Twice as many women as men suffer from mood and anxiety disorders, yet the biological underpinnings of this phenomenon have been understudied and remain unclear. We and others have shown that the hemodynamic response to subliminally presented sad or happy faces during functional MRI (fMRI) is a robust biomarker for the attentional bias toward negative information classically observed in major depression. Here we used fMRI to compare the performance of healthy females (n = 28) and healthy males (n = 28) on a backward masking task using a fast event‐related design with gradient‐recalled, echoplanar imaging with sensitivity encoding. The image data were compared across groups using a region‐of‐interest analysis with small‐volume correction to control for multiple testing ( P corrected < 0.05, cluster size ≥ 20 voxels). Notably, compared with males, females showed greater BOLD activity in the subgenual anterior cingulate cortex (sgACC) and the right hippocampus when viewing masked sad vs. masked happy faces. Furthermore, females displayed reduced BOLD activity in the right pregenual ACC and left amygdala when viewing masked happy vs. masked neutral faces. Given that we have previously reported similar findings for depressed participants compared with healthy controls (regardless of gender), our results raise the possibility that on average healthy females show subtle emotional processing biases that conceivably reflect a subgroup of women predisposed to depression. Nevertheless, we note that the differences between males and females were small and derived from region‐of‐interest rather than voxelwise analyses. © 2016 Wiley Periodicals, Inc.

Females are more vulnerable than men to developing stress‐related disorders such as posttraumatic stress disorder and general anxiety disorder (McLean and Anderson, 2009; Kessler et al., 2012), and the lifetime rate of major depressive disorder (MDD) in women has consistently been found to be twice that of men (Kessler et al., 1994; Kessler, 2003). Healthy females also experience more negative emotions (Else‐Quest et al., 2012), show superior recall of emotional memories (Cahill, 2003), and are more sensitive than males to the corporeal manifestations of emotion, including facial expressions (Hall and Matsumoto, 2004; Kret and De Gelder, 2012). However, it is not yet clear whether these phenomena are related to the epidemiological differences between the sexes in mood and anxiety disorders. What is known is that 1) early‐life stress is a potent risk factor for the development of major depression (Kendler et al., 2004; Kessler, 1997); 2) the neural circuits involved in stress are some of the most sexually dimorphic regions in the brain (Goldstein et al., 2001); 3) disruption of the hypothalamic‐pituitary‐adrenal (HPA) axis during development in rodents has sex‐specific effects on the hypothalamus, amygdala, hippocampus, and medial prefrontal cortex (mPFC) that compromise stress regulation in adulthood (Goldstein et al., 2014); and 4) gonadal hormones also regulate affective responses via the HPA circuitry in healthy human adults (van Wingen et al., 2008, 2009; Petersen and Cahill, 2015). Consistent with these data, several functional neuroimaging studies have identified sex differences in the magnitude of corticolimbic responses to different types of emotional stimuli. A recent meta‐analysis of these studies revealed that, compared with the case in healthy men, negatively valenced emotional stimuli of all types elicit greater activation of corticolimbic circuits in healthy women including, the left amygdala, left medial‐dorsal thalamus, left anterior cingulate, and mPFC (Stevens and Hamann, 2012). Moreover, compared with healthy women, men displayed greater activity of several brain regions, most notably the subcallosal gyrus, inferior frontal gyrus, and left amygdala in response to positive stimuli (Stevens and Hamann, 2012). Volume reductions, altered neural activity, and/or altered functional connectivity of components of the stress neurocircuitry are widely reported in the depression literature (Savitz and Drevets, 2009a, 2009b; Price and Drevets, 2012; Hamilton et al., 2015). Furthermore, these structural and functional abnormalities are linked to behavioral abnormalities, notably a fundamental mood‐congruent processing bias characteristic of depression; i.e., a greater sensitivity to negative stimuli coupled with reduced attention to and memory for positive, socially relevant stimuli (Harmer et al., 2004; Joormann and Gotlib, 2007; Disner et al., 2011). For example, depressed patients display exaggerated BOLD responses in the amygdala to explicitly presented sad faces (Siegle et al., 2002; Surguladze et al., 2005), and this abnormality is normalized after treatment with antidepressant medication (Fu et al., 2004; Arnone et al., 2012). We (Victor et al., 2010, 2013) and others (Sheline et al., 2001; Suslow et al., 2010; Stuhrmann et al., 2013) have developed a sensitive and reliable probe of the neural correlates of automatic or nonconscious emotional processing biases, i.e., a backward masking fMRI paradigm in which combinations of neutral, sad, and happy faces are displayed in pairs with the first face displaced (masked) by a second face after 17–30 msec so that the participant is consciously aware only of viewing the second face. The advantage of the subliminal presentation of the faces is that they may help to divorce the automatic, early processes underpinning attentional bias from more elaborate conscious processes such as empathy or negative ruminations, which may be less reflective of the underlying neurobiology. We have demonstrated the existence of a “double dissociation” in which, relative to healthy controls, depressed participants on average display increased BOLD responses in the amygdala to sad faces but decreased BOLD responses in the amygdala to masked happy faces (Victor et al., 2010). This effect was reversed by treatment with a selective serotonin reuptake inhibitor (SSRI; Victor et al., 2010), consistent with other reports in the literature (Sheline et al., 2001). Subsequently, we reported depression‐associated changes in an extended anatomical network, for instance, greater activity to masked sad vs. masked happy faces in the left hippocampus and greater activity to masked sad vs. masked neutral faces in the left superior temporal cortex and right orbitofrontal cortex (Victor et al., 2012). Notably, we also reported that, at baseline, MDD patients displayed an increased hemodynamic response to masked sad vs. masked happy faces in the pregenual ACC (pgACC), an effect that was reversed by 8 weeks of treatment with the SSRI sertraline (Victor et al., 2013). In summary, it has been previously hypothesized that increased female sensitivity to negative emotional stimuli partially explains the greater prevalence of depression and anxiety disorders among women (Leach et al., 2008; Nolen‐Hoeksema, 2012). There is indirect evidence to support this hypothesis: 1) healthy women respond more strongly than healthy men to negative emotional stimuli, 2) depressed individuals show a negative emotional processing bias, and 3) there is a degree of correspondence in the neural response to emotionally valenced stimuli (e.g., faces) in healthy women vs. men to those in depressed individuals vs. healthy controls. Nevertheless, 1) only modest numbers of studies have explicitly compared the neural activity between men and women during fMRI scanning with affective paradigms, 2) the implications of these studies are not completely clear because not all of the tasks employed in previous studies have been demonstrated to differentiate depressed from healthy participants robustly, and 3) to our knowledge the neural correlates of sex differences to subliminally processed masked sad and happy faces have not been studied in healthy individuals. Here we compare the neurophysiological responses of healthy men and women on the backward masking task, a sensitive and reliable probe of a nonconscious emotional processing bias that is salient in depression. We hypothesized that, relative to healthy males, healthy females would show similarities to patients with depression, i.e., greater BOLD activity to sad vs. happy faces in the amygdala, hippocampus, and pgACC.

MATERIALS AND METHODS Participants All participants were recruited from the Laureate Psychiatric Clinic and Hospital (LPCH) or the general community through radio and print advertisements. Participants provided written informed consent after receiving a full explanation of the study procedures and risks as approved by the local IRB. Participants (n = 56; 50% female, ages 18–55 years) were interviewed with the Structured Clinical Interview for the DSM‐IV‐TR (First et al., 2002), and additionally completed the Hamilton Depression Rating Scale (HDRS, 25‐item) in order to exclude volunteers with psychiatric disorders. Volunteers were excluded if they had either a personal or a family history (in first‐degree relatives) of major psychiatric disorders according to the Family Interview for Genetic Studies (Maxwell, 1992). Additional exclusion criteria included medical conditions or concomitant medications likely to influence CNS function, including cardiovascular, respiratory, endocrine, and neurological diseases, and general MRI exclusions such as paramagnetic implants or claustrophobia. In accordance with previously published work (Maki et al., 2002; Petersen et al., 2014), females were divided into two principal groups for post hoc exploratory analyses: early follicular phase (days 1–6; low estrogen/progesterone, n = 8) and midluteal phase (days 18–24; high estrogen/progesterone, n = 6). Individuals who did not fall into these groups were labeled as “other” (oral contraceptives, n = 2; hysterectomy, n = 2; different phase, n = 10; total n = 14). fMRI Task and Processing fMRI scanning was performed on a 3‐T GE MR750 MRI scanner with an eight‐channel receive‐only head coil. Gradient‐recalled, echoplanar imaging (EPI) with sensitivity encoding (SENSE) was used for fMRI with the following parameters: repetition/echo times (TR/TE) = 2,000/27 msec, SENSE acceleration = 2, flip angle = 90°, matrix = 96 × 96, field‐of‐view (FOV) = 24 cm, 39 axial slices, voxel size = 2.5 × 2.5 × 2.9 mm3. The first three imaging volumes of each run were discarded to allow for steady‐state tissue magnetization. High‐resolution T1‐weighted anatomical MRI scans (TR/TE = 6/2.1 msec, prep/delay = 725/1,400 msec, FOV 240 × 192 mm, delay = 1,400 msec, flip angle = 8°, SENSE acceleration = 2, 186 axial slices, voxel size = 0.94 × 0.94 × 0.9 mm) were acquired for coregistration with the EPI series. Prior to each of two 9‐min, 8‐sec runs, participants were shown two neutral target faces and instructed to remember the faces for the next scan run and respond as quickly as possible to indicate if the presented face matched one of the target faces based on identity (not emotional expression). Two faces were presented for each stimulus, a “masked” face for 26 msec, immediately followed by a “masking face” for 107 msec, and a fixation cross for 1,866 msec. In total, 48 stimuli [six combinations: (sad/neutral, happy/neutral, neutral/sad, neutral/happy, neutral/neutral female, neutral/neutral male) × 8 presentations each] were presented in each run in a pseudorandomized, mixed‐trial design, with the emotional pairings predetermined (e.g., happy/neutral), and the program Optseq (Dale, 1999) was used to determine the order of face presentation randomly, with an equal number of target faces presented in each position. Each event type was gender matched. Two different stimulus face sets equivalent on ratings of valence were counterbalanced and used for the two runs. Faces were selected from the NimStim Set of Facial Expressions (Tottenham et al., 2009). A 2–6‐sec interstimulus interval served as a baseline comparison. Image preprocessing and analysis were performed via AFNI (http://afni.nimh.nih.gov) and comprised despiking, slice acquisition time correction, and within‐subject realignment. The anatomical image was registered to the first functional image then spatially normalized to the TT_N27 template with Advanced Normalization Tools (ANTs) with the SyN method (Avants et al., 2008). The estimated warping parameter was used to normalize the functional images. The template image was resampled to 1.75‐mm3 isotropic voxels so that the spatially normalized image had a voxel size of 1.75 mm3. Images were smoothed using a 4‐mm full‐width half‐maximum Gaussian kernel, and the signal time course was scaled to percentage signal change relative to the mean signal across time in each voxel. By using 3dDeconvolve for each participant, the hemodynamic response to each event type was modeled with a delta function at the event onset and convolved with the gamma‐variate hemodynamic response function. Regressors modeling the task, motion parameters, and fourth‐order polynomial regressors were used in the model. Because the masked and unmasked faces for each stimulus pair were presented too closely in time to model the response to each component separately, the data were modeled as event‐related correlates of the combined stimulus pairs; these pairs were the main effects of interest: presentation of sad/neutral (SN), happy/neutral (HN), and neutral/neutral (NN) faces. Events with target faces of sad and happy in the unmasked position were also modeled separately and included in the design matrix. Regions‐of‐interest were defined using the Talairach masks provided within AFNI for the amygdala and hippocampus. A modified AFNI mask was used to define the region making up the perigenual ACC. For each participant, the 3dDeconvolve output was resampled and the masks applied to calculate the percentage signal change within the regions‐of‐interest for the SN‐HN, SN‐NN, and HN‐NN contrasts. The significance threshold was set at P < 0.05 after small‐volume correction with a cluster size ≥ 20. For each individual, the resulting percentage signal change values (beta‐weights) over the peak voxels of clusters of interest were extracted and used to test for differences across menstrual phase and correlations with depression scores using ANOVA and Pearson's correlation coefficient, respectively, as implemented in SPSS v17.

RESULTS Males and females did not differ significantly in age (31 ± 10 vs. 34 ± 10 years) or HDRS score (0.6 ± 1.2 vs. 0.6 ± 0.9). Furthermore, there was no group difference in self‐reported childhood trauma, anxiety, or personality traits (see Table I). Table I. Demographic Data and Psychometric Differences Between Males and Females Male Female Statistic N 28 28 Age (years) 30.2 ± 10.6 34.1 ± 9.6 t 54 = 1.5, P = 0.152 HDRS 0.6 ± 1.5 0.6 ± 0.9 t 54 = 0.1, P = 0.914 HAM‐A 0.5 ± 0.9 0.7 ± 1.0 t 53 = 0.8, P = 0.451 STAI‐State 23.7 ± 3.6 24.5 ± 5.5 t 54 = 0.6, P = 0.530 STAI‐Trait 25.6 ± 4.6 26.8 ± 5.5 t 54 = 0.9, P = 0.388 TCI‐HA 6.6 ± 5.2 8.1 ± 5.8 t 54 = 1.0, P = 0.313 TCI‐NS 18.0 ± 6.9 15.7 ± 7.6 t 54 = 1.2, P = 0.234 TCI‐P 5.3 ± 2.1 5.2 ± 2.2 t 54 = 0.3, P = 0.803 TCI‐RD 14.8 ± 5.1 15.4 ± 6.5 t 54 = 0.4, P = 0.715 TCI‐Impulsivity 3.0 ± 2.0 2.8 ± 2.2 t 54 = 0.5, P = 0.610 TCI‐C 35.7 ± 7.8 35.2 ± 12.6 t 54 = 0.2, P = 0.849 TCI‐SD 37.4 ± 8.2 35.0 ± 6.8 t 54 = 0.8, P = 0.417 TCI‐ST 11.9 ± 5.8 13.5 ± 6.8 t 54 = 1.0, P = 0.337 CTQ 31.0 ± 10.6 29.6 ± 5.2 t 40 = 0.7, P = 0.501 Relative to males, females showed the following differences in BOLD activity to emotionally valenced faces (Table II, Fig. 1): 1) an increased BOLD response to masked sad vs. masked happy faces (SN‐HN) in the right hippocampus and the bilateral sgACC and 2) a decreased BOLD response to masked happy vs. masked neutral faces (HN‐NN) in the left amygdala (in the vicinity of the central nucleus), the right sgACC (located in the subcallosal gyrus area that putatively corresponds to infralimbic cortex), and the right pgACC. Figure 1 Open in figure viewer PowerPoint Regional differences in hemodynamic response between males and females while viewing emotionally expressive face stimuli presented below the level of conscious awareness using the backward masking task. The clusters of voxels for which P corrected < 0.05 in the fMRI contrasts are superimposed on sagittal or coronal sections from coregistered anatomical MRI images (left column). Adjacent to each image is the corresponding bar graph showing contrast beta‐weights plus standard error bars that correspond to the differences between female and male subjects measured over the peak voxel T value shown in the image data. A and B show the difference in BOLD activity between females and males in response to masked sad vs. masked happy face stimuli (SN‐HN) in the left sgACC (A) and right hippocampus (B). C shows the regional difference in BOLD activity between females and males in response to happy vs. neutral face stimuli (HN‐NN) in the left amygdala. Coordinates for the peak T values correspond to the stereotaxic array of Talairach and Tournoux (1988) as the distance in millimeters from the anterior commissure (positive x, right; positive y, anterior; positive z, dorsal). HN‐NN, masked happy vs. masked neutral faces; SN‐HN, masked‐sad vs. masked‐happy faces; sgACC, subgenual anterior cingulate cortex. Table II. Regional Differences in BOLD Response to Emotionally Valenced Faces in Females vs. Males Contrast Region Talairach coordinates X Y Z Cluster size T value SN‐HN F > M L sgACC (BA25) −1 11 −5 25 3.49 F > M R sgACC (BA24) 1 24 −3 26 2.97 F > M R hippocampus 32 −20 −8 23 2.86 HN‐NN F < M L amygdala −25 −13 −8 56 3.73 F < M R sgACC 1 18 −10 27 3.81 F < M R pgACC 11 45 11 24 2.83 There was no significant association between HDRS scores and the magnitude of the regional hemodynamic response measured over the peak voxel within each cluster of significant group difference (N = 56, rs < 0.2, Ps > 0.1). Furthermore, no significant effect of menstrual phase on activation of the amygdala, hippocampus or sgACC was observed in the female group (N = 28, F 2,25 < 2, Ps > 0.1).

DISCUSSION The principal results were that, relative to males, 1) females showed an increased BOLD response in the SN‐HN contrast in the right hippocampus and sgACC bilaterally and 2) females showed a reduced BOLD response in the left amygdala and right sgACC in the HN‐NN contrast. Altered activity of the ventromedial PFC in mood disorders, in particular the region ventral to the genu of the corpus callosum (subcallosal gyrus), is one of the most robust findings in biological psychiatry (Drevets et al., 2008; Savitz and Drevets, 2009a). The subcallosal gyrus comprises cytoarchitectonically distinct anterior and posterior components, termed the sgACC and the infralimbic cortex, which correspond approximately to BA 24 and 25, respectively (Ongur et al., 2003). Increased activity in the subcallosal gyrus as well as the region rostral to the genu (pgACC) has been demonstrated to be associated with negative emotional processing biases in depression (Laxton et al., 2013; Victor et al., 2013). For instance, increased activation of the sgACC in response to sad vs. neutral faces was observed in patients with MDD relative to healthy controls (Gotlib et al., 2005). Conversely, greater BOLD activity in the pgACC in response to happy faces is predictive of remission or response to treatment at followup (Diler et al., 2013; Opmeer et al., 2016). For depressed patients we previously showed a decrease in the hemodynamic response to masked sad vs. masked happy faces following sertraline treatment in the pgACC (Victor et al., 2013). Furthermore, this decrement in pgACC activity cooccurred with a positive shift in the emotional processing bias and a reduction in depressive symptoms (Victor et al., 2013). Consistent with these data, in healthy individuals, engagement of the pgACC during the processing of happy faces is positively correlated with emotional stability (Brassen et al., 2011). The sgACC and the pgACC share substantial, reciprocal anatomical connections with the amygdala (Amaral and Insausti, 1992), which is one of the most sexually dimorphic regions of the brain in both rodents (Hines et al., 1992; Cooke and Woolley, 2005) and in humans (Goldstein et al., 2001). The amygdala not only is activated by negative or aversive stimuli (LeDoux, 2000) but is sensitive to the relative intensity of positive stimuli (Bonnet et al., 2015). However, there also is evidence for the lateralization of amygdalar function in the context of emotional processing. For instance, masked affective stimuli, regardless of valence, are associated with greater activation of the left compared with the right amygdala (Killgore and Yurgelun‐Todd, 2004). Conceivably, the lateralized pattern of amygdalar function is partially related to sex differences reported in the literature. The relative decrease in response to happy faces in the left amygdala in women found here is partially consistent with a report of greater left amygdala activation in men than in women during the viewing of pleasant International Affective Picture System (IAPS) images (Wrase et al., 2003). Furthermore, a recent meta‐analysis reported reduced activation in the left amygdala to a variety of positive emotions in healthy women compared with men (Stevens and Hamann, 2012). In addition, Cahill and colleagues found that in women the left amygdala showed greater functional connectivity with the sgACC and hypothalamus at rest, a result that the authors propose may be relevant to the sex‐related lateralization of amygdalar function in the encoding of emotional memories (Kilpatrick et al., 2006). Further evidence for sex‐dependent lateralization of amygdala function was provided by Buchel and colleagues in their analysis of amygdalar response to neutral and angry faces among adolescents (Schneider et al., 2011). Compared with females, males showed a stronger activation of the right amygdala compared with the left amygdala, and this effect was enhanced when viewing angry faces, suggesting that emotional content enhanced this left–right differential (Schneider et al., 2011). The reduced left amygdalar response to masked happy faces in healthy females vs. males potentially is relevant to understanding the increased prevalence of depression among females. Using a previous iteration of the backward masking task in a fully independent sample of participants, we showed that, compared with healthy controls, age‐ and sex‐matched unmedicated MDD patients displayed a greater automatic amygdala response to sad faces and, conversely, a reduced amygdala response to happy faces; both of these abnormalities relative to healthy controls were normalized by treatment with sertraline (Victor et al., 2010). The same phenomenon of decreased amygdalar response to subliminally presented happy faces among depressed individuals also was reported by Suslow, Dannlowski, and colleagues (Suslow et al., 2010; Stuhrmann et al., 2013). The absence of a “normal” positive processing bias is increasingly recognized as a key trait‐like component of depression. Behavioral or neurophysiological responses to reward have been demonstrated to remain abnormal in remitted patients with MDD (McCabe et al., 2009; Pechtel et al., 2013), and consistent with these data we previously showed a reduced BOLD response in the left amygdala in remitted MDD individuals in the HN‐NN contrast (Victor et al., 2010). Furthermore, several studies have demonstrated that an early increase in positive affect after the initiation of antidepressant treatment is a positive prognostic indicator (Tranter et al., 2009; Geschwind et al., 2011). In fact, Harmer (2008) has proposed that a common effect of antidepressant pharmacotherapy that cuts across different classes of medication is a shift in the emotional processing bias in the positive direction. With regard to the hippocampus, our finding of an increased hemodynamic response to SN‐HN faces in females vs. males (xyz = 32, −20, −8) is noteworthy in light of our previous report of elevated BOLD activity in the SN‐HN contrast in the hippocampus (xyz = −18, −24, −12) in MDD subjects vs. healthy controls (Victor et al., 2012). Hippocampal lesions interrupt afferent neurotransmission to the amygdala, which typically conveys information regarding the broader environmental context (e.g., place or time) of an emotionally salient stimulus (Phillips and LeDoux, 1994). Thus, we previously hypothesized that the hippocampus sets the context for the negative emotional processing bias observed in depression by driving the amygdala to respond differently to sad vs. happy stimuli (Victor et al., 2012). Estradiol plays an important role in regulating hippocampus‐dependent learning and memory under stress by modulating dendritic spine density and synaptic number within the hippocampus (Luine, 2015). For instance, estradiol replacement in ovariectomized rats may increase contextual fear memory formation and decrease fear extinction learning (McDermott et al., 2015), although some studies have reported that blockade of estradiol production impairs rather than enhances fear extinction (Graham and Milad, 2013). Conceivably, estradiol and/or other gonadal hormones may affect hippocampus‐dependent memory formation during emotionally salient events and thus influence the tendency to develop negative (or positive) emotional processing biases. One important limitation of our study is that the reported differences between males and females were relatively small and were derived from region‐of‐interest analyses with a relatively liberal threshold for statistical significance, i.e., P < 0.05 after small volume correction with a minimum cluster size of 20 contiguous voxels. Another important limitation is that our study was likely underpowered to detect neurophysiological differences between women according to the phase of the menstrual cycle. Thus the absence of a significant association between menstrual phase and the hemodynamic response to masked faces in females should be treated with caution because other studies have suggested that estrogen and progesterone may play opposing roles in modulating the brain's stress circuitry (Goldstein et al., 2005; Andreano and Cahill, 2010; Ossewaarde et al., 2010; Petersen et al., 2014). Noteworthy strengths of the methods include the rapid event‐related, backward masking design and the high sensitivity of the imaging methods for regions prone to BOLD signal susceptibility artifact. Compared with the slow‐event related backward masking task that we described earlier (Victor et al., 2010), in the current study we employed a rapid event‐related design, which allowed more trials during a shorter scan time. An advantage of this shorter task is that head motion during scanning is minimized. In addition, the improved imaging hardware, acquisition speed, and BOLD signal sensitivity that we employed here afforded higher temporal signal‐to‐noise ratios than the scanning technology used by Victor et al. (2010), particularly in areas such as the basotemporal and basofrontal cortices. This greater sensitivity may explain our ability to detect BOLD changes during task performance in the subgenual PFC, an area that is susceptible to BOLD signal dropout because of its proximity to the sphenoid sinus. As reported above, Gotlib et al. (2005) previously found activation of the sgACC region in response to sad vs. neutral faces in patients with MDD relative to healthy controls. Moreover, for depressed patients being prepared for deep brain stimulation, Laxton et al. (2013) performed electrophysiological recordings from neurons in the sgACC region and showed that these neurons preferentially responded to emotional pictorial stimuli, with more neurons increasing their firing activity with viewing of affectively negative vs. positive stimuli. The technical improvements implemented here to increase sensitivity to BOLD activity in this region proved advantageous for characterizing sex differences in the neural response of the subgenual PFC region to implicitly presented sad vs. happy faces.

CONFLICT OF INTEREST STATEMENT TAV, MM, JB, and JS have no disclosures. WCD is an employee of Janssen Research & Development, LLC, of Johnson & Johnson.

ROLE OF AUTHORS All authors had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: TAV, WCD, JS. Acquisition of data: TAV, JB. Analysis and interpretation of data: TAV, WCD, MM, JB, JS. Drafting of the manuscript: JS. Critical revision of the manuscript for important intellectual content: TAV, WCD, MM, JB, JS. Statistical analysis: TAV, JS. Obtained funding: WCD, JS. Administrative, technical, and material support: JB, JS. Study supervision: TV, JS.