Study Participants and Protocol

Twenty individuals with long-term TBI-MF (minimum 5 months after injury) were recruited from the Department of Neurology, Sahlgrenska University Hospital, Gothenburg. Inclusion criteria were as follows: diagnosed with mild TBI according to the definition proposed by The World Health Organization Collaborating Centre for Neurotrauma Task Force (Carroll et al., 2004); scoring above the cut-off score of 10.5 on the Mental Fatigue Scale (MFS) (Johansson and Rönnbäck, 2014); aged 20–65 years and not suffering from any other psychiatric or neurological disorders. All participants had recovered well, were independent in their daily living, with the exception of their prolonged MF. Twenty-one healthy controls who neither suffered from MF (below 10.5 points on MFS), nor did they have any psychiatric or neurological disorders, were recruited at the request of the general community. The study was approved by the regional Ethical Review Board in Gothenburg (reference number: 028-16). The participants gave their informed written consent before the assessment and were told that they could withdraw at any time.