If someone in your family has had it your 60-80 more likely to have it because its main cause is genes. 

Other reasons include long term stress or abuse when you were young. 

Why is this an issue if you have bipolar you have manic and depressive phases.

You can change phases sometimes they last for a week and sometimes months or even years.

Bipolar disorder can often be mis diagnosed as severe depression on severe ADHD.

If you’re in a manic phase you don’t sleep as much, and you take risks you wouldn’t usually take. Also, may be irresponsible with money normally last over a week however if not treated can last half a year.

If your depressed phase, you may have low energy sleep a lot or not enough. You may not want to do anything and may have suicidal urges depending on how severe the bipolar is.

It is believed that 60-80%  of the risk is involved with genetics.

42% of identical twins have it and 11% of fraternal twins. 

30-50% of adults with bipolar say they have had traumatic experience or abuse in their child hood.

Most people are diagnosed 5-10 year after first having symptoms.

Even though genetics have the biggest role environment and experiences do as well.

So, we could find out what genes cause bipolar and genetically modify humans to make it less likely. However, that may have negative effects in different ways.
 also most wouldn’t approve. 

A less effective but easier solution would be to find ways to make children’s life’s less stressful which is still difficult. 

The first one would be more effective but cause more outrage and have more potential consequences.