HIGH POT CONSUMPTION INCREASES PSYCHOSIS RATES
CHRISTCHURCH, New Zealand -- Smoking marijuana almost doubles the risk of psychotic mental illness such as schizophrenia, according to recently completed New Zealand research.
The researchers analysed information from 1,055 people born in 1977 who took part in a public health investigation which followed their fortunes over 25 years.
At ages 18, 21 and 25, participants in the Christchurch Health and Development Study were asked about marijuana use.
They were at the same time also assessed on various aspects of their mental health.
The team from the Dunedin-based University of Otago--one of the country's most prestigious medical schools--used the data to determine whether high consumption of marijuana is related to increased rates of psychosis.
The researchers applied statistical models that took into account the possibility that, rather than the drug causing psychosis, mental illness encouraged a greater use of marijuana. They adjusted their results to account for factors such as family history, current mental disorders and illicit substance abuse.
Dr. David Fergusson, who led the study, reported in the journal Addiction:
"Even when all factors were taken into account, there was a clear increase in rates of psychotic symptoms after the start of regular use, with daily users of marijuana having rates that were more than 150% than those of non-users."