Cognitive behavioural therapy for MS-related fatigue explained: A longitudinal mediation analysis. - van den Akker, L.E.; Beckerman, H.; Collette, E.H.; Knoop, H.; Bleijenberg, G.; Twisk, J.W.; Dekker, J.; de Groot, V.; TREFAMS-ACE study group (Journal of Psychosomatic Research, 2018)