Introduction:
Since the 1990s is it known that there is a relationship between the use of cannabis and schizophrenia spectrum disorders (Thornicroft, 1990). Several psychologists have investigated this relation and have come to different answers regarding its importance. In many countries around the world, the attitude towards the use of cannabis is getting more liberal in recent times. This liberalization of the illegal drug use leads apparently to an increasing trend of cannabis use, especially among adolescents and young adults. Therefore the topic of a relationship between the use of marijuana and hence the onset of schizophrenic disorder has gained new relevance in the science of Psychology. New research about the relationship of cannabis and schizophrenia has been conducted in order to gain more knowledge not only about the connection but also about what actually triggers or at least contributes to the onset of schizophrenia.
This paper will deal with the question whether there really is a relationship between the use and abuse of cannabis and the development and onset of schizophrenia and if so, what the relation exactly is. There are five different hypotheses about the relation of cannabis and schizophreniform disorder. The self-medication hypothesis, use of cannabis as result of coping with negative symptoms of schizophrenia; the other drug hypothesis, other drugs taken together with cannabis as cause for later schizophrenia; the confounding hypothesis, relation between cannabis and schizophrenia is caused by a third unknown variable; the interaction hypothesis, cannabis as a trigger cause for schizophrenic disorder only in people who are vulnerable (genetically or another way) to schizophrenia; and the etiological hypothesis, use of cannabis as a unique contributing factor to the onset of schizophrenia (Smit, 2004). This paper will only focus on the latter three hypotheses because the first two
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