“There are a great many young people, including some of the brightest and best who have been using marijuana now more or less regularly for three or four years.   Addiction or even habituation is denied.  The smoking is said to be simply for pleasure.

Untoward effects are usually, although not always, denied.  But the experienced clinician observes in many of these individuals personality changes that seem to grow subtly over long periods of time

• diminished drive
• lessened ambition
• decreased motivation
• apathy
• shortened attention span
• distractibility
• poor judgment
• impaired communication skills
• loss of effectiveness
• introversion
• magical thinking
• derealisation
• depersonalisation
• diminished capacity to carry out complex plans or prepare realistically for the future
• a peculiar fragmentation on the flow of thought
• habit deterioration
• progressive loss of insight.”