What I know about cannabis, the patients who are receiving treatment to fight certain disorders must take into account the possible interactions between cannabis and the medicines they take. 

The effect of prescription drugs may increase or decrease when they are mixed with marijuana. In some cases, these interactions translate into an impediment to perform daily tasks; in others, they could lead to more serious disorders.

Some time ago I read an article that said the great majority of patients tolerate the combined effects of medicinal cannabis and prescription drugs. In some cases, marijuana may cause mild side effects, while in others, these effects should be taken more seriously. Cannabis by itself has never caused death as you say in your article, and there have been very few cases of diseases resulting from its abuse. Despite this, mixing different drugs or substances can have an unpredictable effect on every patient.