Maternal age and infantile autism

A High Prevalence of Autism Spectrum Disorder in Preschool Children in an Immigrant, Multiethnic Population in Sweden: Challenges for Health Care

This study examines the prevalence of autism spectrum disorder (ASD) in preschool children in an immigrant population. Possible risk factors for ASD and individual needs for the children and their families are described, as well as implications for health care. The estimated minimum prevalence for ASD in the area was 3.66% for children aged 2–5 years. Multiple risk factors and extensive individual needs for the children and their families were observed. The high prevalence of ASD and the plethora of needs in immigrant communities pose challenges for health care. A coordinated health care system is necessary to meet the many and individual needs.

Genetic and Epigenetic Etiology Underlying Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a pervasive neurodevelopmental disorder characterized by difficulties in social interaction, language development delays, repeated body movements, and markedly deteriorated activities and interests. Environmental factors, such as viral infection, parental age, and zinc deficiency, can be plausible contributors to ASD susceptibility. As ASD is highly heritable, genetic risk factors involved in neurodevelopment, neural communication, and social interaction provide important clues in explaining the etiology of ASD. Accumulated evidence also shows an important role of epigenetic factors, such as DNA methylation, histone modification, and noncoding RNA, in ASD etiology. In this review, we compiled the research published to date and described the genetic and epigenetic epidemiology together with environmental risk factors underlying the etiology of the different phenotypes of ASD.

Clinical Pattern of Autism in Nigeria

Autism, a global disorder has been widely studied in the Western world. However, there are limited studies on its occurrence, risk factors, and presentation in developing countries such as Nigeria. This retrospective study highlights the pattern of presentation of autism and presence of some risk factors in 75 Nigerian cases referred to a private autism center. The diagnosis of autism was made using Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM IV), International Classification of Diseases Fourth edition, the Modified Checklist for Autism in Toddlers, Autism Treatment Evaluation Checklist, and Childhood Autism Rating Scale. There were 60 males and 15 females with a male to female ratio of 4:1. The mean age at presentation to the center was 6.87 ± 4.20 years and majority (91.9%) belonged to a high socioeconomic class. Already established risk factors, clinical features, and comorbidities of autism present among the study group were similar to findings in individuals with autism in other parts of the world.

Minor physical anomalies in adults with autism spectrum disorder and healthy controls

Minor Physical Anomalies (MPAs) are subtle abnormalities of the head, face, and limbs, without significant cosmetic or functional impact to the individual. They are assumed to represent external markers of developmental deviations during foetal life. MPAs have been suggested to indicate severity in mental illness and constitute external markers for atypical brain development. Higher frequencies of MPAs can be found in children with autism. The aims of the present study were to examine the prevalence and patterns of MPAs in adults with autism spectrum disorder (ASD) and to investigate whether MPAs are associated with symptom severity and overall functioning. Fifty adults with ASD and intelligence within the normal range and 53 healthy controls were examined with the Waldrop scale, an instrument for assessing MPAs. Face and feet were photographed enabling blinded assessment. Significant differences between the ASD and the control group were found on the MPA total scores, and also in the craniofacial region scores. Moreover, the shape of the ears was associated with autistic traits, in the ASD group. High MPA total scores were associated with poorer functioning. The findings suggest a link between MPAs, autistic traits, and level of functioning. Assessment of MPAs may assist in the diagnostic procedure of psychiatric disorders.

Maternal and paternal age are jointly associated with childhood autism in Jamaica

Several studies have reported maternal and paternal age as risk factors for having a child with Autism Spectrum Disorder (ASD), yet the results remain inconsistent. We used data for 68 age- and sex-matched case-control pairs collected from Jamaica. Using Multivariate General Linear Models (MGLM) and controlling for parity, gestational age, and parental education, we found a significant (p < 0.0001) joint effect of parental ages on having children with ASD indicating an adjusted mean paternal age difference between cases and controls of [5.9 years; 95% CI (2.6, 9.1)] and a difference for maternal age of [6.5 years; 95% CI (4.0, 8.9)]. To avoid multicollinearity in logistic regression, we recommend joint modeling of parental ages as a vector of outcome variables using MGLM.

Pre-, peri- and neonatal risk factors for autism

OBJECTIVE

To identify pre-, peri- and neonatal risk factors for pervasive developmental disorders (PDD).

METHODS

We searched the Medline database through March 2011 for relevant case-control and population-based studies on pre-, peri- and neonatal hazards related to PDD, including autism. We identified 85 studies for this review. Data were extracted systematically and organized according to risk factors related to family history, pregnancy, gestational age, delivery, birth milestones and the neonate's condition at birth.

RESULTS

During the prenatal period, risk factors for PDD were advanced maternal or paternal ages, being firstborn vs. third or later, maternal prenatal medication use and mother's status as foreign born. During the perinatal and neonatal periods, the risk factors for PDD were preterm birth, breech presentation, planned cesarean section, low Apgar scores, hyperbilirubinemia, birth defect and a birthweight small for gestational age. The influence of maternal pre-eclampsia, diabetes, vomiting, infections and stress during pregnancy requires further study in order to determine risk for PDD.

DISCUSSION

Despite evidence for the association of some pre-, peri- and neonatal risk factors associated with PDD, it remains unclear whether these risks are causal or play a secondary role in shaping clinical expression in individuals with genetic vulnerability. A plausible hypothsesis is that improvements in obstetric and neonatal management have led to an increased rate of survivors with pre-existing brain damage. Given the variety of risk factors, we propose that future studies should investigate combinations of multiple factors, rather than focusing on a single factor.

Perinatal and neonatal risk factors for autism: a comprehensive meta-analysis

BACKGROUND

The etiology of autism is unknown, although perinatal and neonatal exposures have been the focus of epidemiologic research for over 40 years.

OBJECTIVE

To provide the first review and meta-analysis of the association between perinatal and neonatal factors and autism risk.

METHODS

PubMed, Embase, and PsycInfo databases were searched for studies that examined the association between perinatal and neonatal factors and autism through March 2007. Forty studies were eligible for the meta-analysis. For each exposure, a summary effect estimate was calculated using a random-effects model. Heterogeneity in effect estimates across studies was examined, and, if found, a meta-regression was conducted to identify measured methodological factors that could explain between-study variability.

RESULTS

Over 60 perinatal and neonatal factors were examined. Factors associated with autism risk in the meta-analysis were abnormal presentation, umbilical-cord complications, fetal distress, birth injury or trauma, multiple birth, maternal hemorrhage, summer birth, low birth weight, small for gestational age, congenital malformation, low 5-minute Apgar score, feeding difficulties, meconium aspiration, neonatal anemia, ABO or Rh incompatibility, and hyperbilirubinemia. Factors not associated with autism risk included anesthesia, assisted vaginal delivery, postterm birth, high birth weight, and head circumference.

CONCLUSIONS

There is insufficient evidence to implicate any 1 perinatal or neonatal factor in autism etiology, although there is some evidence to suggest that exposure to a broad class of conditions reflecting general compromises to perinatal and neonatal health may increase the risk. Methodological variations were likely sources of heterogeneity of risk factor effects across studies.

Prenatal and perinatal risk factors for autism in China

We conducted a case–control study using 190 Han children with and without autism to investigate prenatal and perinatal risk factors for autism in China. Cases were recruited through public special education schools and controls from regular public schools in the same region (Tianjin), with frequency matching on sex and birth year. Unadjusted analyses identified seven prenatal and seven perinatal risk factors significantly associated with autism. In the adjusted analysis, nine risk factors showed significant association with autism: maternal second-hand smoke exposure, maternal chronic or acute medical conditions unrelated to pregnancy, maternal unhappy emotional state, gestational complications, edema, abnormal gestational age (<35 or >42 weeks), nuchal cord, gravidity >1, and advanced paternal age at delivery (>30 year-old).

Paternal age increases the risk for autism in an Iranian population sample

Background

Autism is a neurodevelopmental disorder which is known to have a strong genetic component and is most likely oligogenic. However, the necessary role of environmental factors has been well documented. Prior research suggests that parental characteristics, such as age and level of education, may be associated with a risk of autism. Parental age has been shown to be associated with many disorders, such as schizophrenia, childhood cancer and fetal death. However, results from studies of parental age and autism are inconsistent.

Methods

In the present study, we investigated the association of autism with parental age in 179 autism cases and 1611 matched cohort children from Iran. Each case was matched with nine cohort controls on parental education, sex, order of birth, consanguineous marriage, urbanism and province of residence. The Cox regression model was used to carry out conditional logistic regression on the matched data.

Results

There was a significant association between higher paternal age, but not maternal age, and an increasing risk of autism. An analysis of the combined effect of parental age and education also revealed that parents with higher education had an increased risk of having autistic children, with a dose-response effect of parental age.

Conclusions

This study, which is the first epidemiological study of autism in Iran, provides evidence of the association of paternal age and risk of autism.

An immunoreactive theory of selective male affliction

Males are selectively afflicted with the neurodevelopmental and psychiatric disorders of childhood, a broad and virtually ubiquitous phenomenon that has not received proper attention in the biological study of sex differences. The previous literature has alluded to psychosocial differences, genetic factors and elements pertaining to male “complexity” and relative immaturity, but these are not deemed an adequate explanation for selective male affliction. The structure of sex differences in neurodevelopmental disorders is hypothesized to contain these elements: (1) Males are more frequently afflicted, females more severely; (2) disorders arising in females are largely mediated by the genotype; in males, by a genotype by environment interaction; (3) complications of pregnancy and delivery occur more frequently with male births; such complications are decisive and influence subsequent development. We hypothesize that there is something about the male fetus that evokes an inhospitable uterine environment. This “evocative principle” is hypothesized to relate to the relative antigenicity of the male fetus, which may induce a state of maternal immunoreactivity, leading either directly or indirectly to fetal damage. The immunoreactive theory (IMRT) thus constructed is borrowed from studies of sex ratios and is the only explanation consistent with negative parity effects in the occurrence of pregnancy complications and certain neurodevelopmental disorders. Although the theory is necessarily speculative, it is heuristic and hypotheses derived from it are proposed; some are confirmed in the existing literature and by the authors' research.

Risk of autism and increasing maternal and paternal age in a large north American population

Previous studies are inconsistent regarding whether there are independent effects of maternal and paternal age on the risk of autism. Different biologic mechanisms are suggested by maternal and paternal age effects. The study population included all California singletons born in 1989-2002 (n = 7,550,026). Children with autism (n = 23,311) were identified through the California Department of Developmental Services and compared with the remainder of the study population, with parental ages and covariates obtained from birth certificates. Adjusted odds ratios and 95% confidence intervals were used to evaluate the risk of autism associated with increasing maternal and paternal age. In adjusted models that included age of the other parent and demographic covariates, a 10-year increase in maternal age was associated with a 38% increase in the odds ratio for autism (odds ratio = 1.38, 95% confidence interval: 1.32, 1.44), and a 10-year increase in paternal age was associated with a 22% increase (odds ratio = 1.22, 95% confidence interval: 1.18, 1.26). Maternal and paternal age effects were seen in subgroups defined by race/ethnicity and other covariates and were of greater magnitude among first-born compared with later-born children. Further studies are needed to help clarify the biologic mechanisms involved in the independent association of autism risk with increasing maternal and paternal age.

Prenatal risk factors for autism: comprehensive meta-analysis

BACKGROUND

The aetiology of autism is unknown, although prenatal exposures have been the focus of epidemiological research for over 40 years.

AIMS

To provide the first quantitative review and meta-analysis of the association between maternal pregnancy complications and pregnancy-related factors and risk of autism.

METHOD

PubMed, Embase and PsycINFO databases were searched for epidemiological studies that examined the association between pregnancy-related factors and autism. Forty studies were eligible for inclusion in the meta-analysis. Summary effect estimates were calculated for factors examined in multiple studies.

RESULTS

Over 50 prenatal factors have been examined. The factors associated with autism risk in the meta-analysis were advanced parental age at birth, maternal prenatal medication use, bleeding, gestational diabetes, being first born v. third or later, and having a mother born abroad. The factors with the strongest evidence against a role in autism risk included previous fetal loss and maternal hypertension, proteinuria, pre-eclampsia and swelling.

CONCLUSIONS

There is insufficient evidence to implicate any one prenatal factor in autism aetiology, although there is some evidence to suggest that exposure to pregnancy complications may increase the risk.

The role of rare structural variants in the genetics of autism spectrum disorders

Autism is a neurodevelopmental disorder characterized by impaired social interaction and communication and restricted interests and behaviors. Despite high estimates of heritability, genetic causes of ASD have long been elusive, due in part to a high degree of genetic and phenotypic heterogeneity (Bailey et al., 1995). Recently, important advances have been made in the genetics of ASD with the use of new technologies for the direct detection of copy number variation (CNV) in the human genome. CNV studies have revealed that de novo deletions and duplications, typically less than 1 Mb in size, are strongly associated with ASD, suggesting that spontaneous structural mutations play a more important role in the etiology of disease than was previously recognized. Rare mutations have been identified at many different locations in the genome, and multiple 'hot spots' have been identified where identical rearrangements recur with high frequency. These findings are consistent with the hypothesis that autism, like mental retardation, is caused by a large number of individually rare mutations. These studies serve as a model for how other emerging technologies for mutation detection (e.g. next generation sequencing platforms) could be used to further elucidate the role of rare sequence changes in ASD.

Advanced paternal age is associated with impaired neurocognitive outcomes during infancy and childhood

BACKGROUND

Advanced paternal age (APA) is associated with an increased risk of neurodevelopmental disorders such as autism and schizophrenia, as well as with dyslexia and reduced intelligence. The aim of this study was to examine the relationship between paternal age and performance on neurocognitive measures during infancy and childhood.

METHODS AND FINDINGS

A sample of singleton children (n = 33,437) was drawn from the US Collaborative Perinatal Project. The outcome measures were assessed at 8 mo, 4 y, and 7 y (Bayley scales, Stanford Binet Intelligence Scale, Graham-Ernhart Block Sort Test, Wechsler Intelligence Scale for Children, Wide Range Achievement Test). The main analyses examined the relationship between neurocognitive measures and paternal or maternal age when adjusted for potential confounding factors. Advanced paternal age showed significant associations with poorer scores on all of the neurocognitive measures apart from the Bayley Motor score. The findings were broadly consistent in direction and effect size at all three ages. In contrast, advanced maternal age was generally associated with better scores on these same measures.

CONCLUSIONS

The offspring of older fathers show subtle impairments on tests of neurocognitive ability during infancy and childhood. In light of secular trends related to delayed fatherhood, the clinical implications and the mechanisms underlying these findings warrant closer scrutiny.

Parental ages at birth of children with pervasive developmental disorders are higher than those of children in the general population

To examine whether parental ages at birth of children with pervasive developmental disorders (PDD) are elevated, maternal/paternal ages at birth of 309 PDD children born in 1993-2003 (mean age, 8.4 years) were compared with those of children in the Japanese national statistics (general population). The mean maternal/paternal ages (years) at birth of PDD children of 31.7/34.6 were significantly higher even than the highest mean maternal/paternal ages at birth of children of 31.2/33.6 in the national statistics in 2003. This first Japanese study to report elevated parental ages at birth of PDD children underscores the need of further extensive studies.

Brief Report: Effect of Maternal Age on Severity of Autism

The etiology of autism is complex, consisting of unknown genetic and environmental factors. Previous studies have revealed that maternal age is increased in autism compared to controls, making it a possible risk factor. This study examined the effects of maternal age on autism severity using IQ as a measure of cognitive severity and selected subtests of the Child Behavior Checklist (CBCL) as measures of social severity. A sample of 154 subjects with autism spectrum disorders was obtained from the Stanford Neuropsychiatry/Pervasive Developmental Disorder (PDD) clinic. Results indicate that there is no relationship between IQ or selected CBCL subtests and maternal age, suggesting that maternal age does not influence the severity of autism as measured by these indicators.

Sociodemographic Risk Factors for Autism in a US Metropolitan Area

The present study examined the association between autism and sociodemographic factors, overall and in subgroups of children with autism with and without mental retardation (Autism/MR and Autism/No MR, respectively); the association was further examined in subanalyses by child's source of ascertainment to assess the presence of ascertainment bias. In the main analyses, one marker of higher social class (higher median family income) was significantly associated with autism overall. Both markers of higher social class (higher maternal education and higher median family income) were significantly associated with autism/no MR, but not associated with autism/MR. In the subanalyses, associations with social class varied by ascertainment source. Future studies should consider phenotypic subgroups of children with autism and must consider potential ascertainment bias.

Imbalanced genomic imprinting in brain development: an evolutionary basis for the aetiology of autism

We describe a new hypothesis for the development of autism, that it is driven by imbalances in brain development involving enhanced effects of paternally expressed imprinted genes, deficits of effects from maternally expressed genes, or both. This hypothesis is supported by: (1) the strong genomic-imprinting component to the genetic and developmental mechanisms of autism, Angelman syndrome, Rett syndrome and Turner syndrome; (2) the core behavioural features of autism, such as self-focused behaviour, altered social interactions and language, and enhanced spatial and mechanistic cognition and abilities, and (3) the degree to which relevant brain functions and structures are altered in autism and related disorders. The imprinted brain theory of autism has important implications for understanding the genetic, epigenetic, neurological and cognitive bases of autism, as ultimately due to imbalances in the outcomes of intragenomic conflict between effects of maternally vs. paternally expressed genes.

Neurodevelopmental Disabilities

The topic of this chapter is neurodevelopmental disabilities, with discussion focused on three prototypic neurodevelopmental disorders: mental retardation, autism, and cerebral palsy. These disorders are highlighted because the epidemiologic knowledge is more advanced; however, many of the important methodologic issues apply to other neurodevelopmental disorders. The chapter discusses the particular research challenges in achieving complete case ascertainment due to the problems of case finding and case confirmation. It presents information about the prevalence of each of these disorders and temporal changes in frequency over time, as well as the possible factors contributing to increased recognition of these disorders. The chapter summarizes investigations of risk factors for each disorder, including genetic factors and possible environmental etiologies.

Descriptive epidemiology of autism in a California population: who is at risk?

We investigated the association between selected infant and maternal characteristics and autism risk. Children with autism born in California in 1989-1994 were identified through service agency records and compared with the total population of California live births for selected characteristics recorded on the birth certificate. Multivariate models were used to generate adjusted risk estimates. From a live birth population of more than 3.5 million, 4381 children with autism were identified. Increased risks were observed for males, multiple births, and children born to black mothers. Risk increased as maternal age and maternal education increased. Children born to immigrant mothers had similar or decreased risk compared with California-born mothers. Environmental factors associated with these demographic characteristics may interact with genetic vulnerability to increase the risk of autism.

Descriptive epidemiology of autism in a California population: who is at risk?

We investigated the association between selected infant and maternal characteristics and autism risk. Children with autism born in California in 1989-1994 were identified through service agency records and compared with the total population of California live births for selected characteristics recorded on the birth certificate. Multivariate models were used to generate adjusted risk estimates. From a live birth population of more than 3.5 million, 4381 children with autism were identified. Increased risks were observed for males, multiple births, and children born to black mothers. Risk increased as maternal age and maternal education increased. Children born to immigrant mothers had similar or decreased risk compared with California-born mothers. Environmental factors associated with these demographic characteristics may interact with genetic vulnerability to increase the risk of autism.

Brief report: incidence of and risk factors for autistic disorder in neonatal intensive care unit survivors

We investigated prospectively the incidence of autistic disorder (AD) in the neonatal intensive care unit and the risk factors associated with autistic development. The study population included the 5,271 children at St. Mary's Hospital and the diagnosis of AD was performed using DSM-III-R criteria. A total of 36 prenatal, perinatal, and postnatal factors were evaluated in the patients with AD, 57 cerebral palsy (CP), and 214 controls. AD was identified in 18 of the 5,271 children and the incidence was 34 per 10,000 (0.34%). This value was more than twice the highest prevalence value previously reported in Japan. Children with AD had a significantly higher history of the meconium aspiration syndrome (p = .0010) than the controls. Autistic patients had different risk factors than CP.

Psychophysiological aspects of autistic disorders: overview

The neurological, neurochemical, and neurotransmitter level differences as well as genetic influences associated with autism have been studied extensively in the last two decades. The varied findings from research offer hope for better understanding, effective treatment, and, perhaps, cure of this pervasive developmental disorder.

Autism as a strongly genetic disorder: evidence from a British twin study

Two previous epidemiological studies of autistic twins suggested that autism was predominantly genetically determined, although the findings with regard to a broader phenotype of cognitive, and possibly social, abnormalities were contradictory. Obstetric and perinatal hazards were also invoked as environmentally determined aetiological factors. The first British twin sample has been re-examined and a second total population sample of autistic twins recruited. In the combined sample 60% of monozygotic (MZ) pairs were concordant for autism versus no dizygotic (DZ) pairs; 92% of MZ pairs were concordant for a broader spectrum of related cognitive or social abnormalities versus 10% of DZ pairs. The findings indicate that autism is under a high degree of genetic control and suggest the involvement of multiple genetic loci. Obstetric hazards usually appear to be consequences of genetically influenced abnormal development, rather than independent aetiological factors. Few new cases had possible medical aetiologies, refuting claims that recognized disorders are common aetiological influences.

A comparative study of development and symptoms among disintegrative psychosis and infantile autism with and without speech loss

To investigate clinical pictures and the validity of disintegrative psychosis (DP) as defined in ICD-9, 18 cases of DP were compared with 51 and 145 cases of infantile autism (IA) with and without speech loss, respectively, on clinical variables. The DP cases showed clearer regression after more satisfactory development than the IA cases with speech loss. Around age 7, about 4 years after regression, those with DP were significantly more severely retarded than those with IA, yet both were similar in autistic symptomatology. EEG abnormalities and mothers 30 or older at delivery were significantly more common in the histories of those with DP than of those with IA. DP may be linked with IA having speech loss with regression in mental development as a common denominator.

Maternal age and birth defects: a population study

Since more and more women in developed countries are delaying childbearing to an older age, it is important to find out whether birth defects, other than those resulting from chromosomal anomalies, are related to maternal age. We have studied all 26,859 children with birth defects of unknown aetiology identified among 576,815 consecutive livebirths in British Columbia. All these cases' records were linked with provincial birth records to allow determination of maternal age at birth. We excluded children with chromosomal anomalies and those with other birth defects of known aetiology. Only 3 of the 43 birth defect categories studied showed significant maternal-age-specific trends: there were decreasing linear trends with maternal age for patent ductus arteriosus (chi 2 = 36.65, 1 df, p less than 0.01) and hypertrophic pyloric stenosis (chi 2 = 4.90, 1 df, p less than 0.05) and a bell-shaped curve (risk increasing to maternal age 30 then falling) for congenital dislocatable hip/hip click. The findings from this population-based analysis of no association between the incidence of birth defects of unknown aetiology and advancing maternal age should be reassuring to healthy women who opt to delay childbearing.

Is autism more common now than ten years ago?

A total population study of children, aged 13 years and under, suggested that there has been an apparent rise in the frequency of autistic disorder and autistic-like conditions (excluding Asperger's syndrome) in one area of western Sweden over the last ten years. The frequency was 4.0/100,000 in 1980, 7.5/10,000 in 1984 and 11.6/10,000 in 1988 in the city of Göteborg. Even though the prevalence rates refer to slightly different age cohorts, it was concluded that the apparent increase is in part due to better detection, but also to new cases born to immigrant parents. Typical cases of autistic disorder accounted for 75% of cases, and 20% had normal or near-normal IQs.

Mental retardation in urban children: a population study of reduced optimality in the pre-, peri- and neonatal periods

One hundred and thirty representative cases of mentally retarded children in Sweden were surveyed in order to detect reductions in optimality in the prenatal, perinatal and postnatal periods. There was a small but statistically significant reduction in optimality, particularly pertaining to the prenatal and neonatal periods. It is of interest, however, that these mentally retarded children had smaller reductions of optimality than did children with cerebral palsy or infantile autism.

New perspectives in autism, Part II: The differential diagnosis and neurobiology of autism

The clinical spectrum of autism spans a broad range of functions, but the core symptoms remain the same regardless of the intelligence of the child: the autistic type of social deficit that ranges from a lack of inclination to relate to extreme difficulty with the mechanics of social interactions, a global communication deficit that involves both verbal and nonverbal modes, and a severe cognitive deficit involving concept formation (abstraction) that is combined with an exceptional memory for factual information. These symptoms may vary dramatically in severity, but the basic deficits are identifiable regardless of IQ. Under-recognition of autism is a major problem at all IQs, but especially in patients with IQs above 50. No drugs have been found to significantly improve the core deficits in autism. Antipsychotics should be avoided except for short-term use. Antidepressants, anxiolytics, and anticonvulsants are important in the treatment of depression, affective modulation, situation-related stress, and seizures. Intensive social skills training is assuming a prominent role in behavior modification programs, and success with higher-functioning autistic children suggests that outcome can be improved by intensive training. The neurobiology of autism has also undergone dramatic changes. The psychogenic theories of etiology have been completely invalidated. Autism is now considered to be a neurological disorder resulting from an error in brain development. The precise location and nature of this deficit are still being actively debated and investigated. One theory emphasizes a dysfunction of the limbic system that results in an impairment in the acquisition of information. A second theory proposes a primary role for dysfunction of the cortical association network responsible for the processing of information.

Outcome and prognostic factors in infantile autism and similar conditions: a population-based study of 46 cases followed through puberty

This follow-up study reports data from a population-based series of children in the Göteborg region of Sweden diagnosed in childhood as suffering from infantile autism and other childhood psychoses and followed through to the ages of 16-23 years. The results of the study are in good accord with the only previous population-based study of the same kind. IQ at diagnosis and communicative speech development before 6 years were the most important prognostic factors, but other trends were seen that also compare favorably with previous studies. Some previously unreported trends also emerged.

The organic etiology of infantile autism: a critical review of the literature

Various theories have been provided in the literature regarding the etiology of infantile autism. It seems that the biological causation dominates the thinking of mental health practitioners and researchers irrespective of discipline. Areas of research include the following: neuropathological studies of the brain, autopsies, electroencephalograms, epileptic seizures, brain lateralization, studies in asymmetry; neurochemistry; genetics; and pre-, peri- and postnatal factors. A critical analysis of these studies has indicated that the evidence of organic factors tends to be rather weak and furthermore has been found to be contradictory. It is felt that the major problem lies in the fact that a large number of investigators include in their sampling children with various mental and physical disabilities and label them autistic. In general, there seems to be little information regarding the selection and little background information is offered on these children. It is suggested that a standardized and world wide diagnostic system be constructed which will provide objective etiological results.