I know that an unpaid medical bill affects the credit score if it is sent to collections. But is there any more adverse affect that it creates?
The effect of an unpaid medical bill largely relies on how it is reported to the credit agencies. In the USA if the bill is put in collections without a late report, paying the bill will remove the black mark entirely. If it is reported late first, it will remain on your report for 7 years. Failure to pay an outstanding bill after its put in collections can lead to legal action (as pointed out by @ceejayoz), which can create its own set of problems.
Black marks on your credit and/or legal actions related to unpaid debts can impact every facet of modern life unfortunately. These items will show up on background checks as well as credit checks. Job applications, car loans, mortgages, applications for renting or leasing, even purchasing firearms can all be affected by an imperfect financial record. Not every check listed will always include a credit report, and not every check will result in questions even if the check comes back with a credit report.