Assessing the dimensionality of the CES-D using multi-dimensional multi-level Rasch models

<div><p>Objectives</p><p>The CES-D is a widely used depression screening instrument. While numerous studies have analysed its psychometric properties using exploratory and various kinds of confirmatory factor analyses, only few studies used Rasch models and none a multidimensional one.</p><p>Methods</p><p>The present study applies a multidimensional Rasch model using a sample of 518 respondents representative for the Austrian general population aged 18 to 65. A one-dimensional model, a four-dimensional model reflecting the subscale structure suggested by [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0197908#pone.0197908.ref001" target="_blank">1</a>], and a four-dimensional model with the background variables gender and age were applied.</p><p>Results</p><p>While the one-dimensional model showed relatively good fit, the four-dimensional model fitted much better. EAP reliability indices were generally satisfying and the latent correlations varied between 0.31 and 0.88. In the analysis involving background variables, we found a limited effect of the participants’ gender. DIF effects were found unveiling some peculiarities. The two-items subscale Interpersonal Difficulties showed severe weaknesses and the Positive Affect subscale with the reversed item wordings also showed unexpected results.</p><p>Conclusions</p><p>While a one-dimensional over-all score might still contain helpful information, the differentiation according to the latent dimension is strongly preferable. Altogether, the CES-D can be recommended as a screening instrument, however, some modifications seem indicated.</p></div

Infit measures of the one-dimensional model.

<p>Notes: The bold line shows the item infit with bullets indicating significant values. The dotted lines indicate the infit values of the three thresholds (labelled with 1, 2, and 3; slightly horizontally displaced for better readability).The bold horizontal line indicates the ideal value of 1 and the two dashed horizontal lines the limits of acceptability (0.7 to 1.3). Numbers in circles indicate significant thresholds (note that the significance also depends on the standard error of the respective estimate, hence, significant values need not be located outside the acceptability limits and similar values need not be significant at the same time). The (r) indicates that the item codings had to be reversed prior to evaluation, because these items were positively worded. The items along the horizontal axis are sorted according to the four subscales with dotted vertical lines showing the subscale blocks with their original number in brackets.</p

Information based fit indices for the one- and the four-dimenensional model.

<p>Information based fit indices for the one- and the four-dimenensional model.</p

Regression coefficients of the latent background model.

<p>Regression coefficients of the latent background model.</p

Items considered problematic in studies applying an IRT model to the CES-D.

<p>Bullets indicate items with a significant infit index, bullets and counts in brackets indicate partially problematic items with suspicious thresholds (i.e., significant or outside the critical limits) only.</p

Person-item map of the one-dimensional model.

<p>The upper part shows the histogram of the person parameter distribution and the lower plot the location of the Thurstonian thresholds, both sharing the same metric. The red lines in the lower diagram indicate the average threshold of each item, constituting a measure of the “difficulty”of this item. Items are sorted according to subscales as indicated by Radloff (1977).</p

Differential item functioning due to gender and depression.

<p>Notes: The dots represent the DIF-Effect, i.e., the item parameter difference between the two groups; error bars indicate the 95% confidence interval; Bullets indicate a significant DIF-Effect for the respective item. Values below 0 means that the item is rather preferred by men, items with DIF-values above 0 are rather preferred by women. The solid line indicates DIF according to sex and the dashed line indicates DIF according to depression. In the latter case, item 2 had to be omitted due to technical reasons (see text). For better readability, the two curves were horizontally displaced.</p

Infit measures of the four-dimensional model.

<p>For notes see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0197908#pone.0197908.g002" target="_blank">Fig 2</a>.</p

Correlations of the latent subscales.

<p>Note: The entries in the main diagonal (italicized) are the variance of each subscale.</p

Comparing forensic and non-forensic women with schizophrenia spectrum disorders: a European study

Studies about violence by women with severe mental disorders are rare. The aim of this paper is to analyse the sample of women diagnosed with Schizophrenia Spectrum Disorders (SSD) from the EU-VIORMED study who had offended violently and were admitted to forensic facilities (cases), and compare them to women with SSD who never exhibited violent behaviour (controls). Cases and controls matched for age and diagnosis were compared for sociodemographic, clinical, neuropsychological, and treatment-related characteristics using a standardised assessment. When compared to 36 controls, the 26 cases were significantly older, with longer duration of illness, had fewer years of education, were less likely to have children, and were more likely to have a comorbid personality disorder. Cases were less functionally impaired and scored lower on cognitive domains. There were no differences between the groups in exposure to childhood or adult violence, but a greater proportion of cases reported more frequently being witness to and victims of violence and more frequently reported being beaten, kicked, or punched. Results suggest that the emergence of violent behaviour in women with SSD might be shaped by various factors including violent victimisation, personality factors, soft cognitive impairment and perhaps as a result a more extended duration of illness.</p