Pain medications should be used only as directed and as little as possible. This could probably prevent many of the daily headaches that occur in those who suffer migraines. Reduction of stress and avoidance of any food triggers can also help in some cases. Relaxation methods and treatment of any depression may also help prevent some cases.
The main long-term effects are related to the severity of headaches. Those with severe headaches may be unable to engage in regular activities. The headaches themselves pose no threat to physical health in most cases. Severe migraines are quite rare but may cause stroke or paralysis.
Mixed tension migraines are not contagious and pose no risk to others.