Rajpreet Chahal

Identifying significant predictors of behavioral outcomes is of great interest in many psychological studies. Lasso regression, as an alternative to stepwise regression for variable selection, has started gaining traction among psychologists. Yet, further investigation is valuable to fully understand its performance across various psychological data conditions. Using a Monte Carlo simulation and an empirical demonstration, we compared Lasso regression to stepwise regression in typical psychological datasets varying in sample size, predictor size, sparsity, and signal-to-noise ratio. We found that: (1) Lasso regression was more accurate in within-sample selection and yielded more consistent out-of-sample prediction accuracy than stepwise regression; (2) Lasso with a harsher shrinkage parameter was more accurate, parsimonious, and robust to sampling variability than the prediction-optimizing Lasso. Finally, we concluded with cautious notes and recommendations in practice on the application of Lasso regression.

Internalizing and externalizing problems that emerge during adolescence differentially increase boys’ and girls’ risk for developing psychiatric disorders. It is not clear, however, whether there are sex differences in the intrinsic functional architecture of the brain that underlie changes in the severity of internalizing and externalizing problems in adolescents. Using resting-state fMRI data and self-reports of behavioral problems obtained from 128 adolescents (73 females; 9–14 years old) at two timepoints, we conducted multivoxel pattern analysis to identify resting-state functional connectivity markers at baseline that predict changes in the severity of internalizing and externalizing problems in boys and girls 2 years later. We found sex-differentiated involvement of the default mode network in changes in internalizing and externalizing problems. Whereas changes in internalizing problems were associated with the dorsal medial subsystem in boys and with the medial temporal subsystem in girls, changes in externalizing problems were predicted by hyperconnectivity between core nodes of the DMN and frontoparietal network in boys and hypoconnectivity between the DMN and affective networks in girls. Our results suggest that different neural mechanisms predict changes in internalizing and externalizing problems in adolescent boys and girls and offer insights concerning mechanisms that underlie sex differences in the expression of psychopathology in adolescence.

Background: Females are at higher risk for developing depression during adolescence than are males, particularly during exposure to stressors like the COVID‐19 pandemic. Examining structural connections between brain regions involved in executive functioning may advance our understanding of sex biases in stress and depression. Here, we examined the role of the cingulum bundle in differentiating trajectories of depressive symptoms in males and females across adolescence and during the pandemic.Methods: In a longitudinal study of 214 youth (121 females; ages 9–13 years at baseline), we examined whether fixel‐based properties of the cingulum bundle at baseline predict changes in females' and males' severity of depressive symptoms across four timepoints (4–7 years) in adolescence, including during the COVID‐19 pandemic. We also tested whether cingulum properties predict self‐reported resilience and stress during the pandemic.Results: Females had lower fiber density and cross‐section (FDC) of the cingulum than did males, a neural pattern that predicted greater increases in depressive symptoms, lower resilience, and higher stress during the COVID‐19 pandemic. Cingulum morphometry predicted changes in depressive trajectories in females, but not in males; specifically, females with lower FDC had significant increases in symptoms throughout adolescence, whereas females with higher cingulum FDC did not. Conversely, males had low, stable depressive symptoms throughout adolescence and higher resilience and lower stress during the pandemic compared to females. Higher cingulum FDC predicted higher resilience and lower stress in both sexes.Conclusions: In adults, the cingulum has been implicated in sex differences in stress reactivity. We show that in adolescents, the cingulum reflects sex differences in reports of stress and resilience that might contribute to the increased risk of stress‐related mood disorders in females. Adolescent females might benefit from cognitive interventions that strengthen the structural properties of the cingulum and increase their perceived resilience during periods of adversity and disruption.

Different dimensions of adversity may affect mental health through distinct neurobiological mechanisms, though current supporting evidence consists largely of cross-sectional associations between threat or deprivation and fronto-limbic circuitry. In this exploratory three-wave longitudinal study spanning ages 9–19 years, we examined the associations between experiences of unpredictability, threat, and deprivation with the development of functional connectivity within and between three brain networks implicated in psychopathology: the salience (SAL), default mode (DMN), and fronto-parietal (FPN) networks, and tested whether network trajectories moderated associations between adversity and changes in internalizing symptoms. Connectivity decreased with age on average; these changes differed by dimension of adversity. Whereas family-level deprivation was associated with lower initial levels and more stability across most networks, unpredictability was associated with stability only in SAL connectivity, and threat was associated with stability in FPN and DMN-SAL connectivity. In youth exposed to higher levels of any adversity, lower initial levels and more stability in connectivity were related to smaller increases in internalizing symptoms. Our findings suggest that whereas deprivation is associated with widespread neurodevelopmental differences in cognitive and emotion processing networks, unpredictability is related selectively to salience detection circuitry. Studies with wider developmental windows should examine whether these neurodevelopmental alterations are adaptive or serve to maintain internalizing symptoms.

Background: Suicidal ideation (SI) typically emerges during adolescence but is challenging to predict. Given the potentially lethal consequences of SI, it is important to identify neurobiological and psychosocial variables explaining the severity of SI in adolescents. Methods: In 106 participants (59 female) recruited from the community, we assessed psychosocial characteristics and obtained resting‐state fMRI data in early adolescence (baseline: aged 9–13 years). Across 250 brain regions, we assessed local graph theory‐based properties of interconnectedness: local efficiency, eigenvector centrality, nodal degree, within‐module z ‐score, and participation coefficient. Four years later (follow‐up: ages 13–19 years), participants self‐reported their SI severity. We used least absolute shrinkage and selection operator (LASSO) regressions to identify a linear combination of psychosocial and brain‐based variables that best explain the severity of SI symptoms at follow‐up. Nested‐cross‐validation yielded model performance statistics for all LASSO models. Results: A combination of psychosocial and brain‐based variables explained subsequent severity of SI ( R ² = .55); the strongest was internalizing and externalizing symptom severity at follow‐up. Follow‐up LASSO regressions of psychosocial‐only and brain‐based‐only variables indicated that psychosocial‐only variables explained 55% of the variance in SI severity; in contrast, brain‐based‐only variables performed worse than the null model. Conclusions: A linear combination of baseline and follow‐up psychosocial variables best explained the severity of SI. Follow‐up analyses indicated that graph theory resting‐state metrics did not increase the prediction of the severity of SI in adolescents. Attending to internalizing and externalizing symptoms is important in early adolescence; resting‐state connectivity properties other than local graph theory metrics might yield a stronger prediction of the severity of SI.

Internalizing symptoms typically emerge in adolescence and are more prevalent in females than in males; in contrast, externalizing symptoms typically emerge in childhood and are more commonly observed in males. Previous research has implicated aspects of white matter organization, including fractional anisotropy (FA), of cerebral tracts in both internalizing and externalizing symptoms. Although the cerebellum has been posited to integrate limbic and cortical regions, its role in psychopathology is not well understood. In this longitudinal study, we investigated whether FA of the superior (SCP), middle (MCP), and inferior cerebellar peduncles (ICP) predict change in symptoms and whether sex moderates this association. One hundred eleven adolescents completed the Youth Self-Report, assessing symptoms at baseline (ages 9–13 years) and again 2 years later. Participants also underwent diffusion-weighted imaging at baseline. We used deterministic tractography to segment and compute mean FA of the cerebellar peduncles. Lower FA of the right SCP at baseline predicted increases in internalizing symptoms in females only. Lower FA in the right SCP and ICP also predicted increases in externalizing symptoms in females, but these associations did not survive multiple comparison correction. There was no association between FA of the cerebellar peduncles and change in symptoms in males or between MCP FA and symptom changes in males or females. Organizational properties of the SCP may be a sex-specific marker of internalizing symptom changes in adolescence. The cerebellar peduncles should be explored further in future studies to elucidate sex differences in symptoms.

Young adults are acutely sensitive to peer influences. Differences have been found in neural sensitivity to explicit peer influences, such as seeing peer ratings on social media. The present study aimed to identify patterns of neural sensitivity to implicit peer influences, which involve more subtle cues that shape preferences and behaviors. Participants were 43 young adults (M_Age = 19.2 years; 24 males) who underwent functional magnetic resonance imaging while completing a task used to assess neural responses to implicitly “socially tagged” symbols (previously judged by peers as liked vs. not liked, thus differing in apparent popularity) vs. novel symbols that carried no social meaning (not judged by peers). Results indicated greater activity in brain regions involved in salience detection (e.g., anterior cingulate cortex) and reward processing (e.g., caudate) to socially tagged vs. novel symbols, and particularly to unpopular symbols. Greater self-reported susceptibility to peer influence was related to more activity in the insula and caudate when viewing socially tagged vs. novel symbols. These results suggest that the brain is sensitive to even subtle cues varying in level of peer endorsement and neural sensitivity differed by the tendency to conform to peers’ behaviors particularly in regions implicated in social motivation.