This is not so of marijuana. Recent scientific studies show that marijuana in no way adversely effects the lungs, mind or body.
Not so fast there, recent health studies are showing mental health problems with some users.
Marijuana and Mental Health
A number of studies have shown an association between chronic marijuana use and increased rates of anxiety, depression, and schizophrenia. Some of these studies have shown age at first use to be an important risk factor, where early use is a marker of increased vulnerability to later problems. However, at this time, it is not clear whether marijuana use causes mental problems, exacerbates them, or reflects an attempt to self-medicate symptoms already in existence.
Chronic marijuana use, especially in a very young person, may also be a marker of risk for mental illnesses - including addiction - stemming from genetic or environmental vulnerabilities, such as early exposure to stress or violence. Currently, the strongest evidence links marijuana use and schizophrenia and/or related disorders. 4 High doses of marijuana can produce an acute psychotic reaction; in addition, use of the drug may trigger the onset or relapse of schizophrenia in vulnerable individuals.