Smoking and Pulmonary function

Cannabis should not  necessarily be viewed as a harmless  substance.  Its active constituents may "produce a variety of physiological and euphoric effects. As a result, there may be some populations that  are susceptible to increased risks from the use of  cannabis, such as adolescents, pregnant  or nursing mothers, and patients who have a family history of mental  illness. Patients with hepatitis C, decreased lung function (such as chronic obstructive pulmonary disease),  or who have a history of heart  disease or  stroke may  also be at  a greater  risk  of  experiencing adverse side effects  from
cannabis. As  with any  medication,  patients  should consult  thoroughly  with  their  physician  before deciding whether the medical use of cannabis is safe and appropriate.

The  persisting  Schedule  I  classification  of  cannabis  that  the  government  maintains  is  itself  a smokescreen  that  is  directly  discordant  with  authoritative,  independent,  medico-scientific evidence-based assessments. Publishing in the open-access scientific literature housed in the U.S.  National  Institutes of  Health's 
National  Library  of  Medicine,  clinical  investigators  who  oversaw  seven  separate,
government-authorised, gold-standard design clinical  trials of the safety and efficacy of  smoked and vaporised  inhaled  cannabis  for  specific  indications  conducted  at  University  of  California  medical centers over a 10 years period. 

From 2002–2012 the study involved over 300 human subjects reported in an article entitled “Medical Marijuana:  Clearing  Away  the  Smoke”  that  all  trials  independently  showed  benefit.  The  authors concluded  that  the  Schedule  I  classification  of  cannabis,  based  on  the  evidence  collected  and reviewed, is “not tenable,” “not accurate,” and one of the main “obstacles to medical progress.”