"One great quote that a young woman gave us following her fifth bout of chlamydia was 'when I drink, I don't think'. There's that sense of being bomb-proof and in the moment."
The study, by the University of Auckland's Dr Terryann Clark who recently joined Manaia PHO, looked at the experiences of more than 27,000 secondary school students.
It also indicated young people today are more likely to delay having sex, which Dr Bollen called "good news" But there were those who were peer-pressured to not use protection.
"There are staunch communities of blokes that just don't like using condoms. We can do all our work with the females but it's harder to get the guys - they think they know what's what," Dr Clark said.
Teenage pregnancy was also often not unintended.
"Lots of young women are longing to become parents," she said. "They want somebody that will love them. Many of our young people have not had affirmation at school or in families. When they see their friends with a cute little baby ... there is a longing to join that club."
She said it was also not unusual to see 16 to 18-year-old men who wanted to be fathers because "there's a prestige in fathering children".
Part of the solution was a holistic approach including re-engaging young people with education, getting them involved with groups and clubs and showing them there were many options for the future.
Dr Bollen said she did not want to denigrate teenage mothers, many of whom did an "amazing" job.
Octane Youth Health has been running since 2014 alongside Whangarei Youth Space and offers a free full-spectrum health service for 12 to 18-year-olds - not just sexual health services. Text 021 376 729 or drop in at 75 Bank St.