During the transition from childhood to adolescence, continued improvement in cognition occurs, including increasing task accuracy and faster processing speed (Akshoomoff et al., 2014; Luna et al., 2015). Several mental health problems also have their onset during these phases of life (Jones, 2013; Merikangas et al., 2010; Paus et al., 2008), and simultaneously, the brain undergoes extensive maturation and reorganisation (Lebel & Deoni, 2018; Norbom et al., 2021). To discern the underlying neurobiology of individual differences in cognitive functioning and risk and protective factors for mental health problems in youth, it is important to increase our understanding of the interplay of cognition, psychopathology, and the brain during development from childhood to adolescence and into adulthood.
The present thesis sought to increase our knowledge of various aspects of cognitive control in development, and how it relates to psychopathology and the brain. Especially the interplay of these three factors is central and is elucidated using different analytical approaches and in two different large, population-based samples spanning the age range 8 to 25 years in three research articles. We have carefully chosen our methodological approaches to robustly assess our research questions.
The thesis consists of an introduction, a presentation of the methods that were used, three individual research papers covering different aspects of the overarching theme, and a general discussion. Briefly, in paper 1, we found a specific association between reaction time variability and attention problems, as well as associations between reaction time variability and regional white matter microstructure in children. In paper 2, we elaborated on this and found reduced evidence accumulation in youth with attention problems, and that the development of this aspect of decision making plays a role in developmental changes in attention problems in youth across sexes. Lastly, in paper 3, we found that overall poor task performance is associated with delayed and attenuated neural processing in adolescents.
In this thesis, reflections and challenges from the project will be discussed, including study design, limitations of the stop-signal task, and challenges related to the employed questionnaire and neuroimaging data. In sum, the current thesis elucidates specific cognitive markers of psychopathology and their neural correlates in youth, while also suggesting cognitive control as a unitary, domain-general concept, which is also reflected in neural electrophysiology. More research is however needed, especially in large, longitudinal studies to replicate and elaborate on the findings.