A third alternative, as noted by Jaspers [43], and more recently suggested by Maj, is that psychopathology may indeed be “intrinsically heterogeneous”, with “ ‘true diseases’ (such as general paresis), which have clear boundaries among themselves and with normality; ‘circles’ (such as manic-depressive insanity and schizophrenia), which have clear boundaries with normality but not among themselves; and ‘types’ (such as neuroses and abnormal personalities), which do not have clear boundaries either among themselves or with normality” [44]. Indeed, results from the current study support such an interpretation as well in that bipolar disorder only appears to intersect with extremes of internalizing and externalizing psychopathology (i.e., the multimorbid class). Future research is doubtless required to understand what the true nature of psychopathology may be [45].
