Healthy volunteers
Not accepted
Inclusion Criteria:
* The inclusion criteria was continuous enrollment for at least 12 months in the Integrated Health Care Information Services (IHCIS) National Managed Care Benchmarked Database during the interval between January 1, 1997 and March 31, 2008, age 18 years of age and older, and continuous eligibility for pharmacy benefits during IHCIS enrollment.
Exclusion Criteria:
* Exclusion criteria were membership in the Integrated Health Care Information Services (IHCIS) National Managed Care Benchmarked Database without a valid gender or age record, less than 12 months continuous enrolment, and member residence in the 'national' census region. This latter grouping represented members who were either not living in the continental US or were masked for confidentiality reasons based on IHCIS archiving of data per the Health Insurance Portability and Accountability Act.