Sixty per cent agreed to go to the next phase of the process, and of those, 70 per cent were referred on to a service.
In the two years Whanganui Police have been doing the survey, they have screened 700 people.
Mr McDonald said the average age of those screened was 26.
Forty per cent were Maori, 20 per cent were stopped for drink driving, and 60 per cent were intoxicated at the time of arrest.
He said 43 per cent of the adults had alcohol disorders, and 75 people were referred to alcohol treatment services.
In total there were 138 referrals.
Information gathered on Whanganui youth showed 30 youth were screened, providing "dramatic results so far", which Mr McDonald called "a little bit disturbing".
Of the youth screened, 40 per cent were developing alcohol use disorders, 31 per cent were in "psychological distress", 22 per cent had a depressive disorder, and 23 per cent had suicidal thoughts or behaviours.
"Those numbers, for me, are just absolutely sad," he said.
"It's an indictment on us - all of us."
Mr McDonald said he had also been looking at how many people in their police cells brought up flags for connection in some way to family violence, and found 80 to 90 per cent did.
"Once this trial's over we're looking at how do we make the referrals through for those family violence issues."
He said the questionnaire took about eight minutes to complete, if the offender agreed to take part.