Crow T J
Br J Psychiatry. 1986 Oct;149:419-29. doi: 10.1192/bjp.149.4.419.
Three observations challenge Kraepelin's binary view of the functional psychoses: a bimodal distribution of the clinical features of manic-depressive illness and schizophrenia has not been demonstrated; affective illness appears to predispose to schizophrenia in later generations; and 'schizoaffective' illnesses cannot be separated in family studies from either of the prototypical psychoses. The alternative concept is that psychosis is a continuum extending from unipolar, through bipolar affective illness and schizoaffective psychosis, to typical schizophrenia, with increasing degrees of defect. According to this concept the genes predisposing to psychosis have a degree of stability that ensures that the form of the psychosis tends to remain the same within families, but there is also the possibility of change, implying that the genetic mechanisms themselves are variable. It is proposed that quantal changes in the 'virogene' are due to replications within the genome (e.g. the generation of tandem repeats of the element or a component of it); that such replications occur at a critical stage (e.g. gametogenesis, fertilisation, very early embryogenesis) in the course of reproduction; and that the 'season of birth effect' reflects the operation of the mechanism responsible for these replications.
躁郁症和精神分裂症的临床特征并未呈现双峰分布；情感性疾病似乎会使后代更易患精神分裂症；在家族研究中，“分裂情感性”疾病无法与任何一种典型精神病区分开来。另一种观点认为，精神病是一个连续体，从单相障碍开始，经过双相情感性疾病和分裂情感性精神病，延伸至典型的精神分裂症，缺陷程度逐渐增加。根据这一观点，易患精神病的基因具有一定程度的稳定性，这确保了精神病的形式在家族内部倾向于保持不变，但也存在变化的可能性，这意味着遗传机制本身是可变的。有人提出，“病毒基因”中的量子变化是由于基因组内的复制（例如该元件或其一个组成部分的串联重复序列的产生）；这种复制发生在生殖过程中的关键阶段（例如配子发生、受精、早期胚胎发育）；并且“出生季节效应”反映了负责这些复制的机制的作用。
