As I understand, in many states' insurance policies there may be a specific exclusion for autism spectrum disorders; specific exclusion means that the diagnosis and/or treatment is singled out for exclusion in the plan contract. It doesn't matter if the care is medically necessary or not, because the plan contract singles out autism spectrum disorders for exclusion; the question of medical necessity therefore becomes a moot point. Here is an article on the matter with a list of states that mandate insurance carriers in those states to cover the diagnosis and treatment of autism spectrum disorders:
http://www.pewstates.org/projects/state ... 5899496217
Basically, as it currently stands under the ACA, insurance companies may not drop your coverage, refuse you to issue you a policy, or charge you more for a pre-existing condition, but the carriers may still exclude coverage for categories of medically necessary care in the plans they issue, may still have blanket bans on treatment (medically necessary or not) for certain conditions, provided the law does not specifically require the insurance carrier to cover the diagnosis and/or treatment. It's not just autism that has this problem, but GID/gender dysphoria, too, where in most states all the plans on the exchanges specifically exclude all care (medically necessary or not) for GID/gender dysphoria.
Now, as I understand, for autism spectrum disorders, oftentimes your therapist can get around this problem by billing a different diagnosis, such as depression or anxiety.
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"You have a responsibility to consider all sides of a problem and a responsibility to make a judgment and a responsibility to care for all involved." --Ian Danskin