Professor Roger Mulder
The prescription of drugs designed to treat conditions such as bipolar disorder and schizophrenia, and symptoms such as hallucinations and delusions has increased in New Zealand by almost 50 per cent in less than a decade, according to the first local study of its kind.
But instead of indicating an increase in Kiwis with diagnosable psychiatric disorders, it is possible that people are using the prescription drug ‘off-label’ to calm, relax, control or aid their sleep.
The University of Otago, Christchurch study found one in 36 New Zealanders aged over 15 was dispensed an antipsychotic drug in 2015. The highest users are European females aged over 65 (5.04 per cent of that group are using them), then Māori males aged between 25 and 44 (4.77 per cent of that population).
The study features in the latest edition of the New Zealand Medical Journal.
Study author University of Otago, Christchurch psychiatrist Professor Roger Mulder says this first insight into New Zealanders’ use of drugs first prescribed in the 1960s to treat psychiatric conditions is interesting but slightly concerning. It shows usage increased across all groups and parts of the country.
“The Ministry of Health tracks all prescriptions dispensed so we have a very accurate picture of use. What we can’t say from this study is categorically why people are using these medications and at what doses. This is an area that would be useful to explore further. 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.”
Professor Mulder says the increase in use of antipsychotics in New Zealand over less than a decade appears ‘quite steep’. Australia’s usage increased by 36 per cent between 2006 and 2014.
There are two types of antipsychotics – traditional (those developed in the 1960s) and atypical antipsychotics (the next-generation medication developed in the 1990s and with different side-effects), Professor Mulder says. The biggest increase in usage rates were for atypical antipsychotics, particularly quetiapine and olanzapine, which accounted for 82 per cent of these medications prescribed.
The researchers tracked use by ethic group, age and district health board area. They found:
- The number of New Zealanders being prescribed antipsychotic medication has risen to one in 36 New Zealand adults, or 2.81% of the population in 2015. In comparison, antidepressants are used by approximately one in 13 New Zealand adults.
- Slightly more females than males take the medication, with 2.94% of female and 2.67% of male New Zealanders.
- Our rate of antipsychotic use puts us in the middle range for OECD countries. The researchers found antipsychotic use varies greatly among countries.
- The highest rate of antipsychotic use was in European females aged over 65.
- Māori are more likely to be prescribed antipsychotics than European/Other people (3.37% vs 3.15% in 2015).
- The rate of prescribing for Māori is increasing faster than other ethnic groups: 60% in Māori, compared with 52% for Europeans, for example.
- Asian people are far less likely to be prescribed antipsychotics than other ethnicities (0.86% in 2015, compared with 3.1% of Europeans).
- Māori and Pacific males and females were prescribed clozapine, one of the most ‘potent’ of these medications, at rates disproportionately higher than others. For example, Māori were 2.7 times more likely to be prescribed clozapine than other ethnic groups.
- The district health board area with the highest usage was West Coast, and the lowest was Counties Manukau. The West Coast rates of prescription was more than two times higher than that in Counties Manukau.
Professor Mulder says the study shows the prevalence and distribution of use of the medication appears to be somewhat arbitrary. “This arbitrariness in prescribing rates across areas and ethnicity is concerning. Antipsychotics have significant adverse effects, and data on long term safety and effectiveness is lacking,’’ he says.
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