Bipolar disorder, formerly known as manic depression, is a mental health disorder that involves extreme mood swings. It is estimated around 4.4% of adults in the US will experience bipolar disorder in their lifetimes. The average age of onset is 25, but it can also occur in teenagers and children.

Experts don't know exactly what causes bipolar disorder, but research suggests that there is both a genetic component and environmental one that contribute to its development.

"Bipolar disorder is characterized by having a history of depressive episodes but more specifically at least one manic episode," says Jared Heathman, MD, a psychiatrist in Houston, Texas. "Manic symptoms include grandiosity, decreased need for sleep, increased rate of speech, flight of ideas, distractibility, and impulsive behaviors that contribute to social or occupational dysfunction."

A hereditary disease is one that can be passed on through genetic material, like from a parent to one of their children. For some hereditary diseases, like one type of breast cancer, physicians know exactly which gene causes the issue, and therefore, how likely it is to be passed along.

The exact genes related to bipolar disorder aren't known, which makes it difficult to explain the exact mechanisms of how the condition is passed on genetically. The leading theory is that several different genes contribute to bipolar disorder, each in a small way.

"Bipolar disorder works on something called a diathesis-stress model, meaning that someone inherits a greater likelihood of the disorder, but some sort of severe physical or mental stress can activate that tendency," says Aimee Daramus, PsyD, a licensed clinical psychologist and author of Understanding Bipolar Disorder: The Essential Family Guide.

According to a Journal of Psychiatry & Neuroscience study published in 2012, people who have one first-degree relative like a parent or sibling with bipolar disorder have a 15% to 35% greater chance of also developing the condition. If someone has two first-degree relatives with bipolar disorder, their chances of having the disorder increase to 75%.

Heathman says people with bipolar disorder have around a 10% chance of having children with the disorder, too. According to him, "most cases" of the condition happen in families where a relative already has bipolar but not all of them.

For bipolar disorder, genetics is just one part of the equation, and needs to be considered alongside other risk factors.

There are environmental and behavioral factors that might increase your risk of developing bipolar disorder. These include:

The relationship between alcohol use or drug use and bipolar disorder isn't fully understood. However, studies found that substance abuse and bipolar disorder can interact with each other to make symptoms significantly worse. A 2004 study published in the journal Bipolar Disorders evaluated 4,310 people receiving treatment for bipolar disorder at Veterans Administration (VA) facilities. Researchers found that 25% of these patients had alcohol use disorder, 10.4% abused cocaine, and 4.4% abused opiates.

"Some drugs are connected with a greater likelihood of developing bipolar if the genetic likelihood is there," Daramus says. For example, Daramus says, "Habitual cannabis use before someone's first mood episode is connected to an earlier age of onset."

A 2008 review published in Dialogues in Clinical Neuroscience looked at various studies about brain imaging in individuals with bipolar disorder and found there may be structural differences in the brain of those with bipolar disorder.

Specifically, a 2017 study published in Molecular Psychiatry found differences in the hippocampus, a part of the brain associated with memory and learning. People with bipolar disorder had abnormal shapes and less volume in that area.

Many conditions are comorbid with bipolar disorder, like depression, anxiety, and PTSD. A 2018 paper published in the American Journal of Psychiatry looked at 6,788 people who experienced substance-induced psychosis a condition where alcohol or drugs induce delusions or hallucinations and found that 32.2% developed bipolar disorder or schizophrenia.

The exact relationship between bipolar disorder and these other illnesses isn't fully understood, but people who suffer from them should also know how to recognize bipolar symptoms, and seek treatment if they appear.

According to a 2016 paper in the International Journal of Bipolar Disorders, experiencing trauma in childhood is connected with a higher risk of developing bipolar disorder. This may include:

Survivors of childhood trauma can have more severe cases of bipolar than people who didn't have those experiences. The researchers aren't certain of what causes the link, but suggest that childhood trauma can affect the way people respond to stressors as adults.

If you have a parent or a family member with bipolar disorder and are worried you may develop the same condition, Heathman says there's no known way to prevent it. But, you can learn how to manage the symptoms. "

A healthy lifestyle that includes a healthy diet and regular, adequate sleep can reduce the frequency of bipolar events," Heathman says.

People with a family history of bipolar disorder should also know the common symptoms, and how to seek professional help if they see signs of behavior that could be related to bipolar disorder.

Much more research is necessary to pin down the exact causes of bipolar disorder, including any specific genetic links and how hereditary the condition is. While bipolar can be a difficult condition to live with, many people do extremely well with medication and/or therapy, under the supervision of a physician.

Read more here:
Is bipolar disorder genetic? Yes, but that doesn't guarantee you'll develop it - Insider - INSIDER