German psychiatrist Emil Kraepelin (1856-1926) was one of the first to make a prominent distinction between dementia praecox (roughly corresponding to schizophrenia) with its “irreversible dementing cortical disturbances” and manic-depressive insanity (roughly corresponding to bipolar disorder, especially with psychosis), from which patients “recover with their personality intact.”^1(p28) Toward the end of his career, Kraepelin acknowledged that “there is an alarmingly large number of cases in which it seems impossible, in spite of the most careful observation, to make a firm diagnosis.”^1(p28) Indeed, most patients with psychotic disorders show complex clinical presentations not conforming to classic descriptions of either disorder. Since Kraepelin’s time, there has been great interest in identifying features that distinguish schizophrenia from bipolar disorder because prognosis and treatment approaches differ between the two. To date, the results have been mixed at best. It appears that these disease categories are not completely distinct, although boundaries between them can occasionally be detected using clinical and biological measures (eg, as described by Kotov et al² and Grozeva et al³).

德国精神科医生埃米尔·克雷佩林（Emil Kraepelin）（1856-1926）率先对痴呆症（大致对应于精神分裂症）和“不可逆性痴呆皮层障碍”和躁狂抑郁症（大致对应于躁郁症，尤其是双相情感障碍）做出明显区分。精神病），患者从中“恢复原状”。^{1 （p28）}在职业生涯快要结束时，克雷佩林承认：“尽管进行了最仔细的观察，但仍然有大量病例似乎无法做出确凿的诊断。” ^{1 （p28）}确实，大多数精神病患者表现出复杂的临床表现，不符合任何一种疾病的经典描述。自从Kraepelin时代以来，人们对确定可将精神分裂症与双相情感障碍区分开的特征引起了极大的兴趣，因为两者之间的预后和治疗方法有所不同。迄今为止，结果充其量是好坏参半。尽管有时可以使用临床和生物学手段（例如，如Kotov等²和Grozeva等^3所述）检测它们之间的界限，但这些疾病的类别似乎并不完全不同。