Læknablaðið - 01.09.2014, Page 19

LÆKNAblaðið 2014/100 451
ENGLISH SUMMARY
over the past 30 years evidence has been growing that cannabis use
increases the risk for psychosis which could develop into schizophrenia
in a proportion of cases. over the past decade many studies have been
published which clarify the association between cannabis use and psyc-
hosis. The aim of this review is to examine this association. A systematic
search yielded 14 cohort studies carried out in 9 cohorts and 9 case-
control studies. When the results of these studies are taken together
they unambiguously support that cannabis use is an independent risk
factor for psychosis and may also give rise to chronic psychotic disor-
ders like schizophrenia. A dose dependent link is present because more
frequent use associates with greater risk. The studies also show that
cannabis-use in adolescence is associated with greater risk of deve-
loping psychosis than commencing the use of cannabis in adulthood.
Further studies are needed to explain this association since psychotic
disorders take years to evolve and it remains difficult to measure both
the explanatory and the response variable and their complex relations-
hip. The results emphasize the need to enhance public knowledge on the
possible consequences of cannabis use and the fact that it cannot be
predicted who will experience transient psychosis and who will develop
a chronic psychotic disorder.
Does the use of cannabis increase the risk for psychosis and the development of schizophrenia?
Arnar Jan Jonsson1, Hera Birgisdottir1, Engilbert Sigurdsson1,2
key words: Cannabis, psychosis, schizophrenia, association.
Correspondence: Engilbert Sigurdsson, engilbs@landspitali.is
1Faculty of Medicine, University of Iceland, 2Mental Health Services, Landspitali–University Hospital.
Y F I R L I T