The most common brand names for ADHD drugs were Ritalin, Rubifen and Concerta - all containing the active ingredient methylphenidate hydrochloride.
Stimulants such as methylphenidate can also be prescribed to help with fatigue and daytime sleepiness, providing relief to people with Parkinson's disease and narcolepsy.
Researchers say an increasing awareness of the disorder in public and the medical profession - and a willingness to prescribe drugs as a primary option - was behind the growth in prescriptions.
Dr Julia Rucklidge, professor of clinical psychology at the University of Canterbury, said some parents whose children were diagnosed also noticed they had symptoms themselves.
"Now psychiatrists are far more accepting ... that ADHD can exist in adulthood," Rucklidge said.
It's not only over-50s. Prescriptions have risen for all age groups.
More than 183,000 prescriptions were issued in 2016 in total, up 37 per cent on 2013's figures. Half-year figures for 2017 had already hit 100,000 - on track to break 200,000 at year's end.
This would be more than double the 98,000 prescriptions issued in 2005.
Most people received monthly re-writes of their medication scripts. The number of people medicated for ADHD was approximately one-twelfth the number of prescriptions. The number of people diagnosed did not necessarily correspond to the increase in prescriptions.
University of Otago childhood ADHD researcher Dr Dione Healey said significant prescription increases in the last few years nationwide were surprising, given the medical community had been well aware of ADHD for the last 10 or 15 years.
She said the latest international guidelines lowered the threshold for ADHD to be diagnosed, which may have driven the increase in prescriptions.
Healey also urged caution against medicating as a panacea as other methods of treatment, including teacher aides and behavioural management for children and adolescents, were resource-heavy.
"The reality of life is that they require a lot of time and resources that are not available due to finances. So medication is a quicker, easier option."
In Whanganui, prescriptions increased more than 50 per cent between 2013 and 2016.
Clinical director of paediatrics at Whanganui Hospital Dr David Montgomery said he could not conceive why figures would have increased to this level.
"I would be very, very surprised if our prescribing ... has actually gone up more than 50 per cent. That really doesn't sound at all likely," he said.
However, Montgomery said the number of young people receiving the medication was still low compared to international standards, and he didn't have any concerns it was being prescribed too often.
"That's certainly well within the amount of prescribing that would seem reasonable and appropriate."
It's estimated between two and five per cent of New Zealand children have ADHD. This is similar to UK figures, but far lower than the 11 per cent of US children diagnosed.
"It's the most effective treatment for ADHD. Compared with behavioural therapies and other therapies, it's the thing that works best for managing ADHD. You could even ask the question why is the rate of increase so low, [and] should there be more people on it," Montgomery said.
Rucklidge was more sceptical. She said a general medication-heavy approach to mental illness needed to be looked at.
"We've got an increasing number of people with mental illness ... We've got increasing rates of prescriptions ... If the treatment was really working, rates of mental illness should be going down, but it's not.
"If it was cancer, and the rates of cancer were going up with the treatment, wouldn't we all say 'hold on, that's not good?'
"Why aren't we having the same conversations with mental illness?"
