title: Habitual physical activity levels predict treatment outcomes in depressed adults: A prospective cohort study.
abstract: Exercise is an efficacious stand-alone therapy for mild-to-moderate depression, but little is known about the influence of physical activity levels on responses to depression treatment. This study aimed to prospectively assess the association between self-reported habitual physical activity levels and depression severity following a 12-week intervention.
  
  
  
  629 adults (75% women; aged 18-71years) with mild-to-moderate depression were recruited from primary care centres across Sweden and treated for 12weeks. The interventions included internet-based cognitive behavioural therapy (ICBT) and 'usual care' (CBT or supportive counselling). One third of all participants were taking anti-depressant medication. The primary outcome was the change in depression severity assessed using the Montgomery-Åsberg Depression Rating Scale (MADRS). Habitual physical activity levels were self-rated and based on the estimated frequency, duration and intensity of total physical activity, including planned exercise, 'during a typical week'. Prospective associations were explored using linear regression models (percentage change) with 95% confidence intervals (CI's).
  
  
  
  Following adjustment for relevant covariates, high levels of habitual physical activity were associated with larger relative reductions in depression severity compared to low physical activity (β=-9.19, 95% CI=-18.46, -0.09, p=0.052) and moderate physical activity (β=-10.81, 95% CI=-21.09, -0.53, p<0.05), respectively.
  
  
  
  Adults who routinely engage in high levels of physical activity respond more favourably to CBT-focused depression treatments than adults who engage in low-to-moderate levels of activity. The optimal level of physical activity associated with reductions in depression severity corresponds to consensus recommendations for maximizing general health. One limitation is the use of self-reported physical activity data.
authors.affiliation: Division of Epidemiology and Public Health Intervention Research (EPHIR), Department of Public Health Sciences, Karolinska Institutet, Solna 171 77, Sweden. Electronic address: Mats.hallgren@ki.se.
authors.forename: Mats
authors.initials: M
authors.lastname: Hallgren
authors.affiliation: Division of Epidemiology and Public Health Intervention Research (EPHIR), Department of Public Health Sciences, Karolinska Institutet, Solna 171 77, Sweden.
authors.forename: Olivia Aya
authors.initials: OA
authors.lastname: Nakitanda
authors.affiliation: The Swedish School of Sport and Health Sciences, Box 5626, Stockholm 114 86, Sweden.
authors.forename: Örjan
authors.initials: Ö
authors.lastname: Ekblom
authors.affiliation: Department of Physical Education and Sport Sciences, University of Limerick, Ireland; Health Research Institute (HRI), University of Limerick, Ireland.
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Herring
authors.affiliation: Behavioural Epidemiology Laboratory, Baker IDI Heart and Diabetes Institute, Melbourne, Australia.
authors.forename: Neville
authors.initials: N
authors.lastname: Owen
authors.affiliation: Physical Activity Laboratory, Baker IDI Heart and Diabetes Institute, Melbourne, Australia; Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Dunstan
authors.affiliation: Division of Epidemiology and Public Health Intervention Research (EPHIR), Department of Public Health Sciences, Karolinska Institutet, Solna 171 77, Sweden.
authors.forename: Björg
authors.initials: B
authors.lastname: Helgadottir
authors.affiliation: Division of Epidemiology and Public Health Intervention Research (EPHIR), Department of Public Health Sciences, Karolinska Institutet, Solna 171 77, Sweden.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Forsell
mesh_terms: D000328:Adult; D015928:Cognitive Behavioral Therapy / Q000379:methods; D003866:Depressive Disorder / Q000628:therapy*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D020407:Internet; D008297:Male; D011446:Prospective Studies; D012720:Severity of Illness Index; D013548:Sweden; D016896:Treatment Outcome
keywords: Depression; Exercise; Physical activity; Response; Treatment