My son has a high iq, but also high drug use. how do i help him break free?

Talk with him: Talk with your son about your concerns. It has nothing to do with his high iq. If he is living in your home, you have the right to make rules about his drug use. If he wants help ( it needs to be his choice if he is an older teen or adult), you can help him find a good therapist or treatment program. Remind him that you love him, no matter what, but you don't like his drug use.