Cancer: No evidence linking smoking cannabis to increased cancer risk associated with tobacco use.

Heart Attack: Some evidence suggesting cannabis smoking may trigger a heart attack. More research needed to determine risk of heart attack, stroke and diabetes.

Respiratory Disease: Regular smoking of cannabis associated with more frequent chronic bronchitis episodes, chronic cough and phlegm production. Unclear if cannabis use linked to chronic obstructive pulmonary disease or asthma.

Mental Health: Likely to increase risk of developing schizophrenia, other psychoses and social anxiety disorders. Also increases risk of developing depression. Heavy users more likely to report suicidal thoughts than non-users.

Psycosocial: Learning, memory and attention impaired after immediate cannabis use but limited evidence suggesting such impairments continue after the cessation of smoking cannabis.

 .
Listen what this Emeritus Associate Professor of Psychiatry at Harvard Medical School says about the correlation between cannabis and schizophrenia.

references;
http://www.news.com.au/national/breaking-news/cannabis-still-harmful-to-health-report/news-story/3b8bc97299c233693027417e4c608f6e