Modeling Risk Factors for Intraindividual Variability: A Mixed-Effects Beta-Binomial Model Applied to Cognitive Function in Older People in the English Longitudinal Study of Ageing.

Cognitive functioning in older age profoundly impacts quality of life and health. While most research on cognition in older age has focused on mean levels, intraindividual variability (IIV) around this may have risk factors and outcomes independent of the mean value. Investigating risk factors associated with IIV has typically involved deriving a summary statistic for each person from residual error around a fitted mean. However, this ignores uncertainty in the estimates, prohibits exploring associations with time-varying factors, and is biased by floor/ceiling effects. To address this, we propose a mixed-effects location scale beta-binomial model for estimating average probability and IIV in a word recall test in the English Longitudinal Study of Ageing. After adjusting for mean performance, an analysis of 9,873 individuals across 7 (mean = 3.4) waves (2002-2015) found IIV to be greater at older ages, with lower education, in females, with more difficulties in activities of daily living, in later birth cohorts, and when interviewers recorded issues potentially affecting test performance. Our study introduces a novel method for identifying groups with greater IIV in bounded discrete outcomes. Our findings have implications for daily functioning and care, and further work is needed to identify the impact for future health outcomes.

A registered report of a two-site study of variations of the flanker task: ERN experimental effects and data quality.

Error-related negativity is a widely used measure of error monitoring, and many projects are independently moving ERN recorded during a flanker task toward standardization, optimization, and eventual clinical application. However, each project uses a different version of the flanker task and tacitly assumes ERN is functionally equivalent across each version. The routine neglect of a rigorous test of this assumption undermines efforts to integrate ERN findings across tasks, optimize and standardize ERN assessment, and widely apply ERN in clinical trials. The purpose of this registered report was to determine whether ERN shows similar experimental effects (correct vs. error trials) and data quality (intraindividual variability) during three commonly used versions of a flanker task. ERN was recorded from 172 participants during three versions of a flanker task across two study sites. ERN scores showed numerical differences between tasks, raising questions about the comparability of ERN findings across studies and tasks. Although ERN scores from all three versions of the flanker task yielded high data quality and internal consistency, one version did outperform the other two in terms of the size of experimental effects and the data quality. Exploratory analyses of the error positivity (Pe) provided tentative support for the other two versions of the task over the paradigm that appeared optimal for ERN. The present study provides a roadmap for how to statistically compare psychometric characteristics of ERP scores across paradigms and gives preliminary recommendations for flanker tasks to use for ERN- and Pe-focused studies.

'With or without you': associations between noteworthy events and cognitive complaints across 100 days.

OBJECTIVES: Daily noteworthy events have implications for physical and mental health, but less is known about the role daily events have for self-reported cognition and whether the involvement of close social partners differentiates these associations. The current study examined how daily positive and negative noteworthy events relate to subjective memory and attentional difficulties and whether close social partners moderated associations. METHOD: We used data from a 100-day microlongitudinal web-based study of 104 older adults (Nobservations=7,051; Mage=63.13 years, SDage=7.81, 88.46% Female). Participants reported on exposure to and valence of noteworthy events, involvement of close social partners, and subjective cognitive complaints at the end of each day. RESULTS: Logistic multilevel models revealed that days with a negative event were associated with increased odds of forgetting something and trouble concentrating whereas days with positive events were associated with decreased odds of trouble concentrating. Close social partner involvement did not moderate within-person associations. CONCLUSION: Our results suggest that day-to-day events are correlates of cognitive complaints regardless of close social partner involvement in the events. Research should clarify the role of daily positive and negative events in personalized interventions and determine whether this person-centered approach to self-reported cognitive health helps inform diagnostic practices.

Intraindividual Variability in Attention-Deficit/Hyperactivity Disorder: An Ex-Gaussian Approach.

Higher intraindividual variability (IIV) of response times is consistently noted in children with attention-deficit/hyperactivity disorder (ADHD). The current study investigated whether an ex-Gaussian estimate of IIV in children ages 6-13 years-old could differentiate between children with and without ADHD. Children completed a computerized go/no-go task to estimate trial-by-trial IIV and a continuous performance test (CPT) to estimate inattention and hyperactivity/impulsivity. Parents completed questionnaires assessing inattention and hyperactive/impulsive behaviors. IIV, commission errors, and attention problems as rated by parents were significantly greater in the ADHD group. Groups did not differ on errors of omission, but IIV was predictive of omission errors and parent ratings of inattention and hyperactivity/impulsivity. IIV predicted group membership (ADHD vs Control) whereas errors of omission did not. However, IIV did not improve diagnostic accuracy when parent ratings were used, such that parent ratings were superior at determining diagnosis. Current results support the use of IIV, based on the ex-Gaussian approach, as an objective measure of attention problems over omission errors on sustained attention CPT-type tasks. Additionally, while parent ratings of attention impairment remain the best predictor of ADHD diagnostic status, IIV may be helpful in determining when further assessment is required in the absence of those ratings.

Sleep regularity in healthy adolescents: Associations with sleep duration, sleep quality, and mental health.

Current evidence points to the importance of sleep for adolescent physical and mental health. To date, most studies have examined the association between sleep duration/quality and health in adolescence. An emerging line of research suggests that regularity in the timing of sleep may also play an important role in well-being. To address this aspect of sleep, the present study investigated daily variability of sleep, quantified using the sleep regularity index (SRI), in 46 adolescents (M = 12.78 ± 1.07 years) and its association with depressive symptoms/mental health. Sleep was measured during a 6 month period (M = 133.11 ± 36.42 nights) using actigraphs to quantify SRI values calculated for school days, weekends and holidays. Depressive symptoms and general psychopathology were assessed at the beginning (baseline) and end (follow-up) of the actigraphy measurements. Sleep was most regular during school days and associated with a longer total sleep time, shorter sleep onset latency, and higher sleep efficiency. Moreover, a higher SRI on school days was associated with fewer depressive symptoms at follow-up, whereas higher SRI on weekends was associated with less overall psychopathology at follow-up. Furthermore, the change in overall psychopathology, but not depressive symptoms across the two assessments was correlated with sleep regularity index. Our results suggest that regular timing of sleep is associated with sleep that is of longer duration and higher quality and may be protective of adolescent mental health. Therefore, adolescents should be encouraged not only to get enough sleep, but also to retain regular sleeping patterns to promote well-being and mental health.

Examining reaction time variability on the stop-signal task in the ABCD study.

OBJECTIVE: Reaction time variability (RTV) has been estimated using Gaussian, ex-Gaussian, and diffusion model (DM) indices. Rarely have studies examined interrelationships among these performance indices in childhood, and the use of reaction time (RT) computational models has been slow to take hold in the developmental psychopathology literature. Here, we extend prior work in adults by examining the interrelationships among different model parameters in the ABCD sample and demonstrate how computational models of RT can clarify mechanisms of time-on-task effects and sex differences in RTs. METHOD: This study utilized trial-level data from the stop signal task from 8916 children (9-10 years old) to examine Gaussian, ex-Gaussian, and DM indicators of RTV. In addition to describing RTV patterns, we examined interrelations among these indicators, temporal patterns, and sex differences. RESULTS: There was no one-to-one correspondence between DM and ex-Gaussian parameters. Nonetheless, drift rate was most strongly associated with standard deviation of RT and tau, while nondecisional processes were most strongly associated with RT, mu, and sigma. Performance worsened across time with changes driven primarily by decreasing drift rate. Boys were faster and less variable than girls, likely attributable to girls' wide boundary separation. CONCLUSIONS: Intercorrelations among model parameters are similar in children as has been observed in adults. Computational approaches play a crucial role in understanding performance changes over time and can also clarify mechanisms of group differences. For example, standard RT models may incorrectly suggest slowed processing speed in girls that is actually attributable to other factors.

Cognitive dispersion is elevated in amyloid-positive older adults and associated with regional hypoperfusion.

OBJECTIVE: Cognitive dispersion across neuropsychological measures within a single testing session is a promising marker predictive of cognitive decline and development of Alzheimer's disease (AD). However, little is known regarding brain changes underlying cognitive dispersion, and the association of cognitive dispersion with in vivo AD biomarkers and regional cerebral blood flow (CBF) has received limited study. We therefore examined associations among cognitive dispersion, amyloid-beta (Aß) positivity, and regional CBF among older adults free of dementia. METHOD: One hundred and forty-eight Alzheimer's Disease Neuroimaging Initiative (ADNI) participants underwent neuropsychological testing and neuroimaging. Pulsed arterial spin labeling (ASL) magnetic resonance imaging (MRI) was acquired to quantify CBF. Florbetapir positron emission tomography (PET) imaging determined Aß positivity. RESULTS: Adjusting for age, gender, education, and mean cognitive performance, older adults who were Aß+ showed higher cognitive dispersion relative to those who were Aß-. Across the entire sample, higher cognitive dispersion was associated with reduced CBF in inferior parietal and temporal regions. Secondary analyses stratified by Aß status demonstrated that higher cognitive dispersion was associated with reduced CBF among Aß+ individuals but not among those who were Aß-. CONCLUSIONS: Cognitive dispersion may be sensitive to early Aß accumulation and cerebrovascular changes adjusting for demographics and mean neuropsychological performance. Associations between cognitive dispersion and CBF were observed among Aß+ individuals, suggesting that cognitive dispersion may be a marker of brain changes among individuals on the AD continuum. Future studies should examine whether cognitive dispersion predicts brain changes in diverse samples and among those with greater vascular risk burden.

Intraindividual pain variability metrics for youth with sickle cell disease: Relations to health outcomes.

BACKGROUND: While the majority of pediatric sickle cell disease (SCD) research has used mean pain intensity as the only pain metric, recent evidence suggests this metric alone is inadequate in describing the intraindividual variability in SCD pain experiences and subsequent impact. There is limited information on other intraindividual pain metrics in youth with SCD, or how they relate to health outcomes in this population. The aims of this study were to describe differing patterns of intraindividual pain metrics derived from ecological momentary assessments (EMAs) of youth with SCD and to characterize the unique relationships between these metrics and health outcomes. METHODS: Eighty-eight youth with SCD, aged 8-17 (mean age = 11.6), were recruited from three regional pediatric SCD clinics in the United States. At baseline, youth and their guardians reported on demographic and disease information. Then youth completed twice daily EMAs for up to 4 weeks. Pain metrics derived from EMA data were calculated including mean daily pain intensity (DP), SD-DP (standard deviation of DP), proportion of pain days (PPD), and 90th percentile of DP (p90). Pearson correlations were calculated between pain metrics and health outcomes. RESULTS: High DP and SD-DP were correlated with more anxiety symptoms, while high SD-DP and p90 were correlated with more depression symptoms. High SD-DP was correlated with low self-esteem, and high DP and PPD were correlated with low sickle cell self-efficacy. For healthcare utilization due to pain, high p90 was correlated with more emergency department visits, while high DP, p90, and PPD were correlated with more healthcare contacts. CONCLUSION: There are distinct associations between pain variability metrics beyond DP and health outcomes. Collectively, the patterns of associations suggest the utility of these pain metrics for determining risk in relation to specific health outcomes for youth with SCD.

Intraindividual variability in brain activation-A novel correlate of obesity risk among female college students.

There are published data describing impairments in the brain function of adolescents or young adults who have a genetic or familial predisposition for obesity. From these descriptions, it is often assumed that the impairments are appropriately captured by a central tendency estimate and therefore consistently detectable. The present study questions this assumption and shows that the variability in brain function over the time course of a cognitive task is a better predictor of familial risk than its central tendency. Sixty-nine female young adults lacking an obese parent and 24 female young adults with an obese parent were compared on the average amplitude and inter-trial variability (ITV) in amplitude of their P300 electroencephalographic responses to rarely-occurring stimuli during a selective attention task. Simple group comparisons revealed statistically significant findings with effect sizes that were markedly greater for analyses of P300 ITV versus P300 average amplitude. It is suggested that the elevation in P300 ITV among young adults with familial risk indicates temporal instability in systems responsible for the maintenance of attention. These fluctuations may episodically disrupt their attention to satiety cues as well as other cues that influence behavior regulation.

Examining the role of attentional allocation in working memory precision with pupillometry in children and adults.

Working memory (WM) precision, or the fidelity with which items can be remembered, is an important aspect of WM capacity that increases over childhood. Why individuals are more or less precise from moment to moment and why WM becomes more stable with age are not yet fully understood. Here, we examined the role of attentional allocation in visual WM precision in children aged 8 to 13 years and young adults aged 18 to 27 years, as measured by fluctuations in pupil dilation during stimulus encoding and maintenance. Using mixed models, we examined intraindividual links between change in pupil diameter and WM precision across trials and the role of developmental differences in these associations. Through probabilistic modeling of error distributions and the inclusion of a visuomotor control task, we isolated mnemonic precision from other cognitive processes. We found an age-related increase in mnemonic precision that was independent of guessing behavior, serial position effects, fatigue or loss of motivation across the experiment, and visuomotor processes. Trial-by-trial analyses showed that trials with smaller changes in pupil diameter during encoding and maintenance predicted more precise responses than trials with larger changes in pupil diameter within individuals. At encoding, this relationship was stronger for older participants. Furthermore, the pupil-performance coupling grew across the delay period-particularly or exclusively for adults. These results suggest a functional link between pupil fluctuations and WM precision that grows over development; visual details may be stored more faithfully when attention is allocated efficiently to a sequence of objects at encoding and throughout a delay period.

Associations between intraindividual reaction time variability and prospective memory performance in patients with schizophrenia and healthy controls.

Introduction: Patients with schizophrenia exhibit prospective memory (PM) impairment. Intraindividual reaction time variability (IIRTV) is an index of attentional control that is required for PM. This study examined the differences in IIRTV between patients with schizophrenia and healthy controls and the relationship between IIRTV and PM performance.Method: Thirty-nine patients with schizophrenia and forty-two healthy controls were recruited to complete a PM task and the Sustained Attention to Response Task. IIRTV was calculated as the coefficient of variation (mean/SD) of reaction time over correctly responded trials in these tasks.Results: Patients with schizophrenia showed lower PM accuracy and increased IIRTV, while the associations between PM accuracy and IIRTV were significant in healthy controls but not in patients with schizophrenia.Conclusion: These findings suggest impaired PM and relationship between PM and attentional control in patients with schizophrenia.

Negative emodiversity is associated with emotional eating in adolescents: An examination of emotion dynamics in daily life.

INTRODUCTION: Emotional eating is a mental health concern, common in adolescents, that develops as a result of their tendency to use high-energy food to regulate their fluctuating emotions. Due to their highly fluctuating emotional life, adolescents tend to have unique within-person profiles of emotional experiences that change across moments and days, often lost in global assessments of emotions. Hence, it is imperative to examine individual differences in dynamics of emotions, as experienced in daily life, in relation to emotional eating in adolescents. METHODS: In an Ecological Momentary Assessment study, we examined individual differences in three within-person dynamic characteristics (baseline levels, intraindividual variability, and emodiversity) of emotions in 158 dominantly Hispanic adolescents in the United States, aged 14-17 years old, predicting trait-level emotional eating. RESULTS: Results indicated that higher negative emodiversity, baselines, and variability in stress were predictive of emotional eating in adolescents. When all considered together, negative emodiversity (i.e., variety of the types of negative emotions experienced in one's daily life) remained the only significant predictor of emotional eating. CONCLUSIONS: This study affirms the importance of diversity in emotional experiences in relation to emotional eating, particularly in daily contexts of adolescents' lives. Additionally, the study emphasizes the importance of distinguishing between diversity (i.e., variety in types) in positive versus negative emotional experiences with regard to emotional eating. By taking into account the ecological validity of adolescents' daily lives and individual differences in dynamical changes in emotions, we are taking a step forward by shedding light on how the dynamics of negative emotions-in terms of within-person baselines, variability, and diversity-might be related to general levels of emotional eating in adolescents.

Intraindividual variability and emotional change as predictors of sudden gains in imagery rescripting and EMDR for PTSD in adult survivors of childhood abuse.

Sudden gains, defined as large and stable improvements in symptom severity during psychological treatment, have consistently been found to be associated with better outcomes across treatments and diagnoses. Yet, insights on coherent predictors of sudden gains and on emotional changes around sudden gains in post-traumatic stress disorder (PTSD) are lacking. We aimed at replicating a measure of intraindividual variability as a predictor for sudden gains and testing its independence from change during treatment. Furthermore, we expected changes in emotions of guilt, shame and disgust prior to sudden gains to predict sudden gains. Data from a pre-registered randomized controlled trial (RCT) of eye-movement desensitization and reprocessing (emdr) and Imagery Rescripting (ImRs) for PTSD in 155 adult survivors of childhood abuse were used. Intraindividual variability of PTSD symptoms in both treatments did not predict sudden gains status and was not independent of change during treatment. In the EMDR condition, levels of shame during treatment predicted sudden gains and shame decreased shortly before a sudden gain in both treatments. Reductions in all emotions during sudden gains were significantly higher for participants with sudden gains than for comparable intervals in non-sudden gainers. Our findings do not support the predictive validity of intraindividual variability for sudden gains. The decrease of guilt, shame and disgust during sudden gains warrants further research on their role as a mechanism of treatment change for PTSD.

How much does sleep vary from night-to-night? A quantitative summary of intraindividual variability in sleep by age, gender, and racial/ethnic identity across eight-pooled datasets.

Habitual sleep duration and efficiency vary widely by age, gender, and racial/ethnic identity. Despite growing research on the importance of night-to-night, intraindividual variability (IIV) in sleep, few studies have examined demographic differences in sleep IIV. The present study describes typical sleep IIV overall and by demographics among healthy sleepers. Eight datasets of healthy sleepers (N = 2,404; 26,121 total days of sleep data) were synthesised to examine age, gender, and racial/ethnic identity differences in sleep IIV measured via diaries, actigraphy, and electroencephalography (EEG). Sleep IIV estimates included the intraindividual standard deviation (iSD), root mean square of successive differences (RMSSD), coefficient of variation (CV), and a validated Bayesian Variability Model (BVM). There was substantial IIV in sleep across measurement types (diary, actigraphy, EEG) for both sleep duration (iSD: 85.80 [diary], 77.41 [actigraphy], 67.04 [EEG] minutes; RMSSD: 118.91, 108.89, 91.93 minutes; CV: 19.19%, 19.11%, 18.57%; BVM: 60.60, 58.20, 48.60 minutes) and sleep efficiency (iSD: 5.18% [diary], 5.22% [actigraphy], 6.46% [EEG]; RMSSD: 7.01%, 7.08%, 8.44%; CV: 5.80%, 6.27%, 8.14%; BVM: 3.40%, 3.58%, 4.16%). Younger adults had more diary and actigraphy sleep duration IIV. Gender differences were inconsistent. White and non-Hispanic/Latinx adults had less IIV in sleep duration and efficiency compared to racial/ethnic minority groups. Even among healthy sleepers, sleep varies widely from night-to-night. Like mean sleep, there also may be disparities in IIV in sleep by demographic characteristics. Study results help characterise normative values of sleep IIV in healthy sleepers.

WiSER: Robust and scalable estimation and inference of within-subject variances from intensive longitudinal data.

The availability of vast amounts of longitudinal data from electronic health records (EHRs) and personal wearable devices opens the door to numerous new research questions. In many studies, individual variability of a longitudinal outcome is as important as the mean. Blood pressure fluctuations, glycemic variations, and mood swings are prime examples where it is critical to identify factors that affect the within-individual variability. We propose a scalable method, within-subject variance estimator by robust regression (WiSER), for the estimation and inference of the effects of both time-varying and time-invariant predictors on within-subject variance. It is robust against the misspecification of the conditional distribution of responses or the distribution of random effects. It shows similar performance as the correctly specified likelihood methods but is 103 ∼ 105 times faster. The estimation algorithm scales linearly in the total number of observations, making it applicable to massive longitudinal data sets. The effectiveness of WiSER is evaluated in extensive simulation studies. Its broad applicability is illustrated using the accelerometry data from the Women's Health Study and a clinical trial for longitudinal diabetes care.

Altered brain activation in uncomplicated pediatric obesity: The second moment is more sensitive than the first.

Traditionally, studies of the neurocognitive correlates of obesity have computed a central tendency across trials of a task to estimate the functional abilities of individual members of obese and non-obese groups. This computation assumes that the correlate is stable over time-a questionable assumption when individuals are impulsive, periodically inattentive, and capable of overcompensation following awareness of failure. The present investigation departs from the tradition by focusing on the second moment, or variability, in brain activation during a simple selective attention task. It compared 124 non-obese and 80 obese teenaged girls on the across-trial average amplitude and inter-trial variability (ITV) of a sensitive biomarker of attention, the P300 event-related electroencephalographic potential. It found that P300 ITV outperformed P300 average amplitude in differentiating the groups. Further, it found that the elevated P300 ITV among obese teenagers was associated with other indicators of impulsivity and inattention as well as slower reaction times and a trend toward more variable reaction times. Future studies should investigate the value of P300 ITV as an objective and sensitive endpoint for cognitive training focused on improving the attention skills of obese children.

Deviations from typical paths: a novel approach to working with GPS data in the behavioral sciences.

BACKGROUND: Behavioral science researchers are increasingly collecting detailed location data such as second-by-second GPS tracking on participants due to increased ease and affordability. While intraindividual variability has been discussed in the travel literature for decades, traditional methods designed for studying individual differences in central tendencies limit the extent to which novel questions about variability in lived experiences can be answered. Thus, new methods of quantifying behavior that focus on intraindividual variability are needed to address the context in which the behavior occurs and the location tracking data from which behavior is derived. METHODS: We propose deviations from typical paths as a data processing technique to separate individual-level typical travel behavior from a location tracking data set in order to highlight atypical travel behavior as an outcome measure. RESULTS: A simulated data example shows how the method works to produce deviation measures from a location dataset. Analysis of these deviations offers additional insights compared to traditional measures of maximum daily distance from home. CONCLUSIONS: This process can be integrated into larger research questions to explore predictors of atypical behavior and potential mechanisms of behavior change.

How acute affect dynamics impact longitudinal changes in physical activity among children.

Research examined how acute affect dynamics, including stability and context-dependency, contribute to changes in children's physical activity levels as they transition from late-childhood to early-adolescence. Children (N = 151) (ages 8-12 years at baseline) participated in an ecological momentary assessment and accelerometry study with six semi-annual bursts (7 days each) across three years. A two-stage mixed-effects multiple location-scale model tested random intercept, variance, and slope estimates for positive affect as predictors of moderate-to-vigorous physical activity (MVPA). Multi-year declines in MVPA were greater for children who had greater subject-level variance in positive affect. Children who experienced more positive affect when alone did not experience steeper declines in physical activity. Interventions aiming for long-term modifications in children's physical activity may focus on buffering the effects of within-day fluctuations in affect or tailoring programs to fit the needs of "acute dynamic process phenotypes."

Individual dynamics of delta-beta coupling: using a multilevel framework to examine inter- and intraindividual differences in relation to social anxiety and behavioral inhibition.

BACKGROUND: Variation in EEG-derived delta-beta coupling has recently emerged as a potential neural marker of emotion regulation, providing a novel and noninvasive method for assessing a risk factor for anxiety. However, our understanding of delta-beta coupling has been limited to group-level comparisons, which provide limited information about an individual's neural dynamics. METHODS: The present study used multilevel modeling to map second-by-second coupling patterns between delta and beta power. Specifically, we examined how inter- and intraindividual delta-beta coupling patterns changed as a function of social anxiety symptoms and temperamental behavioral inhibition (BI). RESULTS: We found that stronger inter- and intraindividual delta-beta coupling were both associated with social anxiety. In contrast, the high-BI group showed weaker coupling relative to the non-BI group, a pattern that did not emerge when analyzing continuous scores of BI. CONCLUSIONS: In characterizing inter- and intraindividual coupling across the sample, we illustrate the utility of examining neural processes across levels of analysis in relation to psychopathology to create multilevel assessments of functioning and risk.

Mean Levels and Variability in Psychological Well-Being and Associations With Sleep in Midlife and Older Women.

BACKGROUND: Disturbed sleep is prevalent in older adulthood and particularly among women. Greater psychological well-being (PWB) is associated with better sleep, but intraindividual variability in PWB has not been examined. PURPOSE: The current study examined whether mean levels and variability in PWB were associated with sleep disturbances in midlife and older women. METHODS: Participants (N = 189) completed up to seven daily diaries and an end of the week assessment every 3 months for nine waves. Participants answered questions about their nightly sleep disturbances and reported their PWB using Ryff's six dimensions of PWB. RESULTS: Regression models indicated that greater variability in one aspect of PWB, positive relations with others, was related to greater sleep disturbance even after adjusting for mean levels of well-being. Greater variability in environmental mastery, purpose in life, and self-acceptance were also associated with sleep disturbance, but these associations were no longer significant after adjusting for mean levels of well-being. CONCLUSIONS: Results suggest that fluctuations in positive relations with others are related to sleep in adult women above and beyond mean levels of well-being. Results highlight the importance of considering variability in addition to mean levels of PWB.