1. There is no establishment of causality, but the article pretends there is. People who use marijuana may use it because they have high-stress lives.
2. It only applies to smokers. About 70% of the marijuana products at the dispensaries I've been to are not meant to be smoked. To quote the original article ['Recreational marijuana is primarily smoked; we hypothesize that like cigarette smoking, marijuana use will be associated with increased cardiovascular mortalities']
3. No link to original study. [I think it's this: http://journals.sagepub.com/doi/pdf/10.1177/2047487317723212]
4. This could be a million different things. This could be related to the stress of being afraid of being fired, or arrested. This could be tainted drugs from bad suppliers. This could be because marijuana smokers are more likely to take drugs that do change blood pressure.