Rates of depression and anxiety increase sharply in adolescence, especially in females where instances of first episode depression or anxiety are approximately double that of males1. A single episode of depression or anxiety can lead to enduring negative psychosocial consequences, such as suicidality, addiction, and unemployment2. In addition, an episode can leave the individual vulnerable to further episodes, at which point depression and anxiety can become chronic, treatment-resistant disorders3.
Recent neuroimaging research in internalizing disorders (i.e., depression and anxiety) has aimed to find neural markers of risk in youth, but there is a lack of longitudinal research predicting first episode onset in high-risk youth4,5. This study aims to investigate if functional connectivity between core intrinsic networks previously implicated in internalizing psychopathology could act as a neural marker of premorbid risk for internalizing disorder onset in a longitudinal cohort of youth at high risk, by virtue of having a parent with a history of these disorders. Resting state functional connectivity (RSFC) is assessed via the temporal correlation of blood oxygenation level dependent (BOLD) signal in anatomically separate brain regions while the participant rests passively in the scanner 6. Several reviews and meta-analyses have found altered RSFC in depression and anxiety, particularly in the DMN, CCN, and SN resting state networks7–10. Determining potential neural markers of the onset of internalizing disorders in high-risk youth is important for developing and implementing early intervention strategies to reduce illness severity or even prevent onset of the disorder.
Familial risk for depression and anxiety. Anxiety and depression both run in families, with genetic heredity of risk factors, as well as parenting and environmental effects interacting in high familial risk (subsequently “high-risk”) populations to increase risk for developing the disorder to 3–5 times that of low-risk populations11,12. High-risk adolescents show similar cognitive risk factors as depressed adults, with negative cognitive styles and biases in attention, interpretation, and memory of emotionally-valenced experiences11. Depression and anxiety both have similar hallmark characteristics such as increased rumination and negative self-thought, cognitive biases, and cognitive processing problems, as well as emotional control deficits8,10. These cognitive features have been linked to alterations in within-network functional connectivity of three intrinsic connectivity networks, the default mode network (DMN), the cognitive control network (CCN), and the salience network (SN)7–10.
Intrinsic resting-state brain networks and internalizing psychopathology. The DMN is comprised of the posterior cingulate cortex (PCC)/precuneus, middle and lateral parietal and temporal cortices, and medial prefrontal cortex (PFC)13. The DMN is de-activated during tasks requiring external attention, relative to passive rest, and is involved in self-referential processing, internal thought, and mental simulation, core processes that are altered in depression and anxiety13. In a study of individuals at high-familial risk for major depressive disorder (MDD) it was found that high- versus low-risk participants had increased DMN RSFC14. Increased RSFC of the DMN in patients with MDD has been shown to reflect increased negative self-thought and maladaptive rumination15,16. However, some studies have found decreased functional connectivity in individuals with high-trait anxiety, subthreshold depression, and MDD, indicating that while DMN RSFC is related to depression and anxiety the direction of effects are inconsistent17–19.
The cognitive control network (CCN) is a series of brain regions that are functionally coupled during performance of working memory, inhibitory control, selective attention, cognitive flexibility, and fluid reasoning20. It includes the anterior cingulate cortex (ACC)/pre-supplementary motor area, inferior frontal junction, anterior insular (AI) cortex, dorsolateral prefrontal cortex (DLPFC), dorsal pre-motor cortex, and posterior parietal cortex21. Altered functional connectivity of cognitive control regions such as the DLPFC and regions in the posterior parietal cortex are associated with cognitive control impairments and cognitive biases in depression22,23. The direction of reported RSFC abnormalities in the CCN in depression and anxiety is variable24. Some studies in high-risk populations as well as those with subthreshold depression or elevated trait anxiety have found reduced CCN RSFC17,22,25−27. Others found increased CCN connectivity in those with versus without anxiety disorders28. Still more have found both increased and decreased RSFC within the CCN when looking at connectivity between discrete regions24,29. Overall, while alterations of CCN RSFC are seen consistently across depression and anxiety, the direction is highly variable.
The salience network (SN) includes the amygdala, dorsal striatum, dorsal and subgenual ACC, and the AI and is involved in detection and processing of salient stimuli both internally and externally as well as recruiting necessary functional networks in response to said stimuli30. One of the primary roles of the SN is to control switching from the DMN to the CCN based on salience of external vs internal stimuli and thus may play a role in inter-network dysfunction in depression and anxiety where there can be a bias towards internal stimuli or excessive attention to perceived threatening stimuli16,28−30. In adolescent females increased within-SN RSFC was associated with greater subclinical anxiety and depressive symptoms31. Individuals with depressive and anxiety disorders, relative to those without, show impairments in the salience processing of emotional and threatening stimuli, often overattributing salience to neutral stimuli30. The SN is one of the least studied RSFC networks in depression and anxiety and as such the direction of alterations in RSFC in depression and anxiety is still to be elucidated.
While FC of these networks has been linked to subclinical depressive and anxiety symptoms and may differentiate those with versus without clinically significant depression or anxiety. However, the direction of association is inconsistent, and it is unknown if alterations in these networks are a result of the disorders or exist prior to the onset of the disorder and confer vulnerability to their development4,5. As such these networks’ RSFC may act as premorbid markers of the onset of depression and anxiety in at-risk youth. Testing this possibility requires a sample of adolescents at high risk for these disorders but who have yet to develop them prior to neuroimaging.
Overview and objectives. There is limited longitudinal research in adolescents at high familial risk for depression and anxiety predicting episode onset as a function of functional connectivity in the DMN, CCN, and SN resting state networks5. This study therefore examined whole brain RSFC of the CCN, DMN, and SN as possible neural markers of risk for first lifetime onsets of internalizing disorders in adolescents at high familial risk. This will aid in determining if the altered RSFC seen in depressed or anxious adults represents a premorbid vulnerability factor for depression and anxiety in high-risk teens. We hypothesize that altered functional connectivity between the CCN, DMN, SN, and the rest of the brain will longitudinally predict first lifetime onset of a diagnosable episode of an internalizing disorder. It is important to understand alterations in RSFC in different stages of illness, particularly in pre-morbid at-risk youth, as associations of these alterations with internalizing disorders may vary depending on disorder stage.