Soumerai 2008

Methods	Controlled cohort study ‐ ITS with monthly data points
Participants	Maine, USA, Medicaid and Medicare, newly treated patients with schizophrenia diagnosis n=4600
Interventions	PA policy on atypical antipsychotics
Outcomes	Drug use, drug costs, time to treatment discontinuation
Notes	Intervention state: Maine, control state: New Hampshire; Medicaid claims for 201‐2004. Policy period too short (policy discontinued) and study lacked power to detect treatment discontinuities.
Risk of bias
Bias	Authors' judgement	Support for judgement
Incomplete outcome data (attrition bias) All outcomes	Low risk	Any undocumented difference in the proportion of missing data in the administrative datasets pre‐ and post‐intervention is unlikely to overturn study results "Only Maine had enough patients to analyse utilization trends by preferred and nonpreferred categories"
Selective reporting (reporting bias)	Low risk	All outcomes listed in the methods section are reported in the results section
Other bias	Low risk	Treatment discontinuities common in schizophrenia. Maine had a significantly greater percentag of patients in the 18‐34 categories ‐ could confound the treatment discontinuities however these were not a study outcome.
Knowledge of allocated interventions adequately prevented during the study	Low risk	Outcomes are objective measures of healthcare utilization
Intervention independent of other changes	High risk	"The termination of Maine's PA policy after out study began resulted in limited follow‐up, reducing our statistical power to detect treatment discontinuities among newly treated patients"
The shape of intervention pre‐specified?	Low risk	The point of analysis is the point of intervention; ie, the date the policy intervention was implemented was used to delineate pre and post policy time periods with adequate data points to capture the shape of the pattern of intervention effect over time.
Intervention unlikely to affect data collection?	Low risk	Objective data obtained from an administrative database with standard collection rules.