Strong epidemiologic evidence from ecologic and individual-level studies in the United States supports the claim that access to firearms substantially increases the risk of dying by suicide, ...homicide, and firearm accidents. Less certain is how well particular interventions work to prevent these deaths and other firearm-related harms. Given the limits of existing data to study firearm violence, and the infeasibility of conducting randomized trials of firearm access, it is important to do the best we can with the data we already have. We argue that falsification strategies are a critical - yet underutilized - component of any such analytic approach. The falsification strategies we focus on are versions of "negative controls" analyses in which we expect an analysis should yield a null causal effect, and thus where not obtaining a null effect estimate raises questions about the assumptions underlying causal interpretation of a study's findings. We illustrate the saliency of this issue today with examples drawn from studies published within the last five years in leading peer-reviewed journals. Collecting rich, high-quality data always takes time, urgent as the need may be. On the other hand, doing better with the data we already have can start right now.
Abstract
Mendelian randomization (MR) is used to answer a variety of epidemiologic questions. One stated advantage of MR is that it estimates a “lifetime effect” of exposure, though this term remains ...vaguely defined. Instrumental variable analysis, on which MR is based, has focused on estimating the effects of point or time-fixed exposures rather than “lifetime effects.” Here we use an empirical example with data from the Rotterdam Study (Rotterdam, the Netherlands, 2009–2013) to demonstrate how confusion can arise when estimating “lifetime effects.” We provide one possible definition of a lifetime effect: the average change in outcome measured at time t when the entire exposure trajectory from conception to time t is shifted by 1 unit. We show that MR only estimates this type of lifetime effect under specific conditions—for example, when the effect of the genetic variants used on exposure does not change over time. Lastly, we simulate the magnitude of bias that would result in realistic scenarios that use genetic variants with effects that change over time. We recommend that investigators in future MR studies carefully consider the effect of interest and how genetic variants whose effects change with time may impact the interpretability and validity of their results.
Late-life depressive symptoms have been extensively studied for their relationship with incident dementia, but have been typically assessed at a single timepoint. Such an approach neglects the course ...of depression, which, given its remitting and relapsing nature, might provide further insights into the complex association of depression with dementia. We therefore repeatedly measured depressive symptoms in a population of adults over a decade to study the subsequent risk of dementia.
Our study was embedded in the Rotterdam Study, a population-based study of adults aged 55 years or older in Rotterdam (Netherlands), ongoing since 1990. The cohort is monitored continuously for major events by data linkage between the study database and general practitioners. We examined a cohort of participants who were free from dementia, but had data for depressive symptoms from at least one examination round in 1993-95, 1997-99, or 2002-04. We assessed depressive symptoms with the validated Dutch version of the Center for Epidemiology Depression Scale (CES-D) and the Hospital Anxiety and Depression Scale-Depression. We used these data to identify 11-year trajectories of depressive symptoms by latent class trajectory modelling. We screened participants for dementia at each examination round and followed up participants for 10 years for incident dementia by latent trajectory from the third examination round to 2014. We calculated hazard ratios (HR) for dementia by assigned trajectory using two Cox proportional hazards models (model 1 adjusted for age and sex only, and model 2 adjusted additionally for APOEɛ4 carrier status, educational level, body-mass index, smoking, alcohol consumption, cognitive score, use of antidepressants, and prevalent disease status at baseline). We repeated the analyses censoring for incident stroke, restricting to Alzheimer's disease as an outcome, and accounting for mortality as a competing risk for dementia.
From 1993-2004, we obtained data for depressive symptoms from at least one examination round for 3325 participants (median age: 74·88 years IQR 70·62-80·06, 1995 60% women). We identified five trajectories of depressive symptoms in these 3325 individuals, characterised by maintained low CES-D scores (low; 2441 73%); moderately high starting scores but then remitting (decreasing; 369 11%); low starting scores, increasing, then remitting (remitting; 170 5%); low starting scores that steadily increased (increasing; 255 8%); and maintained high scores (high; 90 3%). During 26 330 person-years, 434 participants developed incident dementia. Only the trajectory with increasing depressive symptoms was associated with a higher risk of dementia compared with the low depressive symptom trajectory, using model 2 (HR 1·42, 95% CI 1·05-1·94; p=0·024). Additionally, only the increasing trajectory was associated with a higher risk of dementia compared with the low trajectory after censoring for incident stroke (1·58, 1·15-2·16; p=0·0041), restricting to Alzheimer's disease as an outcome (1·44, 1·03-2·02; p=0·034), and accounting for mortality as a competing risk (1·45, 1·06-1·97; p=0·019).
Risk of dementia differed with different courses of depression, which could not be captured by a single assessment of depressive symptoms. The higher risk of dementia only in the increasing trajectory suggests depression might be a prodrome of dementia.
Erasmus Medical Center; ZonMw; the Netherlands Ministry of Education Culture and Science; and the Netherlands Ministry for Health, Welfare and Sports.
Objective: To present estimates of the lifetime prevalence of "DSM-IV" mental disorders with and without severe impairment, their comorbidity across broad classes of disorder, and their ...sociodemographic correlates. Method: The National Comorbidity Survey-Adolescent Supplement NCS-A is a nationally representative face-to-face survey of 10,123 adolescents aged 13 to 18 years in the continental United States. "DSM-IV" mental disorders were assessed using a modified version of the fully structured World Health Organization Composite International Diagnostic Interview. Results: Anxiety disorders were the most common condition (31.9%), followed by behavior disorders (19.1%), mood disorders (14.3%), and substance use disorders (11.4%), with approximately 40% of participants with one class of disorder also meeting criteria for another class of lifetime disorder. The overall prevalence of disorders with severe impairment and/or distress was 22.2% (11.2% with mood disorders, 8.3% with anxiety disorders, and 9.6% behavior disorders). The median age of onset for disorder classes was earliest for anxiety (6 years), followed by 11 years for behavior, 13 years for mood, and 15 years for substance use disorders. Conclusions: These findings provide the first prevalence data on a broad range of mental disorders in a nationally representative sample of U.S. adolescents. Approximately one in every four to five youth in the U.S. meets criteria for a mental disorder with severe impairment across their lifetime. The likelihood that common mental disorders in adults first emerge in childhood and adolescence highlights the need for a transition from the common focus on treatment of U.S. youth to that of prevention and early intervention. (Contains 2 figures and 3 tables.)
Ecological studies support the hypothesis that suicide may be "contagious" (i.e., exposure to suicide may increase the risk of suicide and related outcomes). However, this association has not been ...adequately assessed in prospective studies. We sought to determine the association between exposure to suicide and suicidality outcomes in Canadian youth.
We used baseline information from the Canadian National Longitudinal Survey of Children and Youth between 1998/99 and 2006/07 with follow-up assessments 2 years later. We included all respondents aged 12-17 years in cycles 3-7 with reported measures of exposure to suicide.
We included 8766 youth aged 12-13 years, 7802 aged 14-15 years and 5496 aged 16-17 years. Exposure to a schoolmate's suicide was associated with ideation at baseline among respondents aged 12-13 years (odds ratio OR 5.06, 95% confidence interval CI 3.04-8.40), 14-15 years (OR 2.93, 95% CI 2.02-4.24) and 16-17 years (OR 2.23, 95% CI 1.43-3.48). Such exposure was associated with attempts among respondents aged 12-13 years (OR 4.57, 95% CI 2.39-8.71), 14-15 years (OR 3.99, 95% CI 2.46-6.45) and 16-17 years (OR 3.22, 95% CI 1.62-6.41). Personally knowing someone who died by suicide was associated with suicidality outcomes for all age groups. We also assessed 2-year outcomes among respondents aged 12-15 years: a schoolmate's suicide predicted suicide attempts among participants aged 12-13 years (OR 3.07, 95% CI 1.05-8.96) and 14-15 years (OR 2.72, 95% CI 1.47-5.04). Among those who reported a schoolmate's suicide, personally knowing the decedent did not alter the risk of suicidality.
We found that exposure to suicide predicts suicide ideation and attempts. Our results support school-wide interventions over current targeted interventions, particularly over strategies that target interventions toward children closest to the decedent.
IMPORTANCE: Mendelian randomization (MR) studies use genetic variation associated with modifiable exposures to assess their possible causal relationship with outcomes and aim to reduce potential bias ...from confounding and reverse causation. OBJECTIVE: To develop the STROBE-MR Statement as a stand-alone extension to the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guideline for the reporting of MR studies. DESIGN, SETTING, AND PARTICIPANTS: The development of the STROBE-MR Statement followed the Enhancing the Quality and Transparency of Health Research (EQUATOR) framework guidance and used the STROBE Statement as a starting point to draft a checklist tailored to MR studies. The project was initiated in 2018 by reviewing the literature on the reporting of instrumental variable and MR studies. A group of 17 experts, including MR methodologists, MR study design users, developers of previous reporting guidelines, and journal editors, participated in a workshop in May 2019 to define the scope of the Statement and draft the checklist. The draft checklist was published as a preprint in July 2019 and discussed on the preprint platform, in social media, and at the 4th Mendelian Randomization Conference. The checklist was then revised based on comments, further refined through 2020, and finalized in July 2021. FINDINGS: The STROBE-MR checklist is organized into 6 sections (Title and Abstract, Introduction, Methods, Results, Discussion, and Other Information) and includes 20 main items and 30 subitems. It covers both 1-sample and 2-sample MR studies that assess 1 or multiple exposures and outcomes, and addresses MR studies that follow a genome-wide association study and are reported in the same article. The checklist asks authors to justify why MR is a helpful method to address the study question and state prespecified causal hypotheses. The measurement, quality, and selection of genetic variants must be described and attempts to assess validity of MR-specific assumptions should be well reported. An item on data sharing includes reporting when the data and statistical code required to replicate the analyses can be accessed. CONCLUSIONS AND RELEVANCE: STROBE-MR provides guidelines for reporting MR studies. Improved reporting of these studies could facilitate their evaluation by editors, peer reviewers, researchers, clinicians, and other readers, and enhance the interpretation of their results.
PDF
