Alarm bells are being sounded over an increase in the number of people using anti-psychotic drugs.

A new University of Otago study shows the use of anti-psychotic medication has increased by 50 percent - in less than a decade.

It suggests these are often prescribed to help with things like sleep or lowering anxiety.

The Salvation Army's national director of addiction and mental health, Lynette Hutson, says such drugs are fantastic for treating conditions like bipolar and schizophrenia, but not for trouble getting to sleep.

She says this type of medication can have very serious side effects when not used for the correct purpose.

The same study shows highest users of the drugs are European females over the age of 65.

Hutson puts this down to older women being stressed and under a lot of pressure.

She says they live longer than men so often find themselves alone, are financially under pressure, and can be isolated from family.

It's a concerning social dynamic that needs more study, Hudson says.