The Role of White Matter Connections in Adolescent Mental Health and Cognition

What's the science?

The brain’s white matter pathways connect many different regions of the brain, and these connections undergo immense change during adolescence. Psychiatric disorders or their symptoms (e.g. anxiety, depression, obsessive-compulsive disorder, attention deficit hyperactivity disorder, post-traumatic stress disorder) often develop during this time. This week in JAMA Psychiatry, Alnaes and colleagues report that cognition and psychopathology symptoms are related to the brain’s connections in the frontal lobe.

How did they do it?

6487 adolescents (without a diagnosed mental disorder) completed 1) reports on a wide variety of clinical /psychopathological symptoms, and 2) cognitive tests. Of these adolescents, 748 had MRI scans of the brain’s white matter connections, and 2946 had genetic testing done. They assessed whether psychopathological symptoms and cognitive scores were heritable (ie. genetically inherited) and whether these scores were related to brain connectivity patterns. They then used a robust technique called machine learning to test relationships, meaning they ensured that the proposed model of the relationship between the brain and cognition/psychopathy was accurate in multiple different subgroups of participants.

What did they find?

Weaker connections in two of the brain’s white matter tracts (uncinate fasciculus and inferior fronto-occipital fasciculus) were associated with lower cognitive scores, and a greater number of psychopathological symptoms. Anxiety, antisocial behaviour, and psychosis were correlated with these connections. Genetic variance explained 18% of an individual’s cognitive score and 16% of their general psychopathy score.

William Hirstein. Diagram by Katie Reinecke.,  White matter fiber tracts , colour by BrainPost,  CC BY 3.0

William Hirstein. Diagram by Katie Reinecke., White matter fiber tracts, colour by BrainPost, CC BY 3.0

What's the impact?

This study found that psychopathological symptoms in adolescents and lower cognitive scores were predicted by lower connectivity in pathways of the brain’s frontal lobe. These pathways connect the frontal lobe with other regions known to be involved in emotion and cognition. Lower connectivity in frontal white matter pathways could play a role in the development of psychiatric disorders in youth.

D. Alnaes et al., Association of Heritable Cognitive Ability and Psychopathology With White Matter Properties in Children and Adolescents. JAMA Psychiatry. (2018) Access the original scientific publication here.