Possibly, the answer depends on the amount of support you provide and your plan.
You can deduct the premiums if the nondependent child is:
See the following from IRS Publication 502:
your child whom you don't claim as a dependent because of the rules for children of divorced or separated parents,
Any person you could have claimed as a dependent on your return except that person received $4,050 or more of gross income or filed a joint return, or
Any person you could have claimed as a dependent except that you, or your spouse if filing jointly, can be claimed as a dependent on someone else's 2016 return.
If you had family coverage when you added this individual to your policy and your premiums didn't increase, you can enter on Schedule A (Form 1040) the full amount of your medical and dental insurance premiums.
You can claim the premiums if you either provided more than half of this child’s support, or if you had family coverage when you added this child and her insurance coverage is not costing you increased premiums.