Yes, the deduction covers post-tax health insurance payments for you, your spouse, or your dependents.
Missouri does not make this obvious in their form instructions. But nothing is more official than the source of the law:
7. (1) As used in this subsection, "qualified health insurance premium" means the amount paid during the tax year by such taxpayer for any insurance policy primarily providing health care coverage for the taxpayer, the taxpayer's spouse, or the taxpayer's dependents.
http://www.moga.mo.gov/mostatutes/stathtml/14300001211.html