The categorical view of psychosis is most associated with Emil Kraepelin, who created criteria for the medical diagnosis and classification of different forms of psychotic illness.
[2] The concept of psychosis as a spectrum was further developed by psychologists such as Hans Eysenck and Gordon Claridge, who sought to understand unusual variations in thought and behaviour in terms of personality theory.
[3] Meehl et al. 1964 first coined the term 'schizotypy,' and through examination of unusual experiences in the general population and clustering of symptoms in individuals diagnosed with schizophrenia.
[6] Jackson[7] proposed the concept of 'benign schizotypy' in relation to certain classes of religious experience, which he suggested might be regarded as a form of problem-solving and therefore of adaptive value.
[10] Each approach is sometimes used to imply that schizotypy reflects a cognitive or biological vulnerability to psychosis, although this may remain dormant and never express itself, unless triggered by appropriate environmental events or conditions (such as certain doses of drugs or high levels of stress).
'[11] On the second point, Bleuler discusses in a number of places whether peculiarities displayed by the patient before admission to hospital should be regarded as premonitory symptoms of the disease or merely indications of a predisposition to develop it.
'[11] Later advocates of the quasi-dimensional view of schizotypy are Rado[12] and Meehl,[13] according to both of whom schizotypal symptoms merely represent less explicitly expressed manifestations of the underlying disease process which is schizophrenia.
This model is most closely associated with the work of Hans Eysenck, who regarded the person exhibiting the full-blown manifestations of psychosis as simply someone occupying the extreme upper end of his 'psychoticism' dimension.
However, schizophrenia itself is regarded as a breakdown process, quite distinct from the continuously distributed trait of schizotypy, and forming a second, graded continuum, ranging from schizotypal personality disorder to full-blown schizophrenic psychosis.
The fully dimensional approach argues that full blown psychosis is not just high schizotypy, but must involve other factors that make it qualitatively different and pathological.
[21] Low cooperativeness and self-directedness combined with high self-transcendence may result in openness to odd or unusual ideas and behaviours associated with distorted perceptions of reality.
[64] Essentially, this means that schizotypy is a cognitive-perceptual specialization for processing chaotic and noisy data, where patterns and relationships exist but can only be detected if minor inconsistencies are ignored (i.e., focusing on the 'big picture').
"[91] Individuals diagnosed with schizophrenia or schizotypy exhibit “reduced or abolished NP [negative priming], especially in the presence of positive symptomatology, acute psychosis, high severity of symptoms, and/or lack of medication.”[92] The phenomenon of semantic activation without conscious identification (SAWCI) is said to be displayed when a person shows a priming effect from the processing of consciously undetectable words.
Schizotypy symptoms have been related to deficits in executive functions, which entails the psychological processes that supersede habitual inclinations with novel responses and behaviors to fulfill important goals.
[74] That is, participants who score highly on schizotypy tend to fail to ignore a previously preexposed, non-reinforced stimulus as compared to a non-preexposed, novel and potentially important event.
Enhanced performance on verbal fluency has been associated with high levels of positive schizotypy, i.e. increased reports of hallucination-like experiences, delusional ideation, and perceptual aberrations.
[95][96][97][98] Claridge[99] suggested that one consequence of a weakness of inhibitory mechanisms in high schizotypes and schizophrenics might be a relative failure of homeostasis in the central nervous system.
Claridge and co-workers[100][101][102] have found various types of abnormal co-variation between different psychophysiological variables in schizotypes, including between measures of cortical and autonomic arousal.
McCreery and Claridge[103] found evidence of a relative activation of the right cerebral hemisphere as compared with the left in high schizotypes attempting to induce a hallucinatory episode in the laboratory.
McCreery[105][106] has suggested that this could account for the phenomenological similarities between Stage 1 sleep and psychosis, which include hallucinations, delusions, and flattened or inappropriate affect (emotions).
In the clinical field there is also the paradoxical finding of Stevens and Darbyshire,[109] that schizophrenic patients exhibiting the symptom of catatonia can be aroused from their apparent stupor by the administration of sedative rather than stimulant drugs.
[110] Dopamine mediates the conversion of the neural representation of an external stimulus from a neutral bit of information into an attractive or aversive entity, i.e. a salient event.