Meth use linked to schizophrenia risk

Meth use linked to schizophrenia risk

People who are heavy users of methamphetamines may have a higher risk of developing schizophrenia, new Toronto research suggests.

The study — the largest of its kind, and the first to show such a link — looked at whether people who heavily use drugs, including methamphetamines, cocaine, cannabis, opioids and alcohol, are more likely to develop schizophrenia than the general population.

It found that people who are hospitalized for methamphetamine dependence were between 1.5 and 3 times more likely to develop the disorder than patients who heavily used alcohol, cocaine or opioid drugs.

“There is something uniquely harmful, it seems, with methamphetamines and its relationship with schizophrenia,” said Russell Callaghan, the study’s lead author and research scientist at the Centre for Addiction and Mental Health.

The researchers also found a link between heavy cannabis use and a higher risk of schizophrenia. Previous studies have shown marijuana can trigger psychosis in vulnerable individuals.

Researchers analyzed California hospital admissions data from 1990 to 2000 and compared groups of patients who were admitted for drug abuse or dependence, along with a control group of patients. They looked to see whether there were any differences in subsequent readmissions for diagnoses of schizophrenia.

Patients who used more than one drug or who had previously been admitted for psychosis were excluded from the study.

Callaghan said the study clearly demonstrates a link between methamphetamine use and schizophrenia, but warns more research is needed to more fully understand the association.

Scientists believe repeated use of stimulants, such as methamphetamines and cannabis, can disturb how the brain responds to dopamine — an important neurotransmitter involved in mood, memory and reward-seeking behaviour — which can then trigger persistent psychosis, or schizophrenia.

The study was published online Tuesday in the American Journal of Psychiatry.

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