Evaluation of delay discounting as a transdiagnostic research domain criteria indicator in 1388 general community adults.

BACKGROUND: The Research Domain Criteria (RDoC) approach proposes a novel psychiatric nosology using transdiagnostic dimensional mechanistic constructs. One candidate RDoC indicator is delay discounting (DD), a behavioral economic measure of impulsivity, based predominantly on studies examining DD and individual conditions. The current study sought to evaluate the transdiagnostic significance of DD in relation to several psychiatric conditions concurrently. METHODS: Participants were 1388 community adults (18-65) who completed an in-person assessment, including measures of DD, substance use, depression, anxiety, posttraumatic stress disorder, and attention-deficit hyperactivity disorder (ADHD). Relations between DD and psychopathology were examined with three strategies: first, examining differences by individual condition using clinical cut-offs; second, examining DD in relation to latent psychopathology variables via principal components analysis (PCA); and third, examining DD and all psychopathology simultaneously via structural equation modeling (SEM). RESULTS: Individual analyses revealed elevations in DD were present in participants screening positive for multiple substance use disorders (tobacco, cannabis, and drug use disorder), ADHD, major depressive disorder (MDD), and an anxiety disorder (ps < 0.05-0.001). The PCA produced two latent components (substance involvement v. the other mental health indicators) and DD was significantly associated with both (ps < 0.001). In the SEM, unique significant positive associations were observed between the DD latent variable and tobacco, cannabis, and MDD (ps < 0.05-0.001). CONCLUSIONS: These results provide some support for DD as a transdiagnostic indicator, but also suggest that studies of individual syndromes may include confounding via comorbidities. Further systematic investigation of DD as an RDoC indicator is warranted.

Consistent evidence of indirect effects of impulsive delay discounting and negative urgency between childhood adversity and adult substance use in two samples.

RATIONALE: Exposure to adverse life experiences (ACEs) is robustly associated with problematic alcohol and other drug use. In addition, both ACEs and substance use have been independently associated with impulsivity. OBJECTIVE: To examine whether impulsivity is implicated in the link between ACE and adult substance use in two samples. METHODS: The primary sample was a cohort of community adults (N = 1431) who completed a one-time in-person assessment. A second sample was crowdsourced using Amazon Mechanical Turk (N = 3021). All participants were assessed for ACEs using the Adverse Childhood Experience Questionnaire and for current alcohol and other drug use. Given its multidimensional nature, impulsivity was assessed using the UPPS-P measure of impulsive personality traits, Go/NoGo (GNG) task (in-person community adult sample only), and delay discounting (Monetary Choice Questionnaire [MCQ] in the community adults and Effective Delay-50 [ED50] in the crowdsourced sample. Structural equation modeling was used to examine the hypothesized indirect effects for the measures of impulsivity between ACEs and substance use. RESULTS: In the community adults, significant indirect effects were observed from ACEs to substance use via UPPS-Negative Urgency (ß = 0.07, SE = 0.02, 95% CI [0.04, 0.10]), and the MCQ (ß = 0.02 SE = .01, 95% CI [0.01, 0.03]). In the crowdsourced sample, significant indirect effects were observed from ACEs to substance use via UPPS-Negative Urgency (ß = 0.05, SE = .01, 95% CI [0.04, 0.07]), UPPS-Premeditation (ß = 0.04, SE = .01, 95% CI [0.02, 0.05), and the ED50 (ß = 0.02, SE = .01; 95% CI [0.01, 0.03]). CONCLUSION: These findings provide consistent evidence that decrements in regulation of negative emotions and overvaluation of immediate rewards indirectly link ACE and substance use. These robust cross-sectional findings support the need for elucidating the underlying neural substrates implicated and for longitudinal evaluations.

Whole egg consumption and cortical bone in healthy children.

Eggs contain bioactive compounds thought to benefit pediatric bone. This cross-sectional study shows a positive link between childhood egg intake and radius cortical bone. If randomized trials confirm our findings, incorporating eggs into children's diets could have a significant impact in preventing childhood fractures and reducing the risk of osteoporosis. INTRODUCTION: This study examined the relationships between egg consumption and cortical bone in children. METHODS: The cross-sectional study design included 294 9-13-year-old black and white males and females. Three-day diet records determined daily egg consumption. Peripheral quantitative computed tomography measured radius and tibia cortical bone. Body composition and biomarkers of bone turnover were assessed using dual-energy X-ray absorptiometry and ELISA, respectively. RESULTS: Egg intake was positively correlated with radius and tibia cortical bone mineral content (Ct.BMC), total bone area, cortical area, cortical thickness, periosteal circumference, and polar strength strain index in unadjusted models (r = 0.144-0.224, all P < 0.050). After adjusting for differences in race, sex, maturation, fat-free soft tissue mass (FFST), and protein intakes, tibia relationships were nullified; however, egg intake remained positively correlated with radius Ct.BMC (r = 0.138, P = 0.031). Egg intake positively correlated with total body bone mineral density, BMC, and bone area in the unadjusted models only (r = 0.119-0.224; all P < 0.050). After adjusting for covariates, egg intake was a positive predictor of radius FFST (ß = 0.113, P < 0.050) and FFST was a positive predictor of Ct.BMC (ß = 0.556, P < 0.050) in path analyses. There was a direct influence of egg on radius Ct.BMC (ß = 0.099, P = 0.035), even after adjusting for the mediator, FFST (ß = 0.137, P = 0.020). Egg intake was positively correlated with osteocalcin in both the unadjusted (P = 0.005) and adjusted (P = 0.049) models. CONCLUSION: If the positive influence of eggs on Ct.BMC observed in this study is confirmed through future randomized controlled trials, whole eggs may represent a viable strategy to promote pediatric bone development and prevent fractures.

Insulin Resistance Negatively Influences the Muscle-Dependent IGF-1-Bone Mass Relationship in Premenarcheal Girls.

CONTEXT: IGF-1 promotes bone growth directly and indirectly through its effects on skeletal muscle. Insulin and IGF-1 share a common cellular signaling process; thus, insulin resistance may influence the IGF-1-muscle-bone relationship. OBJECTIVE: We sought to determine the effect of insulin resistance on the muscle-dependent relationship between IGF-1 and bone mass in premenarcheal girls. DESIGN, SETTING, AND PARTICIPANTS: This was a cross-sectional study conducted at a university research center involving 147 girls ages 9 to 11 years. MAIN OUTCOME MEASURES: Glucose, insulin, and IGF-1 were measured from fasting blood samples. Homeostasis model assessment of insulin resistance (HOMA-IR) was calculated from glucose and insulin. Fat-free soft tissue (FFST) mass and bone mineral content (BMC) were measured by dual-energy x-ray absorptiometry. Our primary outcome was BMC/height. RESULTS: In our path model, IGF-1 predicted FFST mass (b = 0.018; P = .001), which in turn predicted BMC/height (b = 0.960; P < .001). IGF-1 predicted BMC/height (b = 0.001; P = .002), but not after accounting for the mediator of this relationship, FFST mass. The HOMA-IR by IGF-1 interaction negatively predicted FFST mass (b = -0.044; P = .034). HOMA-IR had a significant and negative effect on the muscle-dependent relationship between IGF-1 and BMC/height (b = -0.151; P = .047). CONCLUSIONS: Lean body mass is an important intermediary factor in the IGF-1-bone relationship. For this reason, bone development may be compromised indirectly via suboptimal IGF-1-dependent muscle development in insulin-resistant children.