Does Adderall have any serious side affects for a healthy, non-prescribed user?

Absolutely it has potentially serious side effects. That is why it is designated a controlled substance and should only be used in a medically monitored and screened patient, by prescription.

It is an amphetamine, a stimulant with known cardiovascular and nervous system side effects, as well as the potential for addiction and dependency. It raises blood pressure and heart rate, with the potential to cause heart rhythm disturbances, including potentially life threatening rhythms. Sudden deaths have been reported in individuals on Adderall, both used recreationally and prescribed. It can also potentially induce seizures in vulnerable individuals.

Self medicating is risky and unwise, especially if other recreational or prescription drugs are being used simultaneously.