Hi there ~
I understand your concerns. I am sorry to hear about he death of your son due to heroin
and marijuana abuse
. I believe that he was physiologically and psychologically dependent on those drugs to the point where it was lethal. What happens in dependence is a person starts to like the drug he uses and then starts abusing it to get the high. The high does not last and the person uses more and more of the substance to experience that high that was first experienced. This would make one psychologically dependent. In the meantime, the body also gets accustomed to the medication and when you go off of the medication one starts to have physical symptoms called withdrawals, which make the person go back on the substance again. The physiological and psychological dependence gets to point where one used the drugs too much and ultimately overdoses on the substances and that is usually the cause of death. I hope this helped explain your son's death and I am sorry for your loss.
I hope this helps. Take care and have a lovely day!