Pollen counts and suicide rates. Association not replicated

Woo JM, Gibbons RD, Rogers CA, Qin P, Kim JB, Roberts DW, Noh ES, Mann JJ, Postolache TT. Pollen counts and suicide rates. Association not replicated. Objective:  To replicate a previously reported association between pollen counts and county suicide rates in the continental United States, across space and time. Method:  The authors evaluated the relationship between airborne pollen counts and suicide rates in 42 counties of the continental United States, containing a pollen-counting station participating in the Aeroallergen Monitoring Network in the United States (N = 120 076 suicides), considering years’ quarter, age group, sex, race, rural/urban location, number of local psychiatrists, and median household income, from 1999 to 2002. The county-level effects were broken into between-county and within-county. Results:  No within-county effects were found. Between-county effects for grass and ragweed pollen on suicide rates lost statistical significance after adjustment for median income, number of psychiatrists, and urban vs. rural location. Conclusion:  Future research is necessary to reappraise the previously reported relationship between pollen levels and suicide rates that may have been driven by socioeconomic confounders.