Time series models of intraindividual varibility

Issued as final reportUnited States. Dept. of Health and Human Service

Validated Intraclass Correlation Statistics to Test Item Performance Models

A new method, with an application program in Matlab code, is proposed for testing item performance models on empirical databases. This method uses data intraclass correlation statistics as expected correlations to which one compares simple functions of correlations between model predictions and observed item performance. The method rests on a data population model whose validity for the considered data is suitably tested, and has been verified for three behavioural measure databases. Contrarily to usual model selection criteria, this method provides an effective way of testing under-fitting and over-fitting, answering the usually neglected question "does this model suitably account for these data?

DNA Methylation Signatures of Depressive Symptoms in Middle-aged and Elderly Persons:Meta-analysis of Multiethnic Epigenome-wide Studies

IMPORTANCE Depressive disorders arise from a combination of genetic and environmental risk factors. Epigenetic disruption provides a plausible mechanism through which gene-environment interactions lead to depression. Large-scale, epigenome-wide studies on depression are missing, hampering the identification of potentially modifiable biomarkers.OBJECTIVE To identify epigenetic mechanisms underlying depression in middle-aged and elderly persons, using DNA methylation in blood.DESIGN, SETTING, AND PARTICIPANTS To date, the first cross-ethnic meta-analysis of epigenome-wide association studies (EWAS) within the framework of the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium was conducted. The discovery EWAS included 7948 individuals of European origin from 9 population-based cohorts. Participants who were assessed for both depressive symptoms and whole-blood DNA methylation were included in the study. Results of EWAS were pooled using sample-size weighted meta-analysis. Replication of the top epigenetic sites was performed in 3308 individuals of African American and European origin from 2 population-based cohorts.MAIN OUTCOMES AND MEASURES Whole-blood DNA methylation levels were assayed with Illumina-Infinium Human Methylation 450K BeadChip and depressive symptoms were assessed by questionnaire.RESULTS The discovery cohorts consisted of 7948 individuals (4104 [51.6%] women) with a mean (SD) age of 65.4 (5.8) years. The replication cohort consisted of 3308 individuals (2456 [74.2%) women) with a mean (SD) age of 60.3 (6.4) years. The EWAS identified methylation of 3 CpG sites to be significantly associated with increased depressive symptoms: cg04987734 (P = 1.57 x 10(-)(08); n = 11 256; CDC42BPB gene), cg12325605 (P = 5.24 x 10(-09); n = 11256; ARHGEF3 gene), and an intergenic CpG site cg14023999 (P = 5.99 x 10(-)(08); n = 11256; chromosome = 15q261). The predicted expression of the CDC42BPB gene in the brain (basal ganglia) (effect, 0.14; P = 2.7 x 10(-03)) and of ARHGEF3 in fibroblasts (effect. -0.48; P = 9.8 x 10(-)(04) ) was associated with major depression.CONCLUSIONS AND RELEVANCE This study identifies 3 methylated sites associated with depressive symptoms. All 3 findings point toward axon guidance as the common disrupted pathway in depression. The findings provide new insights into the molecular mechanisms underlying the complex pathophysiology of depression. Further research is warranted to determine the utility of these findings as biomarkers of depression and evaluate any potential role in the pathophysiology of depression and their downstream clinical effects. (C) 2018 American Medical Association. All lights reserved

Factors influencing word naming in younger and older adults.

The present s udy examined age differences in the influence of3 factors that previous research has shown to influence word-naming performance. The influence of word frequency, orthographic length, and orthographic neighborhood measures was examined using large-scale r gression a alyses on the naming latencies for 2,820 words. Thirty-one younger adults and 29 older adults named all of these words, and age differences in the influence of these factors were examined. The results revealed that all 3 factors predicted reliable amounts ofvariance inword-naming latencies for both groups. However, older adults showed a larger influence of word frequency and reduced influences of orthographic length and orthographic neighborhood density compared with younger adults. Overall, these results uggest that lexical level factors increase ininfluence inolder adults whereas sublexical factors decrease in influence. Although the change of linguistic knowledge and skills early in the life span is well documented, the change in language processes later in life has not been a central focus in developmental psycho-linguistics. Of course, the change in language processing from middle to late adulthood occurs at a much slower ate and appears to be considerably ess profound than that found in children