title: Exercise reduces depressive symptoms in adults with arthritis: Evidential value.
abstract: OBJECTIVE
  To determine whether evidential value exists that exercise reduces depression in adults with arthritis and other rheumatic conditions.
  
  
  METHODS
  Utilizing data derived from a prior meta-analysis of 29 randomized controlled trials comprising 2449 participants (1470 exercise, 979 control) with fibromyalgia, osteoarthritis, rheumatoid arthritis or systemic lupus erythematosus, a new method,P-curve, was utilized to assess for evidentiary worth as well as dismiss the possibility of discriminating reporting of statistically significant results regarding exercise and depression in adults with arthritis and other rheumatic conditions. Using the method of Stouffer,Z-scores were calculated to examine selective-reporting bias. An alpha (P) value < 0.05 was deemed statistically significant. In addition, average power of the tests included inP-curve, adjusted for publication bias, was calculated.
  
  
  RESULTS
  Fifteen of 29 studies (51.7%) with exercise and depression results were statistically significant (P< 0.05) while none of the results were statistically significant with respect to exercise increasing depression in adults with arthritis and other rheumatic conditions. Right-skew to dismiss selective reporting was identified (Z= -5.28,P< 0.0001). In addition, the included studies did not lack evidential value (Z= 2.39,P= 0.99), nor did they lack evidential value and wereP-hacked (Z= 5.28,P> 0.99). The relative frequencies ofP-values were 66.7% at 0.01, 6.7% each at 0.02 and 0.03, 13.3% at 0.04 and 6.7% at 0.05. The average power of the tests included inP-curve, corrected for publication bias, was 69%. Diagnostic plot results revealed that the observed power estimate was a better fit than the alternatives.
  
  
  CONCLUSIONS
  Evidential value results provide additional support that exercise reduces depression in adults with arthritis and other rheumatic conditions.
authors.affiliation: Department of Biostatistics, School of Public Health, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506-9190, United States.
authors.forename: George A
authors.initials: GA
authors.lastname: Kelley
authors.affiliation: Department of Biostatistics, School of Public Health, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506-9190, United States.
authors.forename: Kristi S
authors.initials: KS
authors.lastname: Kelley
keywords: Adults; Arthritis; Bias; Exercise; Meta-analysis; Physical activity; Physical fitness; Publication bias; Rheumatic disease; Systematic review