Some people may have a genetic risk of developing bipolar disorder. Specific brain changes and environmental factors may trigger the disorder.

Bipolar disorder causes changes in a person’s mood and energy. These extreme and intense emotional states, or mood episodes, can affect their ability to function. People with bipolar disorder can have periods of normal moods as well.

Mood episodes are categorized into:

  • manic
  • hypomanic
  • depressive

These mood episodes are marked by a distinct change in behavior.

During a manic episode, someone can feel extremely energetic or irritable. Hypomania is less severe than mania and lasts for a shorter period of time. A major depressive episode can cause feelings of intense sadness or fatigue.

The new edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) lists more than four types of bipolar disorder. The three most common types are:

  • Bipolar I disorder. Manic episodes last at least seven days at a time. Symptoms can be so intense a person may need hospitalization. Depressive episodes that last at least two weeks may also occur.
  • Bipolar II disorder. This type has a pattern of depressive and hypomanic episodes without any intense manic episodes. It may be misdiagnosed as depression.
  • Cyclothymic disorder. This is a milder form of bipolar disorder. It involves alternating episodes of hypomania and depression. It lasts at least two years in adults and one year in children and adolescents.

Your doctor may diagnose you with another type of bipolar disorder, such as:

  • substance induced
  • medical related
  • unspecified bipolar disorder

These types may share similar symptoms, but they have different episode lengths.

No single factor seems to be responsible for the development of bipolar disorder. Researchers are continuing to try and determine the causes so that more effective treatments can be developed.

Research in genetics and bipolar disorder is fairly new. However, more than two-thirds of people with bipolar disorder have a relative with either bipolar or major depression. Researchers are still trying to find genetic factors responsible for increased risk.

Inherited risk

Someone with a parent or sibling with bipolar disorder has a 4 to 6 times higher risk of developing it as compared to someone who doesn’t.

The American Academy of Child & Adolescent Psychiatry reports that an identical twin has a 70 percent chance of being diagnosed with bipolar disorder if their twin has it .

A 2016 review of twin studies found that there’s a heritable component to bipolar disorder. The review noted that the brain structure of a twin with bipolar disorder differs from the twin without bipolar disorder.

Bipolar and schizophrenia overlap

Researchers who study families and twins suggest that there may be a genetic link between bipolar disorder and schizophrenia. They also found that small mutations in specific genes appear to affect bipolar risk.

ADHD overlap

A 2017 study found a genetic correlation between early-onset bipolar disorder and ADHD. Early-onset bipolar disorder occurs prior to age 21.

Scientists are working to discover how the brains of people with bipolar disorder differ from the brains of people without it. Here are some interesting perspectives.

Brain cells

The loss or damage of brain cells in the hippocampus can contribute to mood disorders. The hippocampus is the part of the brain associated with memory. It also indirectly affects mood and impulses.


Neurotransmitters are chemicals that help brain cells communicate and regulate mood. Imbalances with neurotransmitters may be linked to bipolar disorder.

Mitochondrial problems

Research suggests that mitochondrial problems may play a role in mental disorders, including bipolar disorder.

Mitochondria are the energy centers in almost every human cell. If the mitochondrion doesn’t function normally, it could lead to change in patterns of energy production and use. This may explain some of the behaviors we see in people with psychiatric disorders.

Researchers who performed MRIs on the brains of people with bipolar disorder in 2015 found elevated signals in certain parts of the brain. These parts help coordinate voluntary movement, suggesting abnormal cellular function.

Some scientists believe that environmental and lifestyle factors play a role in bipolar disorder. These factors include:

  • extreme stress
  • physical or sexual abuse
  • substance abuse
  • death of a family member or loved one
  • physical illness
  • ongoing concerns that affect your daily life, such as money or work problems

These situations can trigger symptoms or affect the development of bipolar disorder, especially for people who may already be at a high genetic risk.

Bipolar disorder affects about 2.8 percent of the U.S. adult population. It equally affects genders, races, and social classes.

Age risk

Bipolar disorder usually develops around age 25, or between the ages of 15 and 25. At least half of all cases are diagnosed before the age of 25. However, some people do not develop symptoms until they are in their 30s or 40s.

While it’s possible for bipolar disorder to develop in children age 6 or younger, the topic is controversial. What may seem like bipolar disorder can be a result of other disorders or traumas.

Gender risk

Bipolar II disorder is more common in women than in men. But bipolar I disorder is equally prevalent in both sexes. It’s not known exactly what causes this difference in diagnoses.

Hormonal risk

Experts believe that thyroid hormones have major effects on brain function in adults. Depression and bipolar disorder are associated with abnormal thyroid function.

The thyroid is a gland in the neck that releases hormones regulating growth and development. People with bipolar disorder often have hypothyroidism, or an underactive thyroid.

Certain factors can trigger manic or depressive episodes. These factors increase the body’s stress level, which is also a trigger. Being familiar with your own personal triggers is one way to keep symptoms from worsening.

While triggers vary from person to person, some common ones include:

  • stressful life events, which can be positive or negative, such as the birth of a baby, a job promotion, moving to a new house, or the end of a relationship
  • disruption in regular sleep patterns, including decreased or increased sleep or bed rest
  • change in routine, like in sleep, eating, exercise, or social activities (structured routine can lower stress)
  • too much stimulation, like specific or loud sounds, too much activity, and caffeine or nicotine consumption
  • alcohol or substance abuse; overuse can cause ongoing bipolar symptoms, relapses, and hospitalizations
  • unmanaged or untreated illness

With proper diagnosis, treatment, and management, it’s possible to lead a fulfilling, happy life with bipolar disorder.

Schedule an appointment with your doctor if you feel you have one or more of the signs of bipolar disorder. They can check your physical health and also ask you some mental health screening questions.

If your doctor doesn’t find a physical problem for your symptoms, they may recommend that you see a mental health provider.

Your treatment will depend on your condition. It can vary from medication to therapy. Finding the right treatment can take some time. Talk to your doctor if any medication causes unwanted side effects. There are other options you can try.