Table 1 Description of outcome variables and socioeconomic deprivation measures

Depressive symptoms (10 items)

Students’ depressive symptoms were assessed by the Reynolds Adolescent Depression Scale – Short Form (Mean 19.56, SE 0.07, Range 10–40, Cronbach’s alpha 0.90). This is a well validated 10-item questionnaire that measures depressive symptoms among adolescents. Based on previous analyses, students with a score greater than 28 were classified as having clinically significant depressive symptoms [34, 35].

Overweight/Obese

Anthropometric measures were taken by trained research staff following standardized procedures and protocols. Height was measured using a portable stadiometer (Seca model 214, Seca, Hamburg, Germany) to the nearest 0.1 cm. Weight was measured using digital scales (Health-o-meter model 349KLX, Health-o-meter, Bridgeview, IL) to 0.1 kg. Body mass index was calculated by dividing weight (kg) by height (m) squared. Students were classified as overweight/obese based on age and sex-specific BMI definitions as recommended by the International Obesity TaskForce [36].

Weekly cigarette smoking

Weekly cigarette smoking was assessed by two questions: “Have you ever smoked a whole cigarette?” with response options “yes”; “no”; and “How often do you smoke cigarettes now?” with response options: “Never – I don’t smoke now”; “Occasionally”; “Once or twice a month”; “Once or twice a week”; “Most days”; and, “Daily”. Students who reported smoking weekly or more often were classified as weekly cigarette smoking”.

Household goods: car/ telephone/ computer

To assess household goods, students were asked: “In your home how many of the following things are there?”, with response options:”A car that goes”;”A telephone that works”; “A computer/ laptop” with response options “None”; “One”; “Two”; “Three or more”. Students who reported no car, no telephone or no computer were classified into the “No car’, “No telephone” and “No computer” groups respectively.

Parents worry about having enough money for food

Students were asked “Do your parents, or the people who act as your parents, every worry about not having enough money to buy food?” with the response options “Never”, “Occasionally”, “Sometimes”, “Often” and “All the time”. Students who responded “Often” and “All the time” were classified as “Parents worry about having enough money for food”.

More than 2 people per bedroom

Overcrowding was calculated from the responses to two questions: “How many bedrooms are there where you live?” with response options “None”, “1”, “2”…”10”, “more than 10” and “How many people, including you, usually live in your main or only home?”. Students who reported more than two people per bedroom were classified as “More than 2 people per bedroom”.

No family holiday in last 12 months

Information on Family holidays was obtained by asking the question: “During the past 12 months, how many times did you travel away on holiday with your family?” with response options: “Not at all”; “Once”; “Twice”; and, “Three or more times”. Students who reported “Not at all” were classified as “No family holiday in last 12 months”.

Moved homes 2 or more times in the last 12 months

Moving frequently was assessed by the question: “In the last 12 months, how many times have you moved homes?” with response options: “I haven’t moved homes”; “I have moved once”; “I have moved two times”;”I have moved three or more times”. Students who responded two or more times were classified as “Moved homes 2 or more times in the last 12 months”.

Living room or garage used as bedrooms

Lack of bedrooms was assessed by the question: “What places are used as bedrooms in your home? (You can choose as many as you need)” with the “yes” or ‘no” response options to the following choices: “Living room”; “Garage”; “Caravan”; “Other rooms that aren’t bedrooms”; and, “None of these”. Students who reported a living room or garage used as bedrooms were classified as ‘Living room or garage used as bedrooms”.

No parent at home with full-time employment

Parental employment was explored through two questions, separately for mothers and fathers: “Does your dad (or someone who acts as your dad) have a job?”, with response options: “Yes – full time”; “Yes – part time”; “No”; ‘I don’t know”; and, ‘Does not apply to me”. Students were also asked who they lived with in their home, with response options including their mother and/ or father. Students who responded that both parents were not in fulltime employment or that the single parent they lived with was not full-time employment were classified as having “No parent at home with full-time employment”.