what causes it and why does it affect the people around us?

How are a) Bipolar Disorder, and b) Premenstrual Syndrome diagnosed? Are these things determined through, say, readings of brainwave frequencies, blood tests, just plain old therapy…? Is it common to misdiagnose these conditions?
Thanks

I have stomach cramping, nausea for about a week 1/2, headaches, anxiety, and I think my tummy is a little bloated, different bowel movements, I have not gotten my first period yet, but I have under arm hair, and some down there, and my breasts are a little sore, is this PMS?
I just put back [...]

DRUGS in the Selective Serotonin Reuptake Inhibitor (SSRI) group are typically used for the treatment of depression and general anxiety disorders. However, it has been seen that they are also very effective in the treatment of premenstrual syndrome (PMS) and premenstrual dysphoric disorder (PMDD) in women.
What is PMS and PMDD:
The hormone-producing endocrine system causes [...]

There are so many symptoms that can fall under multiple health conditions. This makes it imperative for you if have any new symptoms of any kind or old ones that won’t go away for you to consult with your doctor to rule things out and hopefully identify and treat your symptoms appropriately. Premenstrual Syndrome [...]

Are you tired of those days of the months where you can not zip up your jeans without having to lay down on the bed, breathing in, or jumping up and down to get into one leg? Then you get irritable to top it off? You are not alone. Ninety percent of all women suffer [...]