Clarifying the relationship between mental illness and recidivism using machine learning: A retrospective study.

OBJECTIVE: There is currently inconclusive evidence regarding the relationship between recidivism and mental illness. This retrospective study aimed to use rigorous machine learning methods to understand the unique predictive utility of mental illness for recidivism in a general population (i.e.; not only those with mental illness) prison sample in the United States. METHOD: Participants were adult men (n = 322) and women (n = 72) who were recruited from three prisons in the Midwest region of the United States. Three model comparisons using Bayesian correlated t-tests were conducted to understand the incremental predictive utility of mental illness, substance use, and crime and demographic variables for recidivism prediction. Three classification statistical algorithms were considered while evaluating model configurations for the t-tests: elastic net logistic regression (GLMnet), k-nearest neighbors (KNN), and random forests (RF). RESULTS: Rates of substance use disorders were particularly high in our sample (86.29%). Mental illness variables and substance use variables did not add predictive utility for recidivism prediction over and above crime and demographic variables. Exploratory analyses comparing the crime and demographic, substance use, and mental illness feature sets to null models found that only the crime and demographics model had an increased likelihood of improving recidivism prediction accuracy. CONCLUSIONS: Despite not finding a direct relationship between mental illness and recidivism, treatment of mental illness in incarcerated populations is still essential due to the high rates of mental illnesses, the legal imperative, the possibility of decreasing institutional disciplinary burden, the opportunity to increase the effectiveness of rehabilitation programs in prison, and the potential to improve meaningful outcomes beyond recidivism following release.

Effects of Bundling Medication for Opioid Use Disorder With an mHealth Intervention Targeting Addiction: A Randomized Clinical Trial.

OBJECTIVE: Medication for opioid use disorder (MOUD) improves treatment retention and reduces illicit opioid use. A-CHESS is an evidence-based smartphone intervention shown to improve addiction-related behaviors. The authors tested the efficacy of MOUD alone versus MOUD plus A-CHESS to determine whether the combination further improved outcomes. METHODS: In an unblinded parallel-group randomized controlled trial, 414 participants recruited from outpatient programs were assigned in a 1:1 ratio to receive either MOUD alone or MOUD+A-CHESS for 16 months and were followed for an additional 8 months. All participants were on methadone, buprenorphine, or injectable naltrexone. The primary outcome was abstinence from illicit opioid use; secondary outcomes were treatment retention, health services use, other substance use, and quality of life; moderators were MOUD type, gender, withdrawal symptom severity, pain severity, and loneliness. Data sources were surveys comprising multiple validated scales, as well as urine screens, every 4 months. RESULTS: There was no difference in abstinence between participants in the MOUD+A-CHESS and MOUD-alone arms across time (odds ratio=1.10, 95% CI=0.90-1.33). However, abstinence was moderated by withdrawal symptom severity (odds ratio=0.95, 95% CI=0.91-1.00) and MOUD type (odds ratio=0.57, 95% CI=0.34-0.97). Among participants without withdrawal symptoms, abstinence rates were higher over time for those in the MOUD+A-CHESS arm than for those in the MOUD-alone arm (odds ratio=1.30, 95% CI=1.01-1.67). Among participants taking methadone, those in the MOUD+A-CHESS arm were more likely to be abstinent over time (b=0.28, SE=0.09) than those in the MOUD-alone arm (b=0.06, SE=0.08), although the two groups did not differ significantly from each other (∆b=0.22, SE=0.11). MOUD+A-CHESS was also associated with greater meeting attendance (odds ratio=1.25, 95% CI=1.05-1.49) and decreased emergency department and urgent care use (odds ratio=0.88, 95% CI=0.78-0.99). CONCLUSIONS: Overall, MOUD+A-CHESS did not improve abstinence relative to MOUD alone. However, MOUD+A-CHESS may provide benefits for subsets of patients and may impact treatment utilization.

Acceptability of Personal Sensing Among People With Alcohol Use Disorder: Observational Study.

BACKGROUND: Personal sensing may improve digital therapeutics for mental health care by facilitating early screening, symptom monitoring, risk prediction, and personalized adaptive interventions. However, further development and the use of personal sensing requires a better understanding of its acceptability to people targeted for these applications. OBJECTIVE: We aimed to assess the acceptability of active and passive personal sensing methods in a sample of people with moderate to severe alcohol use disorder using both behavioral and self-report measures. This sample was recruited as part of a larger grant-funded project to develop a machine learning algorithm to predict lapses. METHODS: Participants (N=154; n=77, 50% female; mean age 41, SD 11.9 years; n=134, 87% White and n=150, 97% non-Hispanic) in early recovery (1-8 weeks of abstinence) were recruited to participate in a 3-month longitudinal study. Participants were modestly compensated for engaging with active (eg, ecological momentary assessment [EMA], audio check-in, and sleep quality) and passive (eg, geolocation, cellular communication logs, and SMS text message content) sensing methods that were selected to tap into constructs from the Relapse Prevention model by Marlatt. We assessed 3 behavioral indicators of acceptability: participants' choices about their participation in the study at various stages in the procedure, their choice to opt in to provide data for each sensing method, and their adherence to a subset of the active methods (EMA and audio check-in). We also assessed 3 self-report measures of acceptability (interference, dislike, and willingness to use for 1 year) for each method. RESULTS: Of the 192 eligible individuals screened, 191 consented to personal sensing. Most of these individuals (169/191, 88.5%) also returned 1 week later to formally enroll, and 154 participated through the first month follow-up visit. All participants in our analysis sample opted in to provide data for EMA, sleep quality, geolocation, and cellular communication logs. Out of 154 participants, 1 (0.6%) did not provide SMS text message content and 3 (1.9%) did not provide any audio check-ins. The average adherence rate for the 4 times daily EMA was .80. The adherence rate for the daily audio check-in was .54. Aggregate participant ratings indicated that all personal sensing methods were significantly more acceptable (all P<.001) compared with neutral across subjective measures of interference, dislike, and willingness to use for 1 year. Participants did not significantly differ in their dislike of active methods compared with passive methods (P=.23). However, participants reported a higher willingness to use passive (vs active) methods for 1 year (P=.04). CONCLUSIONS: These results suggest that active and passive sensing methods are acceptable for people with alcohol use disorder over a longer period than has previously been assessed. Important individual differences were observed across people and methods, indicating opportunities for future improvement.

Acute nicotine abstinence amplifies subjective withdrawal symptoms and threat-evoked fear and anxiety, but not extended amygdala reactivity.

Tobacco smoking imposes a staggering burden on public health, underscoring the urgency of developing a deeper understanding of the processes that maintain addiction. Clinical and experience-sampling data highlight the importance of anxious withdrawal symptoms, but the underlying neurobiology has remained elusive. Mechanistic work in animals implicates the central extended amygdala (EAc)-including the central nucleus of the amygdala and the neighboring bed nucleus of the stria terminalis-but the translational relevance of these discoveries remains unexplored. Here we leveraged a randomized trial design, well-established threat-anticipation paradigm, and multidimensional battery of assessments to understand the consequences of 24-hour nicotine abstinence. The threat-anticipation paradigm had the expected consequences, amplifying subjective distress and arousal, and recruiting the canonical threat-anticipation network. Abstinence increased smoking urges and withdrawal symptoms, and potentiated threat-evoked distress, but had negligible consequences for EAc threat reactivity, raising questions about the translational relevance of prominent animal and human models of addiction. These observations provide a framework for conceptualizing nicotine abstinence and withdrawal, with implications for basic, translational, and clinical science.

College students' momentary stress and prescription drug misuse in daily life: Testing direct links and the moderating roles of global stress and coping.

Prior survey-based research has documented associations between greater levels of stress and increased prescription drug misuse behaviour. These studies uniformly rely on assessments of both the stress experiences and the substance behaviour after they occurred (commonly spanning 6-12 month retrospective timeframes). Less is known about the extent to which variations in momentary stress predict the actual occurrence of prescription misuse in daily life among college students with elevated risk for engaging in the behaviour. In this study, 297 participants (69% females; Mage  = 19.5 years, SDage  = 0.71) completed a 28-day ecological momentary assessment procedure that collected self-reported stress and other contextual experiences in moments preceding prescription drug misuse. Analyses tested the within-person association between momentary stress and prescription drug misuse and examined the extent to which the relation between stress and misuse was moderated by participants' assigned sex or global stress and coping levels. Results from hierarchical generalised linear modelling indicated a significant within-person association between momentary stress (i.e., higher than usual relative to one's own mean) and greater likelihood of prescription misuse in daily life, accounting for the number of stressors and timing covariates. No significant moderation by participant sex was found, and moderation effects by global stress and coping levels were not in the expected directions. Direct results highlight the role of momentary stress experiences on health-relevant substance behaviours and provide future directions for research and applied efforts.

Alcohol's effects during uncertain and uncontrollable stressors in the laboratory.

Alcohol's effects on reactivity to stressors depends on the nature of the stressor and the reactivity being assessed. Research identifying characteristics of stressors that modulate reactivity and clarifies the neurobehavioral, cognitive, and affective components of this reactivity may help prevent, reduce or treat the negative impacts of acute and chronic alcohol use with implications for other psychopathology involving maladaptive reactivity to stressors. We used a novel, multi-measure, cued electric shock stressor paradigm in a greater university community sample of adult recreational drinkers to test how alcohol (N=64), compared to No-alcohol (N=64), effects reactivity to stressors that vary in both their perceived certainty and controllability. Preregistered analyses suggested alcohol significantly dampened subjective anxiety (self-report) and defensive reactivity (startle potentiation) more during uncertain than during certain stressors regardless of controllability, suggesting that stressor uncertainty -but not uncontrollability- may be sufficient to enhance alcohol's stress reactivity dampening and thus negative reinforcement potential.

Central stress response among deprived and continuing marijuana users and nonusers.

OBJECTIVE: We examined central nervous system [CNS] stress responses among deprived and continuing heavy marijuana users and nonusers. METHOD: Participants (N = 210; 46.7% female; Mage = 21.99; 91.4% White, 94.3% Non-Hispanic) were heavy marijuana users (N = 134) and nonusers (N = 76). Heavy users were randomly assigned to a 3-day marijuana deprivation condition (N = 68) or to continue using regularly (N = 66). Participants completed two threat-of-shock stressor tasks that manipulated stressor predictability by varying shock probability or timing. We measured central stress responses via startle potentiation (stressor conditions minus matched no-stressor condition). We examined two group contrasts (heavy use: all heavy users vs. nonusers; deprivation: deprived vs. continuing heavy users) on startle potentiation overall and moderated by stressor predictability (unpredictable vs. predictable). RESULTS: Deprivation did not affect startle potentiation overall (timing task: p = .184; probability task: p = .328) or differently by stressor predictability (timing task: p = .147; probability task: p = .678). Heavy use did not affect startle potentiation overall (timing task: p = .213; probability task: p = .843) or differently by stressor predictability (timing task: p = .655; probability task: p = .273). Posthoc analyses showed mixed evidence of general startle reactivity × deprivation interaction on startle potentiation overall (timing task: p = .019; probability task: p = .056) and differently by stressor predictability (probability task: p = .024; timing task: p = .364). CONCLUSIONS: A history of marijuana use or acute deprivation did not alter central stress responses despite prominent theoretical expectations. This study adds to growing research on central stress responses in individuals with a history of drug use and begins to parse moderating roles of individual differences and stressor characteristics. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Effect of an eHealth intervention on older adults' quality of life and health-related outcomes: a randomized clinical trial.

BACKGROUND: By 2030, the number of US adults age ≥65 will exceed 70 million. Their quality of life has been declared a national priority by the US government. OBJECTIVE: Assess effects of an eHealth intervention for older adults on quality of life, independence, and related outcomes. DESIGN: Multi-site, 2-arm (1:1), non-blinded randomized clinical trial. Recruitment November 2013 to May 2015; data collection through November 2016. SETTING: Three Wisconsin communities (urban, suburban, and rural). PARTICIPANTS: Purposive community-based sample, 390 adults age ≥65 with health challenges. EXCLUSIONS: long-term care, inability to get out of bed/chair unassisted. INTERVENTION: Access (vs. no access) to interactive website (ElderTree) designed to improve quality of life, social connection, and independence. MEASURES: Primary outcome: quality of life (PROMIS Global Health). Secondary: independence (Instrumental Activities of Daily Living); social support (MOS Social Support); depression (Patient Health Questionnaire-8); falls prevention (Falls Behavioral Scale). Moderation: healthcare use (Medical Services Utilization). Both groups completed all measures at baseline, 6, and 12 months. RESULTS: Three hundred ten participants (79%) completed the 12-month survey. There were no main effects of ElderTree over time. Moderation analyses indicated that among participants with high primary care use, ElderTree (vs. control) led to better trajectories for mental quality of life (OR=0.32, 95% CI 0.10-0.54, P=0.005), social support received (OR=0.17, 95% CI 0.05-0.29, P=0.007), social support provided (OR=0.29, 95% CI 0.13-0.45, P<0.001), and depression (OR= -0.20, 95% CI -0.39 to -0.01, P=0.034). Supplemental analyses suggested ElderTree may be more effective among people with multiple (vs. 0 or 1) chronic conditions. LIMITATIONS: Once randomized, participants were not blind to the condition; self-reports may be subject to memory bias. CONCLUSION: Interventions like ET may help improve quality of life and socio-emotional outcomes among older adults with more illness burden. Our next study focuses on this population. TRIAL REGISTRATION: ClinicalTrials.gov ; registration ID number: NCT02128789.

Real-time momentary mood as a predictor of college students' prescription drug misuse in daily life: Direct links and the moderating role of background mental health.

The present study addressed calls for research to identify real-time predictors of prescription drug misuse (Schepis et al., 2020) by testing young adults' momentary reports of their negative mood and positive mood as predictors of event-level misuse in daily life. We implemented a 28-day ecological momentary assessment (EMA) procedure that collected individuals' mood and other contextual experiences in moments preceding prescription drug misuse. Consistent with models of problematic substance use as a means to reduce negativity (Khantzian, 1997), results from hierarchical generalized linear modeling (HGLM) indicated within-person links between higher than usual negative mood and greater likelihood of prescription misuse in daily life. Contrary to the hypothesis, misuse was also more likely when preceded by elevated positive mood. We found consistent support for the hypothesized between-person effects, with prescription misuse in daily life associated with higher average levels of negative mood, and lower average levels of positive mood, across the reporting period. We further predicted that individuals reporting greater levels of social anxiety, depression, and externalizing symptoms would evidence stronger links between their momentary negative mood and prescription misuse. Partial support for this moderation hypothesis was found, with the positive within-person link between negative mood and prescription misuse significantly stronger among individuals higher (vs. lower) on social anxiety and depression. Results provide support for intricate connections between young adults' momentary mood, mental health symptoms, and prescription drug misuse. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Stressor-elicited smoking and craving during a smoking cessation attempt.

Stressors can undermine smokers' attempts to quit smoking. Although contemporary theories and animal models support this idea, human research has struggled to demonstrate definitively the relationship between stressors and smoking. Researchers have employed more ecologically valid methods like ecological momentary assessment to address this question, but studies focusing explicitly on stressors remain sparse and findings inconsistent. The purpose of this study was to examine the effect of stressful event intensity on smoking and craving among cigarette smokers during a quit attempt. We conducted preregistered, complementary concurrent and prospective (i.e., 8-hour lag window between stressful event and outcomes) analyses to maximize statistical power and provide temporal ordering, respectively. We also conducted follow-up moderation (Lag × Stressful Event Intensity) analyses. We hypothesized that smokers would be more likely to report both smoking and craving as the intensity of stressful events increased. Cigarette smokers (N = 125; 77 male) were randomly assigned to take nicotine replacement therapy (NRT) or placebo and provided 4x daily self-reports during the first 2 weeks of a quit attempt. Stressful events increased craving and the probability of smoking in concurrent analyses, and lag moderated the effect of stressful event intensity in follow-up prospective lagged analyses. NRT reduced the probability of smoking but not craving and did not moderate the effect of stressful events on smoking or craving. This study supports a prospective relationship between stressful events and smoking/craving in situ and demonstrates that NRT does not reduce the impact of stressors on smoking or craving. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Prospective Prediction of Lapses in Opioid Use Disorder: Protocol for a Personal Sensing Study.

BACKGROUND: Successful long-term recovery from opioid use disorder (OUD) requires continuous lapse risk monitoring and appropriate use and adaptation of recovery-supportive behaviors as lapse risk changes. Available treatments often fail to support long-term recovery by failing to account for the dynamic nature of long-term recovery. OBJECTIVE: The aim of this protocol paper is to describe research that aims to develop a highly contextualized lapse risk prediction model that forecasts the ongoing probability of lapse. METHODS: The participants will include 480 US adults in their first year of recovery from OUD. Participants will report lapses and provide data relevant to lapse risk for a year with a digital therapeutic smartphone app through both self-report and passive personal sensing methods (eg, cellular communications and geolocation). The lapse risk prediction model will be developed using contemporary rigorous machine learning methods that optimize prediction in new data. RESULTS: The National Institute of Drug Abuse funded this project (R01DA047315) on July 18, 2019 with a funding period from August 1, 2019 to June 30, 2024. The University of Wisconsin-Madison Health Sciences Institutional Review Board approved this project on July 9, 2019. Pilot enrollment began on April 16, 2021. Full enrollment began in September 2021. CONCLUSIONS: The model that will be developed in this project could support long-term recovery from OUD-for example, by enabling just-in-time interventions within digital therapeutics. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/29563.

Real-time associations between young adults' momentary pain and prescription opioid misuse intentions in daily life.

Managing pain has been identified (mainly through retrospective reports) as a robust motivator for individuals engaging in prescription opioid misuse. However, surprisingly little work has directly examined whether momentary pain experiences are associated with prescription opioid misuse in daily life. Participants included 297 young-adult college students recruited on the basis of recent prescription drug misuse. Ecological momentary assessment over a 28-day period was utilized to collect participants' pain experiences and prescription opioid misuse intention and behavior. Hierarchical generalized linear modeling and binary logistic regression tested hypotheses. Findings revealed that higher in-the-moment pain was positively associated with intentions to engage in prescription opioid misuse, accounting for report timing and participant sex and background substance use. Also, the between-person result indicated that participants who reported higher levels of pain across the reporting period were more likely to intend to misuse prescription opioids in daily life. There was a similar reliable association between higher pain ratings across the reporting period and greater likelihood of engaging in misuse behavior, although actual misuse frequency was low. Reliable moderation was observed: As hypothesized, the within-person association between momentary pain and misuse intentions was stronger for females compared with males. Also, the within-person link between pain and misuse intentions was stronger for those who reported lower (vs. higher) levels of problematic alcohol use; this was not consistent with the hypothesized direction. Understanding the role of college students' pain in their intentions to engage in prescription opioid misuse is important for informing future research and prevention efforts. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Stress Allostasis in Substance Use Disorders: Promise, Progress, and Emerging Priorities in Clinical Research.

Clinicians and researchers alike have long believed that stressors play a pivotal etiologic role in risk, maintenance, and/or relapse of alcohol and other substance use disorders (SUDs). Numerous seminal and contemporary theories on SUD etiology posit that stressors may motivate drug use and that individuals who use drugs chronically may display altered responses to stressors. We use foundational basic stress biology research as a lens through which to evaluate critically the available evidence to support these key stress-SUD theses in humans. Additionally, we examine the field's success to date in targeting stressors and stress allostasis in treatments for SUDs. We conclude with our recommendations for how best to advance our understanding of the relationship between stressors and drug use, and we discuss clinical implications for treatment development.

Acute prazosin administration does not reduce stressor reactivity in healthy adults.

RATIONALE: Norepinephrine plays a critical role in the stress response. Clarifying the psychopharmacological effects of norepinephrine manipulation on stress reactivity in humans has important implications for basic neuroscience and treatment of stress-related psychiatric disorders, such as posttraumatic stress disorder and alcohol use disorders. Preclinical research implicates the norepinephrine alpha-1 receptor in responses to stressors. The No Shock, Predictable Shock, Unpredictable Shock (NPU) task is a human laboratory paradigm that is well positioned to test cross-species neurobiological stress mechanisms and advance experimental therapeutic approaches to clinical trials testing novel treatments for psychiatric disorders. OBJECTIVES: We hypothesized that acute administration of prazosin, a noradrenergic alpha-1 antagonist, would have a larger effect on reducing stress reactivity during unpredictable, compared to predictable, stressors in the NPU task. METHODS: We conducted a double-blind, placebo-controlled, crossover randomized controlled trial in which 64 healthy adults (32 female) completed the NPU task at two visits (2 mg prazosin vs. placebo). RESULTS: A single acute dose of 2 mg prazosin did not reduce stress reactivity in a healthy adult sample. Neither NPU startle potentiation nor self-reported anxiety was reduced by prazosin (vs. placebo) during unpredictable (vs. predictable) stressors. CONCLUSIONS: Further research is needed to determine whether this failure to translate preclinical neuroscience to human laboratory models is due to methodological factors (e.g., acute vs. chronic drug administration, brain penetration, study population) and/or suggests limited clinical utility of noradrenergic alpha-1 antagonists for treating stress-related psychiatric disorders.

Acute alcohol administration dampens central extended amygdala reactivity.

Alcohol use is common, imposes a staggering burden on public health, and often resists treatment. The central extended amygdala (EAc)-including the bed nucleus of the stria terminalis (BST) and the central nucleus of the amygdala (Ce)-plays a key role in prominent neuroscientific models of alcohol drinking, but the relevance of these regions to acute alcohol consumption in humans remains poorly understood. Using a single-blind, randomized-groups design, multiband fMRI data were acquired from 49 social drinkers while they performed a well-established emotional faces paradigm after consuming either alcohol or placebo. Relative to placebo, alcohol significantly dampened reactivity to emotional faces in the BST. To rigorously assess potential regional differences in activation, data were extracted from unbiased, anatomically predefined regions of interest. Analyses revealed similar levels of dampening in the BST and Ce. In short, alcohol transiently reduces reactivity to emotional faces and it does so similarly across the two major divisions of the human EAc. These observations reinforce the translational relevance of addiction models derived from preclinical work in rodents and provide new insights into the neural systems most relevant to the consumption of alcohol and to the initial development of alcohol abuse in humans.

Heavy marijuana use but not deprivation is associated with increased stressor reactivity.

Although stressors appear to motivate marijuana use, and marijuana use, in turn, is believed to induce stress system neuroadaptations, relatively little empirical work has explicitly tested for stress neuroadaptations associated with heavy marijuana use. We examined stressor reactivity to threat of unpredictable electric shock via startle potentiation among heavy marijuana users and a control group that reported minimal history of marijuana use. Heavy marijuana users were randomly assigned to 3 days of marijuana deprivation or no deprivation. This design allowed us to test contrasts for heavy (vs. minimal) use and deprivation (vs. no deprivation) on stressor reactivity. Heavy marijuana users (both deprived and nondeprived) displayed increased startle potentiation during threat of unpredictable electric shock relative to minimal use controls. In contrast, marijuana deprivation had no effect on startle potentiation. Startle potentiation was also increased among users who reported greater stress-coping motives for their marijuana use and users with cannabis use disorder diagnoses. To our knowledge, this is the 1st study to demonstrate increased reactivity to unpredictable stressors among heavy marijuana users. However, comparable increased unpredictable stressor reactivity among patients with alcohol and other substance use disorders has been previously documented. This relationship to heavy marijuana use is consistent with predictions from rodent addiction models regarding stress neuroadaptations following heavy, chronic drug use but could also represent an etiologically relevant premorbid risk characteristic. Finally, the clinical import of unpredictable stressor reactivity is reinforced by its relationships with stress-coping motives and cannabis use disorder status. (PsycINFO Database Record

Robust is not necessarily reliable: From within-subjects fMRI contrasts to between-subjects comparisons.

Advances in cognitive and affective neuroscience come largely from within-subjects comparisons, in which the functional significance of neural activity is determined by contrasting two or more experimental conditions. Clinical and social neuroscience studies have attempted to leverage between-subject variability in such condition differences to better understand psychopathology and other individual differences. Shifting from within-to between-subjects comparisons requires that measures have adequate internal consistency to function as individual difference variables. This is particularly relevant for difference scores-which have lower reliability. The field has assumed reasonable internal consistency of neural measures based on consistent findings across studies (i.e., if a within-subject difference in neural activity is robust, then it must be reliable). Using one of the most common fMRI paradigms in the clinical neuroscience literature (i.e., a face- and shape-matching task), in a large sample of adolescents (N = 139) we replicate a robust finding: amygdala activation is greater for faces than shapes. Moreover, we demonstrate that the internal consistency of the amygdala in face and shape blocks was excellent (Spearman-Brown corrected reliability [SB] > .94). However, the internal consistency of the activation difference between faces and shapes was nearly zero (SB = -.06). This reflected the fact that the amygdala response to faces and shapes was highly correlated (r = .97) across individuals. Increased neural activation to faces versus shapes could not possibly function as an individual difference measure in these data-illustrating how neural activation can be robust within subjects, but unreliable as an individual difference measure. Strong and reproducible condition differences in neural activity are not necessarily well-suited for individual differences research-and neuroimaging studies should always report the internal consistency of, and correlations between, activations used in individual differences research.

Linear mixed-effects models and the analysis of nonindependent data: A unified framework to analyze categorical and continuous independent variables that vary within-subjects and/or within-items.

In this article we address a number of important issues that arise in the analysis of nonindependent data. Such data are common in studies in which predictors vary within "units" (e.g., within-subjects, within-classrooms). Most researchers analyze categorical within-unit predictors with repeated-measures ANOVAs, but continuous within-unit predictors with linear mixed-effects models (LMEMs). We show that both types of predictor variables can be analyzed within the LMEM framework. We discuss designs with multiple sources of nonindependence, for example, studies in which the same subjects rate the same set of items or in which students nested in classrooms provide multiple answers. We provide clear guidelines about the types of random effects that should be included in the analysis of such designs. We also present a number of corrective steps that researchers can take when convergence fails in LMEM models with too many parameters. We end with a brief discussion on the trade-off between power and generalizability in designs with "within-unit" predictors. (PsycINFO Database Record