Causes and Risk Factors of Bipolar Disorder

Bipolar disorder (BPD) is a mental health condition that causes extreme changes in mood and energy levels. These mood swings range from emotional highs (mania or hypomania) to lows (depression). These mood swings may occur rarely or many times a year. The condition is lifelong but can be treated.¹

Doctors believe a combination of genetics and environment lead people to develop BPD. The condition is one of the top 10 leading causes of disability worldwide.^1-3

Biological differences

Studies show that people with BPD have physical differences in their brains compared to people without the condition. Doctors do not yet understand how these changes may affect the development of BPD.¹

Studies seem to suggest that imbalances in the neurotransmitters that control mood lead to bipolar episodes. Neurotransmitters are chemicals that carry messages from one cell to another. These messages tell the body how to work. The neurotransmitters dopamine and serotonin may not work properly in people with BPD.^3,4

Genetics and bipolar disorder

BPD is more common in people who have a first-degree relative with the condition. This means they have a mother, father, sister, or brother with it.³

In 1987, doctors found that a change in chromosome 11 increased the risk of developing BPD. Since that time, at least 30 genes have been linked to a higher risk of the disorder.³

But just because you have a relative with BPD does not mean you will develop it, too. There are many factors to BPD developing.³

Environmental factors

Doctors use the word “epigenetics” to describe environmental factors that change a person’s genetics. For example, what you eat, stressful life events, drug and alcohol use, or exercise can change whether your genes turn on or turn off the way they should. This means that the genes you inherit can be changed after you are born.⁵

A wide variety of things are known to be more common in the environments of people who develop BPD before they are diagnosed. These things also can trigger episodes after a person is diagnosed. They include stressful events and trauma during childhood.³

This is why doctors believe a combination of what is inherited and what is experienced lead some people to develop BPD.³

Stressful events

Many events can create stress over a person’s lifetime. For example, people at risk of developing BPD may develop the condition after experiencing:³

• Childbirth
• Divorce
• Job loss
• Disability
• Loss of a loved one

Studies show that people with BPD report at least 1 stressful event in the 6 months before a new episode of mania or depression. But results are not clear about whether extreme stress during pregnancy is a risk for the child developing BPD.³

Stressful events are different for everyone. Some things that seem simple may act as triggers for someone with BPD. For example, going to college may be a trigger for some.

Childhood trauma and poverty

There is a growing understanding that adverse childhood events (ACEs) can have a lifelong impact on mental and physical health. ACEs are difficult experiences that a person may have growing up. Examples of ACEs include:⁶

• Physical, emotional, or sexual abuse, or neglect
• Witnessing abuse, neglect, or violence
• Living in a home with substance misuse, mental health conditions, or physical disability that prevents quality caregiving
• Low income, job or housing instability, or low education levels
• Lack of social interactions or negative social interactions

Not everyone who lives through ACEs develops bipolar disorder. But childhood trauma is linked to higher rates of BPD and poor response to treatment.^3,6

Other medical conditions

BPD is known to commonly occur in combination with several other health conditions, including:³

• Drug or alcohol misuse
• Irritable bowel syndrome (IBS)
• Asthma
• Obesity
• Migraine
• Multiple sclerosis (MS)
• Other mental health conditions such as anxiety, ADHD, and aggression

Doctors do not yet understand if there are definite links between these conditions. But the conditions occur together more often than usual.³

Other potential causes of bipolar disorder

Many studies have searched for other explanations for why some people develop BPD and others do not. This is a topic that needs more research. Among the things doctors have considered as potential triggers are:^3,7

• A baby’s exposure to certain viruses, the mother smoking, or extreme stress in the mother, before or after birth
• Education levels
• Urban versus rural living
• Race and ethnicity
• Birth order
• Exposure to pollution

So far, some studies suggest these environmental factors may affect who develops BPD. But results of these studies vary widely and do not yet prove a link.⁷