The exact cause of bipolar disorder is unknown, but it may have to do with a combination of genetic and environmental factors and altered brain chemicals and structures.

People with this disorder have manic episodes, or unusually elevated moods in which they may feel very happy, irritable, or “up,” and in which there is a marked increase in activity level.
There are three main types of bipolar disorder: Bipolar I disorder includes manic episodes that last at least 7 days or manic symptoms so severe that they require immediate hospital care. Depressive episodes are also common. They usually last at least two weeks.
Bipolarity can be measured through FAST, it is a simple instrument, easy to apply and fast (time of 3-6 min.). It was developed for the clinical assessment of the limitations presented by psychiatric patients, especially those with bipolar disorder.
SYMPTOMS:
1. An exaggerated self-esteem.
2. Very high and/or irritable mood.
3. Greater sociability.
4. Increased activity and energy.
5. Racing thinking.
6. Less need for sleep.
7. Increased sexual activity.
The bipolar person will feel very depressed. This leads to anxiety, sadness, pessimism and strong feelings of frustration. In addition, you will have a complete loss of interest in everything, even things that you often wanted to do during the manic phase. Little need for sleep. Poor discernment ability. Little control of temperament. Lack of self-control and reckless behaviors, such as excessive drinking or drug use, increased risky sex, gambling, and spending or giving away a lot of money.
RECOMMENDATIONS:
Although there is no cure for this disorder, medications approved by the Food and Drug Administration can treat the symptoms and make the patient feel better. As well as take it into account and spend more time with the person, speak honestly, do not take their comments or their behavior personally and keep the environment as quiet as possible. Try to encourage this person to go out and do things they really enjoy.

https://medlineplus.gov/spanish/bipolardisorder.html#:~:text=No%20se%20conoce%20la%20causa,del%20cerebro%20y%20su%20ambiente.

https://www.mayoclinic.org/es-es/diseases-conditions/bipolar-disorder/symptoms-causes/syc-20355955