Bipolar disorder is a mental health condition with complex causes. The people in the know previously called it “manic depression” due to its characteristic mood shifts from high-energy mania to spells of deep depression.

But what causes it?

If this sounds like you, you’re not alone. Bipolar disorder affects 2.8 percent of adults in the United States.

We looked at the possible causes of bipolar disorder (but spoiler alert: scientists don’t really know what they are yet).

Bipolar disorder is still a bit of a mystery. Experts haven’t pinpointed a single cause. Instead, they think it involves a combination of factors rather than just one. Because obviously it had to be as complicated as possible.

You may have a genetic predisposition to bipolar disorder. However, just because it runs in your family doesn’t mean you’ll also develop it. Your genes don’t appear to be the only culprit.

If you have bipolar disorder, the physical structure of your brain may be different, or the balance of your neurotransmitters (temperamental chemical messengers that they are) may be out of whack.

Researchers are still learning about how a brain with bipolar disorder is different than one without. This will help them develop treatments to help you. At the moment, doctors make a diagnosis based on your symptoms rather than brain imaging.

Find out about the different types of bipolar disorder here.

So, is bipolar disorder genetic?

Although the causes of bipolar disorder are complicated, researchers know it runs in families.

If someone in your family has bipolar, your risk of developing it is 4 to 6 times higher than the risk of someone who has no relatives with the condition.

But genetics alone can’t explain why one person develops bipolar and another doesn’t. Many genetic factors contribute to this hereditary link, and there isn’t a single gene that can cause bipolar disorder by itself.

Researchers have looked at identical twins to work out what’s going on. So far, it seems that if one twin has bipolar disorder, there’s around a 70 percent likelihood the other twin will also develop bipolar at some point.

This figure is puzzling. It’s around 2 to 3 times the reported rate for nonidentical twins, suggesting a strong genetic link. But if genetics alone were the whole story, then you’d expect bipolar disorder to develop in both twins with 100 percent certainty.

Last time we checked, 70 isn’t 100. It’s simply not the case that all identical twins will share bipolar disorder. Instead, it shows that other factors are at play, including your biology, emotional state, and the world around you.

Ugh, bipolar disorder! Make more sense!

If you have a relative with bipolar disorder, ask your doctor if screening is a wise precaution. But remember: if someone in your family has bipolar disorder, it doesn’t mean you will too.

Conversely, having bipolar disorder doesn’t mean you have a family history of the condition.

Your brain uses a smorgasbord of chemicals to communicate with other parts of your brain. These chemical messengers, or neurotransmitters, are critical to your brain and body’s functions.

Doctors think that faulty brain circuitry can cause bipolar disorder.

The primary neurotransmitters that researchers associate with the how mood disorders like bipolar develop in your body are noradrenaline and serotonin, or the happiness hormone.

If there’s an imbalance in the levels of one or more of these chemicals, you could develop bipolar disorder symptoms.

For example, there’s evidence that mania episodes may occur when levels of noradrenaline are too high, and episodes of depression may result from levels becoming too low.

Dopamine regulates circuits in the part of the brain that controls pleasure and emotional reward — in other words, the feeling that everything is well and you’re on the right track. Mental health conditions like psychosis and schizophrenia have links to disruptions in these circuits.

Serotonin plays an essential role in mood, sleep, appetite, and memory. If the brain circuits that use serotonin as a chemical messenger malfunction, this can contribute to mood disorders like depression and bipolar disorder.

A delicate balance of these chemicals keeps your brain ticking over as it should. There’s a tiny margin of error. If an environmental or biological trigger destabilizes the neurotransmitter levels, you could develop bipolar symptoms.

Research shows that bipolar disorder can affect the grey matter in your brain. Grey matter helps you control impulses, process information, and regulate your motor skills.

If you have reduced grey matter, you may also have less control over your impulses and emotions. This finding could explain the impulsive and risky behaviors that sometimes accompany a manic episode.

When you feel sluggish and blue during a depressive bipolar episode, this could also be because of reduced grey matter levels.

Bipolar disorder can also affect your brain’s hippocampus, which processes long-term memories and affects how you respond emotionally to situations.

The hippocampus may be smaller in people with bipolar disorder compared to those with no mental health issues. If the hippocampus shrinks, it can lead to depression, irritability, and memory problems that contribute to paranoia.

Factors other than your own genetic and chemical makeup could affect your mental health. You may think the mood episodes central to bipolar disorder are random and uncontrollable.

Still, in reality, there’s a range of experiences and external factors that may trigger a switch of moods or worsen any symptoms you’re already having. Saying that, many episodes happen without an obvious trigger.

Possible triggers include:

Hormones

Hormones seem to play a role in bipolar disorder, but experts disagree precisely how. It could be that hormone imbalances trigger bipolar episodes or that fluctuating hormones cause mood swings that resemble bipolar symptoms.

It’s what the docs call a diagnostic conundrum.

Stress

If bipolar disorder runs in your family, you may find that stressful life events can act as a trigger. These events don’t necessarily have to be traumatic, but drastic or sudden life changes can have effects whatever shape they take.

For example, good stuff like getting married or starting that fantastic new job can feel equally stressful to your brain as bad stuff like losing someone you love.

Substance misuse

Substance misuse doesn’t cause bipolar disorder in isolation. Saying that, if you use drugs and alcohol, they can trigger an episode or make symptoms worse.

Recreational drugs like cocaine, ecstasy, and amphetamines can bring on mania, while booze and tranquilizers could trigger depression.

Medication

If a doctor prescribes you medications like antidepressants, it could trigger a manic episode.

If you’re prone to the effects of bipolar disorder, over-the-counter (OTC) cold medication, caffeine, thyroid medication, and corticosteroids may also trigger symptoms.

Always be open with your doctor about a diagnosis of bipolar disorder.

Seasonal changes

You may find that episodes of mania and depression change with the seasons. Summertime may trigger manic episodes, whereas fall, winter, and spring bring on bouts of depression.

Sleep deprivation

Regular shuteye is essential for your body and mind. Not having a consistent sleep schedule or even just skipping a few hours of rest may trigger mania.

By understanding and identifying what triggers your bipolar episodes, you can discover coping strategies for protecting your mental health.

The causes of bipolar disorder are complex and don’t depend on one specific factor. Even if you have someone in your close family with the condition, it doesn’t mean you’ll develop it too.

If you’re already vulnerable to bipolar, a range of external factors can trigger a depressive or manic episode or make your current symptoms worse.

The good news is that with diagnosis, treatment, and management, you can still live a happy and fulfilling life if you have bipolar disorder.

If you’ve got someone in your family with bipolar and want to arrange a screening, or if you’re having symptoms yourself, seek consultation with your doc or mental health provider to plan the next steps.