PTH and major depressive disorder: While the time after baseline is important to assess suicide risk, not restricting the time period for the selected covariates will introduce biases, as PTH itself could affect the likelihood of developing MDD, PTSD, etc. Also, the delay in PTH diagnosis in veterans relative to headache onset suggests that the higher baseline rates seen in the PTH group may only represent the start of increasingly divergent rates of comorbidities between the groups.