Why don't preschizophrenic children have delusions and hallucinations?

Early and late environmental risk factors for schizophrenia

Although a high proportion of liability to schizophrenia is under genetic control, a number of environmental risk factors have been identified. The earliest of these are complications of pregnancy and birth, though whether these cause or reflect disturbed brain development is not absolutely clear. Neurodevelopmental deviance is also indicated by neurological dysfunction, social, behavioural and cognitive deficits during childhood. Immigrant status is a significant risk factor, especially prominent among the African Caribbean population in England, though the mechanism is unknown. Later environmental risk factors include adverse life events and substance abuse. An additive model of multiple genetic and environmental risk factors of small effect may be too simplistic and an interactive model where genetic predisposition is compounded by environmental effects is more in keeping with current evidence. The nature of such interactions can be explored more fully when susceptibility genes for schizophrenia are identified.

Developmental insanity or dementia praecox: was the wrong concept adopted?

Over a century ago, the Scottish psychiatrist Thomas Clouston proposed the idea of a developmental or adolescent insanity. He characterised the condition as having a male predominance and a poor outcome, and noted the frequency of a family history and of minor anomalies of the palate; he considered it a disorder of cortical development and the onset of psychotic symptoms due to maturation during adolescence "of certain parts of the brain which had lain dormant before". Clouston's idea was subsequently eclipsed by the broader dementia-praecox espoused by Kraepelin and Bleuler, but recent epidemiological, neuroimaging, and neuropathological research supports the existence, within the schizophrenia syndrome of a group of patients with a severe, early onset, developmental psychosis. This disorder, re-christened as neurodevelopmental schizophrenia, is associated with childhood language and speech difficulties which render subjects more likely to later misinterpret their own inner speech as external voices; like all developmental disorders of language, it is commoner in males. Predisposing factors include the inheritance of abnormal cerebral asymmetry, and early environmental hazards of brain development such as prenatal exposure to maternal viral infection and perinatal complications.

Hippocampal synaptic plasticity as a biological substrate underlying episodic psychosis

Structural change in the hippocampal formation has become popular as a proposed neurobiological substrate for schizophrenic disorders. It is postulated that behavioral plasticity in the form of long-term potentiation of hippocampal synaptic transmission is an attractive putative mechanism for the mediation of transient psychosis. Moreover, the disturbed hippocampal neuroarchitecture found in schizophrenic brain may be susceptible to potentiation and dysfunctional to the degree that delusions and hallucinations develop. Partial and selective blockade of the receptors mediating potentiation may prove to be an efficient means of preventing psychotic episodes and avoiding further damage to the involved network. Basic research, utilizing experimental models such as intraventricular kainic acid injection, may help to clarify the anatomical and physiological substrate of psychosis.

An integrative psychophysiological approach to brain hemisphere functions in schizophrenia

The present paper proposes a new psychophysiological approach to the genesis of positive and negative schizophrenic symptoms. According to this approach, the initial factor in schizophrenic disorders is a functional insufficiency of the right hemisphere which can be determined by early emotional experience in combination with subtle brain damage. This functional insufficiency causes (a) the inability to grasp and select information before its realization; and (b) the inability to produce a polysemantic context which is crucial for creativity, psychological defense, and the restoration of search activity, all of which determine psychophysiological adaptation to the environment. Right hemisphere insufficiency causes left hemisphere hyperactivity as an ineffective attempt to compensate for this functional deficiency. As a result, normal search activity is replaced by artificial search activity which is represented by "positive" symptoms, and which uses the predisposition of the left hemisphere's catecholamine system for its increased activity. The suggestion is made that cognitive impairment in schizophrenia (the inability to use appropriate previous information in relation to current perceptual input) is related to the competition between information processing which requires left hemisphere activity, and the formation of positive symptoms, also based on left hemisphere activity.