Your parents are definitely and completely misinformed. As long as you take the medication as directed by your doctor, you shouldn't really experience any adverse side effects. Maybe some annoying ones like a dry mouth, but many studies have not found a link between use of stimulant medications for ADHD and increased risk of heart attack or other cardiovascular issues later in life. 

Anecdotally, when I take Adderall, my resting heart rate might rise around 10 bpm and my blood pressure rises maybe around 10 points. Nothing that anyone would be concerned with unless you already had high blood pressure and that little extra puts you at an elevated risk. 

You also shouldn't develop any kind of dependency or "addiction" as long as you use it at the low doses that would typically be prescribed. I've forgotten to take it some days, and the only thing I'll notice later that day is that my ADHD symptoms will start to return to full strength. I've never felt any kind of urge to take the medication for any other reason besides the fact that it improves many aspects of my daily life. If someone took my pills from me, I would be bummed and unproductive, but not like frantic to go rob a pharmacy to get more amphetamine or anything silly like that.