraine.

Treating bipolar disorder with medication can be something of a delicate balance. Antidepressants that help ease depressive episodes can sometimes trigger manic episodes.

If your healthcare provider recommends medication, they might prescribe an antimanic medication such as lithium along with an antidepressant. These medications can help prevent a manic episode.

As you work to develop a treatment plan with your care provider, let them know about any medications you take. Some medications can make both depressive and manic episodes more severe.

Also tell your care provider about any substance use, including alcohol and caffeine, since they can sometimes lead to mood episodes.

Some substances, including cocaine, ecstasy, and amphetamines, can produce a high that resembles a manic episode. Medications that might have a similar effect include:

• high doses of appetite suppressants and cold medications
• prednisone and other steroids
• thyroid medication

If you believe you’re experiencing a mood episode or other symptoms of bipolar disorder, it’s always a good idea to connect with your healthcare provider as soon as possible.

Its causes may be complex, but bipolar disorder is very treatable. While you don’t have control over whether you develop the condition, you can take steps to manage mood episodes and other symptoms.

To get started, consider talking with your care provider about a treatment plan that works well for you. Many people find medication helps stabilize mood changes, so a doctor or psychiatrist may recommend medication as a primary treatment.

Therapy and alternative treatments can also have benefit. A therapist can help you address mood symptoms. And therapy in general also provides the opportunity to build healthy coping skills to manage stress and triggers on your terms.

Looking for more treatment info? Get a deep dive on bipolar disorder treatment here.