title: Neurobiological alterations induced by exercise and their impact on depressive disorders [corrected].
abstract: BACKGROUND
  The impact of physical activity on brain metabolic functions has been investigated in different studies and there is growing evidence that exercise can be used as a preventive and rehabilitative intervention in the treatment of depressive disorders. However, the exact neuronal mechanisms underlying the latter phenomenon have not been clearly elucidated. The present article summarises key results derived from studies that focussed on the neurobiological impact of exercise on brain metabolic functions associated with depressive disorders. Since major depressive disorder (MDD) is a life threatening disease it is of great significance to find reliable strategies to prevent or to cure this illness. Therefore, the aim of this paper is to review (1) the physiological relationship between physical activity and depressive disorders and (2) the potential neurobiological alterations induced by exercise that might lead to the relief of mental disorders like depression.
  
  
  METHODS
  We searched electronic databases for literature concerning the relationship between exercise and depression from 1963 until 2009.
  
  
  RESULTS
  The data suggests an association between physical inactivity and higher levels of depressive symptoms. Properly designed studies could show that exercise training can be as effective as antidepressive medications.
  
  
  CONCLUSIONS
  The exact mechanisms how exercise affects the brain are not fully understood and the literature lacks of well designed studies concerning the effects of exercise training on depressive disorders. But the observed antidepressant actions of exercise are strong enough that it already can be used as an alternative to current medications in the treatment of depressive disorders.
authors.affiliation: Department of Neurology, Psychosomatic Medicine, and Psychiatry, Institute of Health Promotion and Clinical Movement Science, German Sports University Cologne, Germany.
authors.forename: Ingo
authors.initials: I
authors.lastname: Helmich
authors.forename: Alexandra
authors.initials: A
authors.lastname: Latini
authors.forename: Andre
authors.initials: A
authors.lastname: Sigwalt
authors.forename: Mauro Giovanni
authors.initials: MG
authors.lastname: Carta
authors.forename: Sergio
authors.initials: S
authors.lastname: Machado
authors.forename: Bruna
authors.initials: B
authors.lastname: Velasques
authors.forename: Pedro
authors.initials: P
authors.lastname: Ribeiro
authors.forename: Henning
authors.initials: H
authors.lastname: Budde