'Interesting but concerning': NZ antipsychotic use up 50 percent in under a decade

  • 17/08/2018
European women over 65 and Māori men between 25 and 44 are the country's biggest users. Photo credit: Getty

New Zealanders are being prescribed more antipsychotics, despite there being no increase in the country's psychosis rates.

A new University of Otago study, believed to be the first local one of its kind, indicates Kiwis may be using drugs designed to treat conditions like bipolar disorder and schizophrenia to relax or help them sleep.

The prescription of antipsychotic medication has increased in New Zealand by almost 50 percent in less than a decade, according to the study published in the New Zealand Medical Journal.

One in every 36 New Zealanders over the age of 15 were prescribed an antipsychotic drug in 2015, while approximately one in 13 use antidepressants. Antipsychotic usage has increased across all groups and regions according to Ministry of Health prescription data, but the West Coast is the highest-using area.

European women over 65 and Māori men between 25 and 44 are the country's biggest users, with 5.04 percent and 4.77 percent of each group using the drugs respectively.

Māori are more likely to be prescribed antipsychotics than Europeans, while Asians are far less likely to be prescribed them than other ethnicities.

Māori and Pacific men and women were prescribed clozapine, one of the strongest antipsychotics available, at disproportionately high rates. Māori were 2.7 times more likely to be prescribed clozapine than other ethnic groups.

Prof Roger Mulder, a psychiatrist and author of the study, calls the findings "interesting but slightly concerning".

"What we can't say from this study is categorically why people are using these medications, and at what doses," he says.

"There is no evidence rates of psychosis are increasing, so rate increases appear to be related to other issues.

"Antipsychotics are often prescribed 'off-label' for sleep and anxiety issues, so I suspect they may be being used in low doses for anxiety and sleep, and in higher doses for behavioural control."

He says the study shows a "concerning" arbitrariness in how the drugs are distributed across different groups, both geographical and ethnic.

"Antipsychotics have significant adverse effects, and data on long term safety and effectiveness is lacking."

New Zealand's antipsychotic use has grown more dramatically than Australia's, which increased by 36 percent between 2006 and 2014.

The biggest usage increase was for atypical antipsychotics, in particular quetiapine and olanzapine, which made up 82 percent of the prescriptions. Atypical antipsychotics were developed in the 1990s and tend to produce different side effects than traditional antipsychotics developed in the 1960s.