There has been a shift from the psychological studies of the effects of severe TBI that focused on cognitive functions to concentrate on extensive behavioral consequences. Such behavioral consequences were found to have more significant distress in comparison to physical disabilities due to TBI. It also led to substantial life consequences such as relationship problems, social isolation, and unemployment. Individuals who have witnessed significant changes in a person’s behavioral response describe them as impulsive, severely irritable, apathetic, and lacking awareness. These behavioral changes are linked to impaired functioning of specific front-subcortical circuits. Externalizing psychopathology is also present after TBI, including substance misuse and substance use disorders.