The goal of this paper is to illustrate the application of the tools of genetic epidemiology, particularly the family study method, to inform the classification of psychiatric disorders in adults and children. The first section describes family studies of adults designed to investigate the causes of comorbidity of anxiety and depression. The analysis of familial traits provides stronger evidence for the validity of certain sub-types of anxiety and mood disorders that co-occur within the same individual and within families. The second section presents an example of the use of the family study method to examine the validity of the autism spectrum disorders (ASD). A review of these studies suggests that the most consistently familial traits in ASD are language and communication skills, insistence on sameness and non-verbal IQ. These are also the traits most commonly associated with the differentiation of autism from Asperger disorder and PDDNOS using both cross-sectional and longitudinal studies. From these data, a new classification system of the ASDs is proposed based on these familial traits.
"Here, we examined whether maternal hospitalization with infection during pregnancy, type of infection, and timing of infection influences risk of ASD in the largest study to-date. In a subsample of the Swedish population with information on ASD co-morbid with or without intellectual disability, we further examined the associations of prenatal infection with these different subtypes of ASD (Szatmari et al., 2007). "
[Show abstract][Hide abstract] ABSTRACT: Animal models indicate that maternal infection during pregnancy can result in behavioral abnormalities and neuropathologies in offspring. We examined the association between maternal inpatient diagnosis with infection during pregnancy and risk of ASD in a Swedish nationwide register-based birth cohort born 1984-2007 with follow-up through 2011. In total, the sample consisted of 2,371,403 persons with 24,414 ASD cases. Infection during pregnancy was defined from ICD codes. In the sample, 903 mothers of ASD cases (3.7%) had an inpatient diagnosis of infection during pregnancy. Logistic regression models adjusted for a number of covariates yielded odds ratios indicating approximately a 30% increase in ASD risk associated with any inpatient diagnosis of infection. Timing of infection did not appear to influence risk in the total Swedish population, since elevated risk of ASD was associated with infection in all trimesters. In a subsample analysis, infections were associated with greater risk of ASD with intellectual disability than for ASD without intellectual disability. The present study adds to the growing body of evidence, encompassing both animal and human studies, that supports possible immune-mediated mechanisms underlying the etiology of ASD.
"Since information on DSM or ICD subcategories was not readily available in all registers, we could not ASD according to these classifications. However, as boundaries between subcategories are not clearly supported in literature , we instead defined ASD according to DSM-V work group recommendations , and used an empirically supported division based on co-morbid intellectual disability . Another limitation is that our case validation was based on case-note review rather than direct clinical assessment. "
[Show abstract][Hide abstract] ABSTRACT: Reports of rising prevalence of autism spectrum disorders (ASD), along with their profound personal and societal burden, emphasize the need of methodologically sound studies to explore their causes and consequences. We here present the design of a large intergenerational resource for ASD research, along with population-based prevalence estimates of ASD and their diagnostic validity.
The Stockholm Youth Cohort is a record-linkage study comprising all individuals aged 0-17 years, ever resident in Stockholm County in 2001-2007 (N = 589,114). ASD cases (N = 5,100) were identified using a multisource approach, involving registers covering all pathways to ASD diagnosis and care, and categorized according to co-morbid intellectual disability. Prospectively recorded information on potential determinants and consequences of ASD were retrieved from national and regional health and administrative registers. Case ascertainment was validated through case-note review, and cross validation with co-existing cases in a national twin study.
The 2007 year prevalence of ASD in all children and young people was 11.5 per 1,000 (95% confidence interval 11.2-11.8), with a co-morbid intellectual disability recorded in 42.6% (41.0-44.2) of cases. We found 96.0% (92.0-98.4) of reviewed case-notes being consistent with a diagnosis of ASD, and confirmed ASD in 85.2% (66.2-95.8) of affected twins.
Findings from this contemporary study accords with recently reported prevalence estimates from Western countries at around 1%, based on valid case ascertainment. The Stockholm Youth Cohort, in light of the availability of extensive information from Sweden's registers, constitutes an important resource for ASD research. On-going work, including collection of biological samples, will enrich the study further.
PLoS ONE 07/2012; 7(7):e41280. DOI:10.1371/journal.pone.0041280 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Severe mental illnesses such as schizophrenia and mood disorders have a major impact on public health. Disease prevalence and phenotypic expression are the products of environment and gene interactions. However, our incomplete understanding of their aetiology and pathophysiology thwarts primary prevention and early diagnosis and limits the effective application of currently available treatments as well as the development of novel therapeutic approaches. Neuroimaging can provide detailed in vivo information about the biological mechanisms underpinning the relationship between genetic variation and clinical phenotypes or response to treatment. However, the biological complexity of severe mental illness results from unknown or unpredictable interactions between multiple genetic and environmental factors, many of which have only been partially identified. We propose that the use of epidemiological principles to neuroimaging research is a necessary next step in psychiatric research. Because of the complexity of mental disorders and the multiple risk factors involved only the use of large epidemiologically defined samples will allow us to study the broader spectrum of psychopathology, including sub-threshold presentation and explore pathophysiological processes and the functional impact of genetic and non-genetic factors on the onset and persistence of psychopathology.
European Psychiatry 07/2008; 23(4):315-9. DOI:10.1016/j.eurpsy.2007.09.014 · 3.44 Impact Factor
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