Bipolar 1 disorder is a mental health condition characterized by periods of manic episodes and depressive episodes. According to the National Institute of Mental Health, having certain genes may increase your risk of developing bipolar 1 disorder. This means there is a risk of inheriting the condition from a close relative or passing it down to your offspring.
Learning how bipolar 1 disorder is inherited and the genetic risk factors associated with it can help you better understand the disorder. It’s also important to note that just because you or a family member may be at an increased risk for a condition doesn’t mean you will develop it.
In the early 2000s, doctors and researchers began looking deeper into the genetic code found in our DNA. As of April 2022, they’ve entirely sequenced the human genome, made up of more than 3 billion letters (known as base pairs) that code for proteins and other components of our cells.
Researchers use this as a reference to look for changes in certain genes that can lead to diseases. Identifying the genetic mutations associated with specific diseases also makes it possible to prescribe treatments that are more likely to work. This is known as personalized medicine, and it’s become a popular way of treating many conditions.
To learn more about how gene changes contribute to certain diseases, researchers use a genome-wide association study. They take blood samples or cheek swabs from people who have a particular disease and from those without it. DNA is purified from the sample, then placed into a machine to look for gene changes — this is known as sequencing.
Specifically, researchers are looking for single-letter changes in the billions of bases, which may affect how a protein functions in a person’s cells. Known as single nucleotide polymorphisms (SNPs), these variants may seem small, but they can have a big impact on your health.
If these single-letter changes are more common in people with a specific disease, then they’re said to be “associated” with it. These large-scale genetic studies help researchers learn more about which parts of the genome may be causing diseases.
Neuroscience researchers are still learning about the exact cause of bipolar disorder, but they believe it’s a combination of genetic components and environmental factors. Overall, research shows that the cause of bipolar disorder is 60 percent to 80 percent due to genetic factors.
Family studies are an important part of genetics because they help researchers better understand how genes are passed down from parents to their kids. If you have a family history of bipolar disorder, you’re more likely to develop it yourself. For example, having a first-degree relative (parent or sibling) with the condition makes you 10 times as likely to develop it.
Researchers have found that bipolar disorder occurs in 5 percent to 10 percent of siblings. Twin studies have similarly shown that if one fraternal (nonidentical) twin has this mood disorder, there’s a 10 percent chance the other twin has it. In identical twins, this chance increases up to 50 percent.
For many mental disorders, there is no single gene that causes them. Instead, they’re often caused by changes in many genes that affect different pathways in the brain.
In 2021, doctors and researchers conducted a large genetics study of bipolar disorder to look for specific genes involved in the disease. A genome-wide association study included DNA from around 413,000 people — nearly 42,000 of whom had bipolar disorder.
Overall, the study found that 64 loci (regions) of the human genome are associated with an increased risk of bipolar disorder. Many of these genes found in these regions are expressed in the brain by neurons, cells that send messages to each other. Cells that express these genes are found in regions of the brain that control learning, memory, social behavior, and decision-making.
Since many of the genes involved in psychiatric disorders overlap, researchers also investigated how similar bipolar disorder is to other disorders. They found that schizophrenia and bipolar 1 disorder are genetically similar, which may help doctors learn more about diagnosis and treatment. Schizophrenia also shares some symptoms of bipolar disorder, including psychosis which is a state of disconnection from reality.
Since there are several genes now associated with bipolar 1 disorder, some doctors may eventually use a personalized medicine approach to treating it. In the future, you may have your DNA sequenced to look for certain genes that can be targeted with specific medications.
The 2021 study showed some genes associated with bipolar disorder suggest the possibility of targeted treatments. For example, calcium channels — which play a role in the cardiovascular system by controlling blood pressure — may be involved in bipolar 1 disorder. This means that there may be potential for treating the mood disorder with calcium channel blockers, which are already approved by the U.S. Food and Drug Administration (FDA) for treating high blood pressure. The study also revealed genes associated with bipolar disorder that code for targets of antipsychotics (used to treat psychosis in bipolar 1 disorder), anti-seizure medications, and anesthetics.
Another study published in 2022 found that changes in a gene called AKAP11 are associated with an increased risk of bipolar disorder. The study also found that AKAP11 gene variants may interact with the antipsychotic drug lithium, helping researchers learn more about how this treatment works.
Even though genetics can play a big role in causing bipolar 1 disorder, other factors can be responsible. For example, studies have found environmental factors contribute to an increased risk of developing this mood disorder. Traumatic or stressful life events, such as emotional neglect or abuse as a kid, are associated with bipolar 1 disorder.
The risk of bipolar 1 disorder also increases if you’ve recently been married, gone through a divorce, given birth, or lost a close family member to suicide. Misusing alcohol and use of illicit drugs are also linked to bipolar 1 disorder. Genetics may also increase your chances of developing these habits.
If you’re interested in learning more about how bipolar 1 disorder is inherited, or if you have concerns about passing it to your kids, talk to your doctor or a psychiatry professional. They can help you and your family members find answers to your questions and better understand the genetics of bipolar 1 disorder.
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