Editorial

Subclinical Psychiatric Symptoms and the Brain: What Can Developmental Population Neuroimaging Bring to the Table?

Increased intraindividual variability (IIV) in reaction times (RTs) has been suggested as a key cognitive and behavioral marker of attention problems, but findings for other dimensions of psychopathology are less consistent. Moreover, while studies have linked IIV to brain white matter microstructure, large studies testing the robustness of these associations are needed.

We used data from the Adolescent Brain Cognitive Development (ABCD) Study baseline assessment to test the associations between IIV and psychopathology (n = 8622, age = 8.9–11.1 years) and IIV and white matter microstructure (n = 7958, age = 8.9–11.1 years). IIV was investigated using an ex-Gaussian distribution analysis of RTs in correct response go trials in the stop signal task. Psychopathology was measured by the Child Behavior Checklist and a bifactor structural equation model was performed to extract a general p factor and specific factors reflecting internalizing, externalizing, and attention problems. To investigate white matter microstructure, fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity were examined in 23 atlas-based tracts.

Increased IIV in both short and long RTs was positively associated with the specific attention problems factor (Cohen’s d = 0.13 and d = 0.15, respectively). Increased IIV in long RTs was also positively associated with radial diffusivity in the left and right corticospinal tract (both tracts, d = 0.12).

Using a large sample and a data-driven dimensional approach to psychopathology, the results provide novel evidence for a small but specific association between IIV and attention problems in children and support previous findings on the relevance of white matter microstructure for IIV.

Recent years have seen an advent in population-based studies in children, adolescents, and adults that examine the prevalence, etiology, and developmental trajectories of diverse subclinical psychopathological symptoms that pose a risk for the later development of severe mental illnesses. It is increasingly recognized that most categorically defined psychiatric disorders occur on a spectrum or continuum, show high heterogeneity and symptom overlap, and share genetic and environmental risk factors. We discuss neurodevelopmental underpinnings of psychosis spectrum symptoms and review brain morphometric and functional alterations as well as genetic liability for psychosis in individuals experiencing psychotic symptoms (PSs) in the general population. With regard to brain structure and function, findings of qualitatively similar alterations in individuals experiencing subthreshold PSs and individuals with overt psychotic disorders support the notion of a psychosis continuum. However, genetic and epidemiological studies have emphasized the overlap of PSs and other psychiatric illnesses. In particular, PSs during adolescence appear to be a nonspecific precursor of different psychopathological outcomes. Given the evidence presented in this review, we argue that findings from population-based studies are appropriate to guide policy-making to further emphasize public health efforts. Broadly accessible mental health programs are promising to make a difference in the field of adolescent mental health. However, the specific efficacy of these programs warrants further study, and caution is advised to not overpathologize potentially transient occurrence of mental health problems.

Diffusion magnetic resonance imaging (dMRI) continues to grow in popularity as a useful neuroimaging method to study brain development, and longitudinal studies that track the same individuals over time are emerging. Over the last decade, seminal work using dMRI has provided new insights into the development of brain white matter (WM) microstructure, connections and networks throughout childhood and adolescence. This review provides an introduction to dMRI, both diffusion tensor imaging (DTI) and other dMRI models, as well as common acquisition and analysis approaches. We highlight the difficulties associated with ascribing these imaging measurements and their changes over time to specific underlying cellular and molecular events. We also discuss selected methodological challenges that are of particular relevance for studies of development, including critical choices related to image acquisition, image analysis, quality control assessment, and the within-subject and longitudinal reliability of dMRI measurements. Next, we review the exciting progress in the characterization and understanding of brain development that has resulted from dMRI studies in childhood and adolescence, including brief overviews and discussions of studies focusing on sex and individual differences. Finally, we outline future directions that will be beneficial to the field.