Abstract
Background:
The degree to which cannabis use causes long term harm to mental functioning
is contentious.
Objective:
To determine the evidence for residual and long term effects of cannabis use on mental
functions.
Method:
Comprehensively review human studies addressing detrimental effects on human mental
and life functioning.
Results:
Heavy use causes immediate effects on perception, mood and sedation, but also deficits in
cognitive ability. But cessation following heavy use has withdrawal effects and is associated with
residual effects on cognition that may last for several weeks. Heavy use also raises the risk of impoverishment
of life outcomes and a decline in socioeconomic status as well as the risk of mental
health problems. Young age at the start of heavy cannabis use causes a risk of lifelong detrimental
effects, and as a worst case together with genetic vulnerability exacerbate a predisposition to
schizophrenia.
Conclusion:
Heavy regular use of cannabis that begins in adolescence heightens the risk of longterm
impairment of life and mental functioning.