This link that takes you to a synopsis of DSM 4 criteria for bipolar disorder: Nami.org
This is too narrow a definition. "Bipolarish" or "Bipolar Light" may eventually come to be recognized as a very common mood disorder. Perhaps as common as garden variety depression. Treated correctly with Mood Stabilizers instead of with Antidepressants, the results can be impressive.
My prediction is that unstable moods with activated states and qualities will someday be the heart of the new paradigm. Time frames and exactly how many of this or that specific symptom will fade in importance with time, just as it has for depression, anxiety and other syndromes. Two key questions to look at, "Is it a persistent depressed mood or trouble regulating mood shifts that is the main problem?" and "Are there energized atypical behavior periods with decreased need for sleep?".
Most people think that "Mania" is what people complain about in Bipolar Disorder. It's not. Hypomania may not only not bother the patient. In fact, they make like how it feels. Depressions are what bother most bipolars.
It reminds one of former New York Mayor Ed Koch's joke: "I don't get ulcers, I give them".
Some researchers conceptualize borderline personality disorder as part of the bipolar spectrum. Connected with this construct is that bipolarish problems lead to dysfunctional intimate relationships, just like they do in borderline personality. Perhaps this is true because the bipolar's mood state may be irritable and touchy more often than "up" or elated. To better understand this controversy, "Is it Borderline Personality or is it Bipolar?", the following Buddhist parable is shared.
Several blind men are set upon an elephant and told to describe it. Each grabs a different part, one the head, one the leg, one the trunk, etc. Then they each describe the elephant as different things ranging from a basket to a pillar depending on what part of the elephant the blind men feel. Soon they start arguing amongst each other as to who is right. As all the men are blind, they can not see that they are all describing pieces of a single cohesive entity.
I was reminded of this Buddhist tale when having dinner with two esteemed psychaitrists. Both worked in corrections. One described a population rife with personality disorders, but few bipolars. To to the other, their patients were mostly previously undiagnosed bipolars, with a few personality disorders. As they debated each other back and forth, I couln't help but wonder silently to myself : "What are the odds?"
Just my two cents on a controversial area...time will tell.