This short youtube clip is a must see for all those that have been convinced that cannabis causes mental health issues.
The argument has been used as propaganda tool for way too long, time for expert advice.

Derived for the documentary "A Culture High".
These two renowned professors, Dr. Lester Grinspoon and Dr David John Nutt, give their well educated opinions;

Dr. Lester Grinspoon (born June 24, 1928) is Associate Professor Emeritus of Psychiatry at Harvard Medical School. Grinspoon was senior psychiatrist at the Massachusetts Mental Health Center in Boston for 40 years. Dr. Grinspoon is a fellow of the American Association for the Advancement of Science and the American Psychiatric Association. He was founding editor of the The American Psychiatric Association Annual Review and the Harvard Mental Health Letter. Grinspoon was editor of the Harvard Mental Health Letter for fifteen years.

David John Nutt (born 16 April 1951) DM FRCP FRCPsych FMedSci is a British psychiatrist and neuropsychopharmacologist specialising in the research of drugs that affect the brain and conditions such as addiction, anxiety and sleep. He was until 2009 a professor at the University of Bristol heading their Psychopharmacology Unit. Since then he has been the Edmond J Safra chair in Neuropsychopharmacology at Imperial College, London. Nutt was a member of the Committee on Safety of Medicines, and was President of the European College of Neuropsychopharmacology. His book "Drugs without the hot air" (UIT press) won the Transmission Prize for Communicating Science in 2014