It used to be called Manic Depression. Its a mental disorder characterized by periods of different moods and depression
Bipolar Disorder is a neurobiological disorder and severely affects 5.5 million people by the age of 18.
You can tell if someone has it if they have low energy, lack of concentration or if their irritable.
There are many ways to deal with depression like getting help from a professional or a loved one. Educate yourself. Learn all you can about what your going through, by knowing all you can then this can help you make clearer decisions on how to get help. Have hope, you must believe you can cope with this disorder before you can actually get help because if you don't believe that you will get through it then all the time your putting into it will be useless. And most importantly, have lots and lots of support.
There are many things and people that can help you. There's clinical support, books, websites, and support groups.