Epidemiology of trauma and posttraumatic stress disorder in Mexico

Prevalence rates of trauma and posttraumatic stress disorder (PTSD) were estimated from a probability sample of 2,509 adults from 4 cities in Mexico. PTSD was assessed according to Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 1994) criteria using the Composite International Diagnostic Interview (CIDI; WHO, 1997). Lifetime prevalence of exposure and PTSD were 76% and 11.2%, respectively. Risk for PTSD was highest in Oaxaca (the poorest city), persons of lower socioeconomic status, and women. Conditional risk for PTSD was highest following sexual violence, but nonsexual violence and traumatic bereavement had greater overall impact because of their frequency. Of lifetime cases, 62% became chronic; only 42% received medical or professional care. The research demonstrates the importance of expanding the epidemiologic research base on trauma to include developing countries around the world.     

Electrophysiological correlates of observational learning in children

Observational learning is an important mechanism for cognitive and social development. However, the neurophysiological mechanisms underlying observational learning in children are not well understood. In this study, we used a probabilistic reward‐based observational learning paradigm to compare behavioral and electrophysiological markers of individual and observational reinforcement learning in 8‐ to 10‐year‐old children. Specifically, we manipulated the amount of observable information as well as children's similarity in age to the observed person (same‐aged child vs. adult) to examine the effects of similarity in age on the integration of observed information in children. We show that the feedback‐related negativity (FRN) during individual reinforcement learning reflects the valence of outcomes of own actions. Furthermore, we found that the feedback‐related negativity during observational reinforcement learning (oFRN) showed a similar distinction between outcome valences of observed actions. This suggests that the oFRN can serve as a measure of observational learning in middle childhood. Moreover, during observational learning children profited from the additional social information and imitated the choices of their own peers more than those of adults, indicating that children have a tendency to conform more with similar others (e.g. their own peers) compared to dissimilar others (adults). Taken together, our results show that children can benefit from integrating observable information and that oFRN may serve as a measure of observational learning in children.     

Alternative Approaches to Addressing Non-Normal Distributions in the Application of IRT Models to Personality Measures

It is generally assumed that the latent trait is normally distributed in the population when estimating logistic item response theory (IRT) model parameters. This assumption requires that the latent trait be fully continuous and the population homogenous (i.e., not a mixture). When this normality assumption is violated, models are misspecified, and item and person parameter estimates are inaccurate. When normality cannot be assumed, it might be appropriate to consider alternative modeling approaches: (a) a zero-inflated mixture, (b) a log-logistic, (c) a Ramsay curve, or (d) a heteroskedastic-skew model. The first 2 models were developed to address modeling problems associated with so-called quasi-continuous or unipolar constructs, which apply only to a subset of the population, or are meaningful at one end of the continuum only. The second 2 models were developed to address non-normal latent trait distributions and violations of homogeneity of error variance, respectively. To introduce these alternative IRT models and illustrate their strengths and weaknesses, we performed real data application comparing results to those from a graded response model. We review both statistical and theoretical challenges in applying these models and choosing among them. Future applications of these and other alternative models (e.g., unfolding, diffusion) are needed to advance understanding about model choice in particular situations.     

Latino College Student Adjustment: Does an Increased Presence Offset Minority‐Status and Acculturative Stresses?1

This study examined whether minority‐status stresses and acculturative stresses increase the risk of psychological maladjustment of Latino students at a university where Latinos constitute the largest ethnic group. Participants were 338 Latino (228 Mexican American, 110 Central American) college students who responded to a mailed survey. The results of 2 separate hierarchical regression analyses of psychological distress and well‐being, controlling for demographic (gender, socioeconomic status, and ethnicity). sociocultural (level of acculturation), college role (generic college stresses), and personal (academic self‐confidence) influences provided partial support for our hypothesis and demonstrated the incremental predictive validity of acculturative stresses, but not of minority‐status stresses. Results are discussed in terms of the variety of stresses that Latino college students are likely to experience.     

Sudden Unexpected Versus Violent Death and PTSD Symptom Development

Changes to posttraumatic stress disorder (PTSD) trauma criterion in the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM–5) have been an area of much scrutiny and debate. One of the proposed changes included removing sudden unexpected death (SUD) from the list of potentially traumatic events. This study tested the extent to which unexpected death differed from violent death and other traumas as measured by PTSD symptoms. Our results indicated a significant difference in symptom development between those experiencing sudden violent death and sudden unexpected, but nonviolent, death. Additional analyses at the DSM–IV symptom cluster level, as well as with Simms, Watson, and Doebbeling’s (2002) factor structure of PTSD symptoms, suggested further distinctions between event types and symptom development. The extent to which SUD should be included in the trauma criterion is considered.