New figures on the number of New Zealanders taking party pills has alarmed doctors.
However, an industry representative is welcoming the uptake of legal highs, claiming party pills are deterring people from using illicit drugs.
Research commissioned by the Ministry of Health shows 20% of people aged 13 to 45 have tried party pills.
Many reported a range of physical and psychological side effects including trouble sleeping, loss of appetite, strange thoughts and irritability.
The survey is the first of four research projects into party pills that are being conducted, before the government considers banning them.
An emergency physician at Christchurch Hospital, Dr Paul Gee says further research is unnecessary, because the dangers are already evident.
But, party pill industry spokesman, Matt Bowden, welcomes the finding, saying the side effects from party pills are little more than a bad hangover. He says party pill deter users from harder drugs.
Respondents were asked about their use of legal party pills containing BZP. One in five said they had tried the pills at some time and one in seven had used them in the past year. Use was greatest among 18 to 24-year-olds, with up to 38% saying they had used them in the last 12 months.
The survey questioned 2,010 people.
