CRP and major depressive disorder: A longitudinal study using Avon Longitudinal Study of Parents and Children (ALSPAC) data found that higher interleukin 6 levels at age 9 years were associated with subsequent higher risks of depression and psychotic episodes at ages 18 years6 and 24 years.7 A meta-analysis has shown that an increased C-reactive protein (CRP) level (>0.3 mg/dL; to convert to milligrams per liter, multiply by 10) is associated with increased rates of psychosis.8 However, these studies only examined inflammation at a single time point.