The prevalence of cannabis in New Zealand is comparable with that of the United States of America, but it is lower than in Australia and higher than in the Netherlands.
Mental illness The 1998 report on the mental health effects of cannabis by the Health Committee of the 45th Parliament considered the effect of cannabis use on people’s development and the role of cannabis as a trigger for mental illness. That committee observed that the linkages between cannabis use and mental illness were not clearly defined. It noted the view of the Mental Health Research Institute of Victoria that ‘cannabis may contribute to the early onset of psychosis amongst those who are already predisposed to schizophrenia,’ but that scientific evidence had not demonstrated a causal effect; and that permanent brain damage or the development of an amotivational syndrome amongst users was unproven.
Schizophrenia The Royal College of Australian and New Zealand Psychiatrists noted that there is no convincing evidence that cannabis use causes schizophrenia. There appears to be only limited evidence that leads to the hypothesis that cannabis abuse and dependence may increase the risk of schizophrenia. The college notes that the possibility that cannabis is an independent cause of schizophrenia cannot be disproven, but the absence of an increased incidence of schizophrenia over the past 30 years, during which time cannabis use has become much more prevalent, is strongly against such a possibility. However, people with pre-existing psychiatric disorders such as schizophrenia are especially vulnerable to the adverse health effects of cannabis use because cannabis generally provokes relapse and aggravates existing symptoms.
"The critical thing is that many researchers feel now that if people (with schizophrenia) had not smoked marijuana ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ they would not have gone on to develop schizophrenia and that's a really important public health message. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Marijuana Doubles Risk of Schiz. 大麻は精神分裂症のリスクを倍にする
The BBC News reported today on a new research study out of New Zealand that highlights the greatly increased risk of mental illness associated with Marijuana use.
"Smoking cannabis virtually doubles the risk of developing mental illnesses such as schizophrenia, researchers say. The New Zealand scientists said their study suggested this was probably due to chemical changes in the brain which resulted from smoking the drug.
The study, published in the journal Addiction, followed over 1,000 people born in 1977 for 25 years." ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The researchers stated that "The weight of the evidence clearly suggests that the use of cannabis may alter underlying brain chemistry and precipitate the onset of psychosis [and therefore schizophrenia]... in vulnerable individuals," the University of Otago scientists reported in the journal, Addiction.
In another news report on this research study, AAP in Brisbane wrote that in an interview the researchers stated "
"The critical thing is that many researchers feel now that if people (with schizophrenia) had not smoked marijuana ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ they would not have gone on to develop schizophrenia and that's a really important public health message. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ "It's a sufficient trigger in those individuals to tip them over. (But) we actually can't tell who those vulnerable individuals are."