Refined examinations of bipolar phenomenology appear to be reaching their limit of clinical utility. Despite a plethora of phenomenological studies, the predictive power of symptomatology appears frustratingly inadequate in discriminating, in a more definitive manner, between unipolar and bipolar diatheses. Whether focused on the qualitative distinctions between unipolar and bipolar depressive symptoms or looking for the presence of subthreshold hypomanic symptoms as in the present study, no symptoms, symptom clusters, or individual patient factors have enabled us to accurately identify which patients are most likely to convert. Instead, bipolar disorder continues to reveal itself as increasingly heterogeneous: beyond our current DSM-IV classifications of manias, depressions, and mixed states, clinicians and researchers observe mixed depressions, mixed hypomanias, cyclic irritability, spectrum illnesses, and highly recurrent major depressions. Other definitions of bipolar phenomenology also appear increasingly arbitrary, as rapid cycling appears more as a continuum of cycling rather than as a discrete cut point of four episodes or more per year (9). And, while there is hope that biomarkers may one day aid in more accurate diagnosis or prognosis, we have yet to find neurobiological markers pathognomonic of the disease.