A study of more than 250,000 service members begun in 2001 released some preliminary findings on Friday, to celebrate the effort's 20th anniversary. Among them is that a plurality of male troops and veterans report tinnitus, or ringing of the ears, as their No. 1 health complaint. For women, the biggest issue is depression, though among women in the reserve component, migraines slightly edge out depression. The Millennium Cohort Study, inspired by concerns about the health effects of serving in Vietnam and the Gulf War, began in 2001 and has enrolled new waves of subjects every few years. "The goal of the study is to understand the impact of military service, including deployments and other occupational exposures, on the long-term physical health, mental health, and quality of life of service members," according to a report released Friday, which presents data from 2001 to 2016. One of the principal findings is top health concerns among troops. Among men, 24 percent repor