Will there be a pre-existing condition waiting period when adding a new spouse to my health insurance?

I'm getting married next month and adding my fiance to my employer-based health insurance plan. He has a pre-existing condition and no insurance. The insurance company said they aren't allowed to deny coverage, so that's good. But are they still allowed to impose a waiting period before he can get medications or treatment for *that specific condition*? I see a lot of things saying they can't do this to kids but nothing about adults.
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They can impose a waiting period since he doesn't currently have insurance. The waiting period will depend upon the insurance company, the policy, and your state regulations but can be up to 12 months.
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