Causes for coronary artery disease/coronary atherosclerosis in young adults?

i am in my late 20's and was diagnosed last week with CAD, coronary atherosclerosis which they said is classified as Chronic Ischemic Heart Disease & also unspecified essential hypertension (ICD 9 codes were 414.01 & 401.9).
everything i'm reading online to try and ease my mind about having this at such a young age is saying that usually when you have this at my age, it's caused by abuse of stimulant drugs like amphetamines and cocaine...i have never put a cigarette in my mouth, much less an illegial drug so i am wondering now what other causes could be.
i was diagnosed with mitral valve prolapse/regurg at age 12 so maybe that has something to do with it?
i also have adult ADHD and took Adderall 20 mg. 2x's a day for 2 years up until about 8 months ago when i decided to go the natural way and see how that would work...i know adderall is an amphetamine but i only took it 2 years off and on and never abused it.
sorry for the excess details, but hopefully someone out there can help!

How about stress ? I have a severe stress reaction in action movies, and my heart rate zooms up. Two years ago I actually suffered a valve strain watching a battle scene in the movie Troy.

Another common symptom that suggests drug use is arterial ectasia. That's the term for severely dilated arteries. I have that, so when in the ER for a minor heart attack, they saw that on my record and asked over and over if I used cocaine. Ectasia is 10 times more common in coke users.

With ectasia, blood flow slows, and its easier for bad cholesterol to collect and form blockages. The stretching leaves damage that the body tries to repair, but results in the initial blockages.

If you exercise very hard without warming up, that also puts a strain on the arteries, and might aggravate ectasia. I also did that, for decades.

Do everything the doctor recommends. E-mail me if you have questions on exercise for cardiac rehab. I've have been through it four times.