Adjusting for Baseline Measurements of the Mediators and Outcome as a First Step Toward Eliminating Confounding Biases in Mediation Analysis

The relationship between dissociation and panic symptoms in adolescence and the exploration of potential mediators

Background

Dissociative experiences have been linked to panic symptoms in adolescents, yet the nature of the association remains unclear.

Methods

In the present study, we investigated the longitudinal relationship between dissociative experiences (focusing on the felt sense of anomaly subtype) and panic, as well as the potential mediating roles of emotion regulation strategies (expressive suppression and cognitive reappraisal), alexithymia, and cognitive appraisals of dissociation. Four thousand five hundred one adolescents aged 13-18 years were recruited via social media advertising to take part in an online survey at two timepoints, 1 month apart.

Results

Analysis of 421 datasets found a significant positive relationship between initial dissociative experiences and panic symptoms reported 1 month later. This was mediated by the emotion regulation strategy of cognitive reappraisal, and cognitive appraisals of dissociation. These two variables were no longer significant mediators when controlling for panic symptoms at the first time point, likely due to the stability of panic symptoms across both assessments. Neither alexithymia nor expressive suppression were significant mediators.

Conclusions

Thus, dissociative experiences that are persistently misinterpreted in a catastrophic manner may lead to escalating anxiety and panic symptoms, which could in turn heighten and maintain the feared dissociation sensation. These results indicate that dissociative experiences are associated with panic symptoms in adolescence, with cognitive appraisals of dissociation and cognitive reappraisal playing a role in this relationship.

Beyond mediators: A critical review and methodological path forward for studying mechanisms in alcohol use treatment research

Understanding how treatments for alcohol use disorder (AUD) facilitate behavior change has long been recognized as an important area of research for advancing clinical care. However, despite decades of research, the specific mechanisms of change for most AUD treatments remain largely unknown because most prior work in the field has focused only on statistical mediation. Statistical mediation is a necessary but not sufficient condition to establish evidence for a mechanism of change. Mediators are intermediate variables that account statistically for the relationship between independent and dependent variables, whereas mechanisms provide more detailed explanations of how an intervention leads to a desired outcome. Thus, mediators and mechanisms are not equivalent. To advance mechanisms of behavior change research, in this critical review we provide an overview of methodological shortfalls of existing AUD treatment mechanism research and introduce an etiologically informed precision medicine approach that facilitates the testing of mechanisms of behavior change rather than treatment mediators. We propose a framework for studying mechanisms in alcohol treatment research that promises to facilitate our understanding of behavior change and precision medicine (i.e., for whom a given mechanism of behavior change operates and under what conditions). The framework presented in this review has several overarching goals, one of which is to provide a methodological roadmap for testing AUD recovery mechanisms. We provide two examples of our framework, one pharmacological and one behavioral, to facilitate future efforts to implement this methodological approach to mechanism research. The framework proposed in this critical review facilitates the alignment of AUD treatment mechanism research with current theories of etiologic mechanisms, precision medicine efforts, and cross-disciplinary approaches to testing mechanisms. Although no framework can address all the challenges related to mechanisms research, our goal is to help facilitate a shift toward more rigorous and falsifiable behavior change research.

Association between physical activity and depressive symptoms in adolescents: A prospective cohort study

It remains uncertain whether a protective association between physical activity and depression exists among adolescents and what the optimal level of physical activity might be. This study aimed to estimate the associations of physical activity levels with depressive symptoms and new-onset depression, while identifying potential modifying factors influencing the relationships. In this cohort study, we initially enrolled 1957 participants at baseline and followed up with 1738 of them after two years. Our analysis focused on data from 1482 students who provided complete information on both physical activity and depressive symptoms. Generalized linear regression and restricted cubic spline regression models were performed. Our adjusted models revealed that engaging in 4-7 h/week of moderate-to-vigorous physical activity (MVPA) at baseline was negatively associated with subsequent depressive symptoms and new-onset depression compared to the non-MVPA group. However, exceeding 7 h/week of MVPA did not provide substantial benefits. Furthermore, drinking and screen time potentially modified the relationship between MVPA and new-onset depression. Our findings suggest that 4-7 h of MVPA per week may be an appropriate level to reduce depressive symptoms in adolescents. Moreover, individual behaviors (e.g., drinking and screen time) warrant heightened attention in interventions targeting the reduction of depression in this population.

Mediation of the Association Between Vascular Risk Factors and Depressive Symptoms by C-Reactive Protein

Background

This study examined whether C-reactive protein (CRP), a marker of low-grade systemic inflammation, mediates the association between vascular risk factor (VRF) burden and depressive symptoms.

Methods

We drew on the prospective design of the UK Biobank to include participants with longitudinal data on VRF burden, CRP, and depressive symptoms. Total, direct, and indirect effects were estimated using regression-based mediation models while controlling for confounding by sociodemographic factors, baseline CRP, and baseline depression. Sensitivity analyses probed the robustness of results to unmeasured confounding.

Results

We analyzed data from 10,470 participants from the UK Biobank (mean age = 56.75 years at baseline). Net of covariates, VRFs at baseline were associated with higher depressive symptoms at follow-up (total effect = 0.099; 95% CI, 0.002-0.163). CRP mediated this association (indirect effect = 0.010; 95% CI, 0.004-0.017), accounting for 10.0% (95% CI, 0.3%-30.0%) of the total effect of VRF burden on depressive symptoms. Exploratory analyses suggested that the total and indirect effects pertained to somatic depressive symptoms (tiredness and appetite).

Conclusions

These results suggest that inflammation-promoting effects of VRFs may contribute to depressive symptoms in mid- and later life. However, the mediating pathway via CRP explains only a small part of the association between VRFs and depression after accounting for important covariates and may pertain to specific depressive symptoms. Future studies leveraging similar longitudinal designs are needed to further disentangle the time-varying effects between VRFs, inflammation, and certain depressive symptoms while addressing important confounders.

Effect of Cognitive Behavioral Therapy for Insomnia on Alcohol Treatment Outcomes Among US Veterans: A Randomized Clinical Trial

Importance

Three of 4 adults in treatment for alcohol use disorder (AUD) report symptoms of insomnia. Yet the first-line treatment for insomnia (cognitive behavioral therapy for insomnia, CBT-I) is often delayed until abstinence is established.

Objective

To test the feasibility, acceptability, and preliminary efficacy of CBT-I among veterans early in their AUD treatment and to examine improvement in insomnia as a mechanism for improvement in alcohol use outcomes.

Design, Setting, and Participants

For this randomized clinical trial, participants were recruited through the Addictions Treatment Program at a Veterans Health Administration hospital between 2019 and 2022. Patients in treatment for AUD were eligible if they met criteria for insomnia disorder and reported alcohol use in the past 2 months at baseline. Follow-up visits occurred posttreatment and at 6 weeks.

Interventions

Participants were randomly assigned to receive 5 weekly sessions of CBT-I or a single session about sleep hygiene (control). Participants were asked to complete sleep diaries for 7 days at each assessment.

Main Outcomes and Measures

Primary outcomes included posttreatment insomnia severity (assessed using the Insomnia Severity Index) and follow-up frequency of any drinking and heavy drinking (4 drinks for women, ≥5 drinks for men; number of days via Timeline Followback) and alcohol-related problems (Short Inventory of Problems). Posttreatment insomnia severity was tested as a mediator of CBT-I effects on alcohol use outcomes at the 6-week follow-up.

Results

The study cohort included 67 veterans with a mean (SD) age of 46.3 years (11.8); 61 (91%) were male and 6 (9%) female. The CBT-I group included 32 participants, and the sleep hygiene control group 35 participants. Of those randomized, 59 (88%) provided posttreatment or follow-up data (31 CBT-I, 28 sleep hygiene). Relative to sleep hygiene, CBT-I participants reported greater decreases in insomnia severity at posttreatment (group × time interaction: -3.70; 95% CI, -6.79 to -0.61) and follow-up (-3.34; 95% CI, -6.46 to -0.23) and greater improvements in sleep efficiency (posttreatment, 8.31; 95% CI, 1.35 to 15.26; follow-up, 18.03; 95% CI, 10.46 to 25.60). They also reported greater decreases in alcohol problems at follow-up (group × time interaction: -0.84; 95% CI, -1.66 to -0.02), and this effect was mediated by posttreatment change in insomnia severity. No group differences emerged for abstinence or heavy-drinking frequency.

Conclusions and Relevance

In this randomized clinical trial, CBT-I outperformed sleep hygiene in reducing insomnia symptoms and alcohol-related problems over time but had no effect on frequency of heavy drinking. CBT-I should be considered a first-line treatment for insomnia, regardless of abstinence.

Trial Registration

ClinicalTrials.gov Identifier: NCT03806491.