My 20 year old son has his medical in 2 days time, he smokes weed but assures me he hasn't has any in around 3 weeks. Im worried this will show up and stop our application for PR going through. He has no intention of following us to Canada but for our application to go through we have to add him on our application as he's under 22 years. Do they check for drugs in the blood/urine tests?