The increasing prevalence of reported diagnoses of childhood psychiatric disorders: a descriptive multinational comparison.

The objective of this study is to compare the time trend of reported diagnoses of autism spectrum disorder (ASD), hyperkinetic disorder, Tourette's syndrome, and obsessive-compulsive disorder across four countries after standardizing the study period, diagnostic codes used to define the conditions and statistical analyses across countries. We use a population-based cohort, including all live-born children in Denmark, Finland, Sweden and Western Australia, from January 1, 1990, through December 31, 2007 and followed through December 31, 2011. The main outcome measure is age-specific prevalence of diagnoses reported to population-based registry systems in each country. We observe an increase in age-specific prevalence for reported diagnoses of all four disorders across birth-year cohorts in Denmark, Finland, Sweden, and (for ASD) Western Australia. Our results highlight the increase in the last 20 years in the number of children and families in contact with health care systems for diagnosis and services for an array of childhood neuropsychiatric disorders, a phenomenon not limited to ASD. Also, the age of diagnosis of the studied disorders was often much higher than what is known of the typical age of onset of symptoms, and we observe limited leveling off in the incidence rate with increasing age.

Neonatal levels of cytokines and risk of autism spectrum disorders: an exploratory register-based historic birth cohort study utilizing the Danish Newborn Screening Biobank.

The aim of the study was to analyze cytokine profiles in neonatal dried blood samples (n-DBSS) retrieved from The Danish Newborn Screening Biobank of children developing Autism Spectrum Disorders (ASD) later in life and controls. Samples of 359 ASD cases and 741 controls were analyzed using Luminex xMAP technology and clinical data were retrieved from nationwide registers. Findings showed that children developing ASD were more likely to have decreased levels of both T helper-1(Th-1)-like cytokines (i.e. IFN-γ) and Th-2like cytokines (i.e. IL-4, IL-10) which may suggest a depressed or hypoactive immune cell activity during neonatal period in ASD.

Using maternally reported data to investigate the association between early childhood infection and autism spectrum disorder: the importance of data source.

BACKGROUND: Childhood infections have been found to be associated with autism spectrum disorder (ASD) in previous studies using hospital data or medical records to identify infections. We aimed to replicate these findings using maternal reports of childhood infection. METHODS: We used the Danish National Birth Cohort consisting of 92 583 live singletons born from 1997 to 2003 in Denmark. ASD diagnoses were retrieved from the Danish Psychiatric Central Register, and a total of 945 children from the cohort were diagnosed with ASD. Data were analysed using Cox proportional hazards regression. We studied the association between ASD and maternal reports of infectious disease in the child from birth to 19 months. Furthermore, we performed secondary analyses using hospital registers to investigate the association between ASD and hospital contact in general as well as hospital contact for various infections. RESULTS: We did not find a general association between maternal reports of infectious illness and ASD. However, hospital contact for all causes was associated with an increased risk for an ASD diagnosis. Danish children with ASD do not appear to have a general pattern of illness from infection in early life, but do have more contact with medical specialists for infections and other indications compared with the general population. CONCLUSION: [corrected] Hospital data should be used cautiously when studying the co-morbidity of ASD; if the increased rate of hospital contact overall for children with ASD is not considered, then misleading interpretations might be made of observed associations between specific diseases and ASD.

Maternal infection requiring hospitalization during pregnancy and autism spectrum disorders.

Exposure to prenatal infection has been suggested to cause deficiencies in fetal neurodevelopment. In this study we included all children born in Denmark from 1980, through 2005. Diagnoses of autism spectrum disorders (ASDs) and maternal infection were obtained through nationwide registers. Data was analyzed using Cox proportional hazards regression. No association was found between any maternal infection and diagnosis of ASDs in the child when looking at the total period of pregnancy: adjusted hazard ratio = 1.14 (CI: 0.96-1.34). However, admission to hospital due to maternal viral infection in the first trimester and maternal bacterial infection in the second trimester were found to be associated with diagnosis of ASDs in the offspring, adjusted hazard ratio = 2.98 (CI: 1.29-7.15) and adjusted hazard ratio = 1.42 (CI: 1.08-1.87), respectively. Our results support prior hypotheses concerning early prenatal viral infection increasing the risk of ASDs.

Association of family history of autoimmune diseases and autism spectrum disorders.

OBJECTIVES: Recent studies suggest that familial autoimmunity plays a part in the pathogenesis of ASDs. In this study we investigated the association between family history of autoimmune diseases (ADs) and ASDs/infantile autism. We perform confirmatory analyses based on results from previous studies, as well as various explorative analyses. METHODS: The study cohort consisted of all of the children born in Denmark from 1993 through 2004 (689 196 children). Outcome data consisted of both inpatient and outpatient diagnoses reported to the Danish National Psychiatric Registry. Information on ADs in parents and siblings of the cohort members was obtained from the Danish National Hospital Register. The incidence rate ratio of autism was estimated by using log-linear Poisson regression. RESULTS: A total of 3325 children were diagnosed with ASDs, of which 1089 had an infantile autism diagnosis. Increased risk of ASDs was observed for children with a maternal history of rheumatoid arthritis and celiac disease. Also, increased risk of infantile autism was observed for children with a family history of type 1 diabetes. CONCLUSIONS: Associations regarding family history of type 1 diabetes and infantile autism and maternal history of rheumatoid arthritis and ASDs were confirmed from previous studies. A significant association between maternal history of celiac disease and ASDs was observed for the first time. The observed associations between familial autoimmunity and ASDs/infantile autism are probably attributable to a combination of a common genetic background and a possible prenatal antibody exposure or alteration in fetal environment during pregnancy.