Know somebody that you just cannot get on with? Does their behaviour irritate and confuse you? Are they generally a massive pain in the distal digestive tract? There is always the possibility that they have a personality disorder. If, however, everybody you know seems like this... maybe you do!
My experience of mental health issues is that sufferers generally shroud their problems and quietly find ways of coping, with the help of a few trusted friends and professionals. But fakers proudly cruise around in Bipolar Disorder like it's a 24 Carat gold carriage.