Has he been on the Adderall all this summer or did he take a break from it?
Could his depression have anything to do with school starting?
If you son is talking suicide, whether you think we might commit it or not, take him to the ER immediately. There, he could receive the counseling he needs and they could help stabilize his medication.
The problem these days with kids diagnosed with ADHD or any other psychological disorder is that they are only taking the medication without being seen at least weekly by a mental health therapist. This is where permanent change can take place.
Please do not take your son's suicidal talk lightly. This is a huge red flag that he needs counseling ASAP. Take him to the ER and please make sure that he is being seen by a therapist! Also, please don't allow his motivate or desire to talk to a therapist be the determining factor as to whether he should receive treatment. Most kids don't want to see a therapist. This is normal. Therapist are trained to counsel kids who don't want counseling.
At this point, Rob, you're in a crisis point. Right now, he literally doesn't feel good enough to kill himself. As you work through this, and he improves, he may get the energy to actually commit suicide. This is a pattern that's very common - you hear parents say he hit a low point and then was feeling better and then inexplicably he took his life. It isn't inexplicable - it actually takes a certain amount of energy and commitment to commit suicide. People don't usually kill themselves at their "lowest point".
Is there an alternative schooling situation that you can enroll him in where he won't have to be medicated? I don't sense taking him off stimulants entirely has been considered as a possible solution to his depression.
Best wishes.