There is no definitive evidence saying that smoking marijuana will directly lead to an asthma attack, however there has been research done on the effects marijuana can have on the lungs. Just like tobacco cigarettes, marijuana usually involves inhaling smoke. Marijuana smoke is very similar to tobacco smoke and contains many of the same particles, such as carcinogens, that can cause cancer. Smoke from tobacco or marijuana can irritate the lungs, and may cause acute inflammation. Marijuana smoke is usually inhaled deeper and held longer than tobacco smoke, leaving you more exposed to the carcinogens and other irritants in the smoke. Due to this, general irrigation of the lungs can occur after marijuana use. Symptoms can include, wheeziness, shortness of breath, and phlegm production.
So, if you have asthma and decide to smoke marijuana, your lungs may become irritated. Your symptoms may be more sever because of your chronic condition, and could possibly lead to an asthma attack. It is suggested that people with asthma avoid smoking marijuana and cigarettes.