Arv og miljø ved oligofreni

Third World adversity: African infant precocity and the role of environment

The war against illiteracy has not been won. The number of illiterates approaches a billion. Most reside in Third World countries--former colonies--where they are caught in a poverty trap of disease, low agricultural production and environmental adversity requiring technology beyond their means. I argue against the commonly held view that this is mainly attributable to the four hundred years of traffic in men. According to the late K.O. Dike, middle men along the African coast barred foreign merchants from the hinterland, and because of this the social, political structure and sovereignty of the African states remained fundamentally unchanged during the period 1400-1807, whereas a few decades after colonisation the socio-political system collapsed and was replaced by a small rich elite and many poor, while resources were taken out of Africa. Present poverty and underdevelopment represent as great a challenge as the trade in slaves. As did the African Middle-Men of that time, African leaders now must unite in an ambitious and confident Pan-African Union demonstrating strength. Western countries should focus on reducing poverty and improving nutrition. This also makes terrorism and legal and illegal migration less likely. Education is important, but the West should not limit its effort to fighting illiteracy but should also support the establishment of institutions for higher education. Africa possessed optimal conditions and an enriched environment for human evolution. African Infant Precocity is a persistent example. The human brain, like other brains, consists 60% of poly-unsaturated fatty acids (Marine-Fat), the rest being water. A sufficient amount is required to secure optimal brain growth. It normalizes brain function, and prevents sudden cardiac and infant death, which have been increasing in Western societies. Humans are unique in having a mismatch between the need for brain food--marine fat--and our common high protein diet. Nowhere is the neglect of the brain greater than in pregnancy when protein is the only major nutrient considered. Declining levels of polyunsaturated fatty acids have been observed in human milk. Deficient intake could, if not corrected, gradually impair brain function as has been seen in animal experiments.

Optimality of the birth population reduces learning and behaviour disorders and sudden infant death after the first month

The weight distribution pattern of all births can be divided into a "skewing to the left" to lower weights and high neonatal mortality, a "skewing to the right" to higher weights (>3500g) and minimum neonatal and postneonatal mortality, and a "symmetrical distribution" with mortality in between. This study was initiated with the hypothesis that a deficit in newborns of more than 3500 g would adversely affect postneonatal death. Higher and rising postneonatal mortality solely attributable to sudden infant death of unknown cause (sudden infant death syndrome; SIDS) was observed in the Nordic countries with a lower proportion of heavy newborns. Minor environmental intervention almost eliminated excess mortality from this cause, supporting raised susceptibility with a depressed birthweight in postneonatal SIDS. This contrasts with classical neonatal low birthweight SIDS, which is stable despite numerous attempts at reduction, supporting a multi-factorial aetiology: low maternal age, low education, low socioeconomic status, maternal smoking, infection, etc. The postneonatal SIDS epidemic associated with a deficit in heavy newborns is thought to be a result of changing behaviour in pregnancy: moderate iatrogenic dietary restriction and young women favouring a low-calorie, low-fat diet, especially in the third trimester when the foetus is most vulnerable, which delays myelination and somatic growth and renders the infant susceptible to minor morbidity and irregularity. The timing of death and neuropathological findings suggestive of repeated hypoxic episodes in more than 80% of cases of SIDS prior to death support this theory. The similar weight distribution patterns in SIDS and all births in Denmark, the UK and the USA suggest a substantial proportion of the neonates in these countries could be growth-retarded and at risk of hypoxic episodes in infancy. A few cases, particularly males (sex-ratio = 1.7), suffer SIDS, the majority survive. Many, mostly males, present minor CNS signs and learning and behaviour problems. The male predominance accords with males more than 500 g higher optimal birthweight than females and susceptibility to a depressed weight at birth. In order to prevent postneonatal dying, SIDS and reduce learning/behaviour disorders it is necessary to raise the proportion of heavy newborns by promoting foetal growth rate equal to the maternal intrinsic rate by eating to one's appetite a balanced diet, favouring a diet high in marine fat, especially in third trimester, in order to ensure maturation of the CNS and prolong gestation, thereby increasing birthweight. Although the increased survival of some very low birthweight neonates confounds the issue, a division between SIDS in neonatal and postneonatal death is recommended in order to assess the proportion of "avoidable infant death" as opposed to persistent classical neonatal SIDS.

Cerebral lateralisation and rate of maturation

Multifactorial inheritance applied to brain development implies a large continuum of normal variation with deviation from the norm at the extremes of maturational rate. The greater population of neurons, greater arborization of neural networks and excessive synaptic density in early maturation imply that adaptability (plasticity) is a main advantage, as opposed to a deficit in adaptability associated with the reduced number of neurons, reduced connectivity and reduced synaptic density in late slow maturation. It is hypothesised that Planum Temporale (PT) asymmetry and hand-preference predict the rate of CNS maturation as does the cognitive profile on the Wechsler Adult Intelligence Scale (WAIS): PT leftward asymmetry, right-handedness and a left-hemisphere cognitive advantage signifies early fast maturation: PT rightward asymmetry, left-handedness and a right-hemisphere cognitive advantage signify late maturation, while PT symmetry and ambilaterality represent rates of maturation in between. The slower development of males implies a male predominance in disorders affecting late maturers: Developmental Dyslexia (DD) with a predominance of rightward PT asymmetry/symmetry, left-handedness and multiple functional deficits, as well as excessive regressive events confirmed on PT/MRI. Schizophrenia, hypothesised to be a disorder in late maturers, is distinguished by rightward asymmetry/symmetry. Left-handedness and DD are common as is prior delayed development supporting excessive regressive events as do the findings on PT/MRI. To reduce the risk of DD and schizophrenia requires a reduction in late maturation through the enhancement of maturational rate by optimal nutrition before and during pregnancy and later.

Optimal foetal growth in the reduction of learning and behaviour disorder and prevention of sudden infant death (SIDS) after the first month

A theory is presented that a diet low in polyunsaturated fatty acids (PUFA) in the third trimester of pregnancy may delay myelination and brain maturation. This may underpin learning and behaviour disorders and sudden infant death (SIDS) after the first month, conditions that are associated with lower than average birthweight. Epidemiological evidence is reviewed showing an inverse relation between the proportion of heavy newborns (> 3500 g) and infant mortality rate. Some countries with a lower proportion of heavy newborns despite equally high standards of living and medical care have higher post-neonatal death rates. The higher rates are solely due to SIDS which has a peak mortality within 80-100 days. It is hypothesised that as this is a time when myelination peaks, SIDS may be due to maturational delay. Evidence of subtle CNS changes in brainstem structures and in the neuromuscular system supports an instability in brainstem control systems. Moderate iatrogenic dietary restriction predominates today, but a rising number of women favour a low-caloric low-fat diet especially in the third trimester when the foetus is most susceptible. This may lead to a depressed birthweight, delayed somatic growth and neuronal maturation, such as is observed in SIDS victims. The majority exposed to suboptimal conditions survive, but a few suffer SIDS; confirming post-neonatal susceptibility. Many, especially males, present minor CNS signs and learning/behaviour disorders that could be the sequelae of repeated hypoxic episodes, such as recorded in more than 80% of SIDS victims. To reduce learning/behaviour disorders and prevent death from SIDS after the first month, it is necessary to ensure optimal development by promoting foetal growth. It is advised to avoid unnecessary dieting and to favour a diet high in PUFAs, thus prolonging pregnancy and so increasing birthweight.

Age at puberty and mental illness. Towards a neurodevelopmental aetiology of Kraepelin's endogenous psychoses

The hypothesis of a neurodevelopmental aetiology of manic-depressive psychosis and schizophrenia is based on the relation between onset of puberty and the final regressive events in the central nervous system (elimination of 40% of neuronal synapses), and the discrepancy in body build in the two disorders which is similar to that between early- and late-maturing individuals. The marked rise in manic-depressive psychoses and decline in schizophrenia, particularly the non-paranoid categories, accompanying the decline in mean pubertal age by some four years during the past hundred years are taken as evidence that manic-depressive psychosis affects early maturers and schizophrenia particularly affects late maturers. Gender differences and social differentials accord with this theory. Redundancy of neuronal synapses characterises manic-depressive psychosis, and reduced density of synapses is a characteristic of schizophrenia, whereas 'normality', with optimal synaptic density, is in between.

Inbreeding and schizophrenia

The unique situation that the Norwegian 1891 census included information on consanguineous relation between spouses and that first admissions to psychiatric hospitals by diagnosis were available for the years 1921-40, formed the basis for the present study. There are similarities between the pattern of inbreeding and admission rates in our rural communities, but we were unable to demonstrate any significant correlation. This is interpreted as due to selective avoidance in the choice of a marriage partner, particularly between near relatives. Good neighbourhood knowledge was an important factor in our sparsely populated communities with a marriage pattern distinguished by extreme geographical proximity of residence of spouses. The considerably lower proportion of first cousin matings than expected among parents of psychiatric in-patients 1926-55, illustrates the lower psychiatric morbidity in offspring of consanguineous parentage. Admissions 1921-40 comprised only functional psychoses with a predominance of schizophrenia (greater than 80%), which today is diagnosed in less than 10%. A decline in incidence rate is not likely, whereas changing diagnostic practice is probably a main factor. The near disappearance of catatonia and hebephrenia could be related to the introduction of psychotropic drugs and the accompanying improvement in hospital treatment. The epidemiology of schizophrenia is unchanged with a significant excess in lower social classes. This could in part be due to schizophrenic phenocopies related to the unchanged social differential in infant mortality and morbidity (including a particular season of birth effect), in part to the prevalence of adverse environment postnatally. The considerably greater male marital differential has probably a social cause, whereas male earlier onset of disease and more severe course of the disease are discussed in relation to the new concept of progressive sexual brain differentiation.