Bridging mental health, cognition and the brain in mild traumatic brain injury: A multilayer network analysis of the TRACK-TBI study.

Insomnia was the only variable showing clinically significant impairment across affective and cognitive layer nodes in mTBI participants at 6-month follow-up.

• Cross-sectional data from 457 mTBI participants from the TRACK-TBI Longitudinal study at 6-month follow-up were analyzed.
• Four variables from self-report mental health questionnaires formed the affective layer, and eight cognitive test scores from the NIH toolbox formed the cognitive layer.
• Across all affective and cognitive layer nodes, only impairments in insomnia were noted in the sample.

Four nodes exceeded the a priori 80th percentile threshold on bridge strength scores, identifying them as key bridging nodes across affective, cognitive, and brain layers.

• The four key bridging nodes were insomnia severity, immediate verbal memory, somatisation, and processing speed.
• The bridge strength centrality metric was used to identify nodes that 'bridge' the affective, cognitive, and brain layers.
• An a priori 80th percentile threshold was applied to bridge strength scores to determine key nodes.

The multilayer network included structural brain measures from eight regions of the central executive and salience networks.

• Gray matter volumes from eight brain regions comprising the central executive and salience networks were extracted from anatomical MRI scans.
• These brain measures formed the brain layer of the multilayer network.
• The multilayer network approach examined relationships (edges) between all variables (nodes) across affective, cognitive, and brain layers.

This study constructed the first multilayer network in mTBI to examine cross-layer relationships between cognition, mental health, and structural brain measures.

• The multilayer network incorporated three distinct layers: an affective layer, a cognitive layer, and a brain layer.
• A total of 457 mTBI participants from the TRACK-TBI Longitudinal study provided chronic phase cross-sectional data at 6-month follow-up.
• Prior research had largely investigated symptoms in TBI in isolation using univariate approaches, ignoring interactions between symptoms and underlying large-scale brain networks.

The bridging nodes identified through multilayer network analysis are suggested as potential targets for developing more customized treatments for mTBI.

• Insomnia severity, immediate verbal memory, somatisation, and processing speed were identified as bridging nodes.
• The authors suggest these nodes may represent targets for future studies to develop 'more customized, efficient, and efficacious treatments to alleviate mental health symptoms and cognitive deficits in mTBI.'
• The multilayer network approach was proposed as a means to better capture interactions between symptoms that are missed by univariate methods.