"The Royal Commission on Social Policy definition of 'poverty' was not being able to participate in society. That is so different from the popular idea of not having a new pair of shoes or whatever.
"This really supports that idea. If you can't participate in the society that you live in, and for teenagers that is not the whole NZ society or the world society, it's their neighbourhood and their school, if they can't participate in that and their French class is going off to France and on ski trips and holidays, potentially that is actually quite harmful."
Students were surveyed on nine indicators of their families' "material deprivation" including no car, no phone, no computer, unemployment, overcrowding, frequent moves, no holiday in the past year and parents worrying about having enough money for food.
Apart from having no holiday in the past year (22 per cent), the most common indicator of deprivation was people sleeping in a living room or garage (16 per cent). This was far more common for Pacific families (37 per cent), and for Maori (22 per cent) and Asians (17 per cent), than for European families (8 per cent).
Overall 5 per cent of students were classed as being in "material deprivation", usually ticking at least three deprivation indicators, and a further 15 per cent were in "housing deprivation" with significant overcrowding but usually no more than two deprivation indicators.
Half of the Pacific students, 28 per cent of Maori and 15 per cent of Asians, but only 9 per cent of Europeans, fell into one of the two groups in deprivation.
Fleming said the higher rates of depression and smoking among those from materially deprived families in rich areas might be due to better support systems in low-decile schools, or to psychological effects of living among rich families, or both.
"If you are from a household with problems getting food, and other people are hiring a limo to go to the school ball and those sorts of things, potentially there is quite a likelihood of not fitting in and not belonging and being labelled, and that might potentially be depressing," she said.
"The fact that smoking is so much higher for poor kids in rich areas indicates that you might get an effect of being the odd one out, and there is a sort of stigma or labelling and you are almost behaving in a worse way."
The study is online at: http://www.equityhealthj.com/content/15/1/109