title: Examining the relationship between clinical monitoring and suicide risk among patients with depression: matched case-control study and instrumental variable approaches.
abstract: OBJECTIVE
  To assess the relationship between closer monitoring of depressed patients during high-risk treatment periods and death from suicide, using two analytic approaches.
  
  
  METHODS
  VA patients receiving depression treatment between 1999 and 2004.
  
  
  METHODS
  First, a case-control design was used, adjusting for age, gender, and high-risk days (1,032 cases and 2,058 controls). Second, an instrumental variable (IV) approach (N=714,106) was used, with IVs of (1) average monitoring rates in the VA facility of most use and (2) monitoring rates of VA facilities weighted inversely by distance from patients' residences.
  
  
  RESULTS
  The case-control approach indicated a modest increase in suicide risk with each additional visit (odds ratio=1.02; 95 percent confidence interval=1.002, 1.04). The "facility used" IV estimate indicated near zero change in risk (0.0008 percent increase; p=.97) with each additional visit, while the distance-weighted IV estimate indicated a 0.032 percent decrease in risk (p=.29). An alternative analysis assuming a threshold effect of ≥4 visits during high-risk periods also showed a decrease (0.15 percent; p=.08) using the distance IV.
  
  
  CONCLUSIONS
  The IV approach appeared to address the selection bias more appropriately than the case-control analysis. Neither analysis clearly indicated that closer monitoring during high-risk periods was significantly associated with reduced suicide risks, but the distance-weighted IV estimate suggested a potentially protective effect.
authors.affiliation: Department of Veterans Affairs Health Services Research and Development, Ann Arbor Center of Excellence (COE), Ann Arbor, MI 48109, USA.
authors.forename: Hyungjin Myra
authors.initials: HM
authors.lastname: Kim
authors.forename: Daniel
authors.initials: D
authors.lastname: Eisenberg
authors.forename: Dara
authors.initials: D
authors.lastname: Ganoczy
authors.forename: Katherine
authors.initials: K
authors.lastname: Hoggatt
authors.forename: Karen L
authors.initials: KL
authors.lastname: Austin
authors.forename: Karen
authors.initials: K
authors.lastname: Downing
authors.forename: John F
authors.initials: JF
authors.lastname: McCarthy
authors.forename: Mark
authors.initials: M
authors.lastname: Ilgen
authors.forename: Marcia
authors.initials: M
authors.lastname: Valenstein
mesh_terms: D000328:Adult; D000359:Aftercare / Q000458:organization & administration*; D000368:Aged; D000553:Ambulatory Care / Q000458:organization & administration*; D016022:Case-Control Studies; D002423:Cause of Death; D015986:Confounding Factors, Epidemiologic; D003627:Data Interpretation, Statistical; D003866:Depressive Disorder / Q000188:drug therapy* / Q000401:mortality; D016903:Drug Monitoring / Q000706:statistics & numerical data*; D015987:Effect Modifier, Epidemiologic; D005260:Female; D006302:Health Services Research; D006787:Hospitals, Veterans; D006801:Humans; D016014:Linear Models; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012307:Risk Factors; D015983:Selection Bias; D013405:Suicide / Q000706:statistics & numerical data*; D014481:United States / Q000453:epidemiology; D000092864:Suicide Prevention