1 October 2019 | Volume 10 | Article 785 BRIEF RESEARCH REPORT doi: 10.3389/fpsyt.2019.00785 published: 25 October 2019 Frontiers in Psychiatry | www.frontiersin.org The Association Between Cardiorespiratory Fitness and Cognition Appears Neither Related to Current Physical Activity Nor Mediated by Brain-Derived Neurotrophic Factor in a Sample of Outpatients With Schizophrenia Tom Langerud Holmen 1 *, Jens Egeland 1,2 , Eivind Andersen 3 , Jon Mordal 1 , Ole Andreas Andreassen 4,5 , Thor Ueland 5,6,7 , Therese Torgersen Bigseth 1 , Gry Bang-Kittilsen 1 and John Abel Engh 1 1 Division of Mental Health and Addiction, Vestfold Hospital Trust, Tønsberg, Norway, 2 Department of Psychology, University of Oslo, Oslo, Norway, 3 Faculty of Humanities, Sports and Educational Science, University College of Southeast Norway, Notodden, Norway, 4 NORMENT Centre, Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway, 5 Institute of Clinical Medicine, University of Oslo, Oslo, Norway, 6 Research Institute of Internal Medicine, Oslo University Hospital, Rikshospitalet, Oslo, Norway, 7 KG Jebsen Thrombosis Research and Expertise Centre, University of Tromsø, Tromsø, Norway Objective: We investigated whether levels of current physical activity (PA) contribute to the established relationship between cardiorespiratory ftness (CRF) and cognition in schizophrenia and whether brain-derived neurotrophic factor (BDNF) or its precursor proBDNF mediates this relationship. Method: Sixty-one outpatients with schizophrenia spectrum disorders participated. Neurocognition was assessed with the Wechsler Adult Intelligence Scale (WAIS) and nine subtests from the MATRICS battery comprising a neurocognitive composite score (NCS). CRF was assessed with peak oxygen uptake (VO 2peak ) measured directly during a maximum exercise test. Current PA levels were objectively assessed by an accelerometer worn for four consecutive days. BDNF and proBDNF were measured in fasting blood. Four serial parallel mediation analyses and two additional parallel mediation analyses were conducted, while controlling for age and sex at all levels. Results: No direct effects were found between PA measures and WAIS or NCS. No signifcant mediating effects of CRF or BDNF/proBDNF were detected. Conclusion: The results do not support the hypothesis that PA contributes to the naturally occurring relationship between CRF and cognition in schizophrenia or the hypothesis that BDNF or proBDNF mediates this relationship. The results arguably Edited by: Philip D. Harvey, University of Miami, United States Reviewed by: Martin Strassnig, University of Miami, United States David Kimhy, Icahn School of Medicine at Mount Sinai, United States *Correspondence: Tom Langerud Holmen lantom@siv.no Specialty section: This article was submitted to Schizophrenia, a section of the journal Frontiers in Psychiatry Received: 17 June 2019 Accepted: 02 October 2019 Published: 25 October 2019 Citation: Holmen TL, Egeland J, Andersen E, Mordal J, Andreassen OA, Ueland T, Bigseth TT, Bang-Kittilsen G and Engh JA (2019) The Association Between Cardiorespiratory Fitness and Cognition Appears Neither Related to Current Physical Activity Nor Mediated by Brain-Derived Neurotrophic Factor in a Sample of Outpatients With Schizophrenia. Front. Psychiatry 10:785. doi: 10.3389/fpsyt.2019.00785