Children who find it difficult to talk to their parents are twice as likely to smoke and drink.
By the age of 15, half of young people in Scotland have tried smoking, but the vast majority do not drink, smoke or use cannabis on a regular basis.
And Scottish children are eating more fruit and leading healthier and happier lives than many other youngsters around the world.
How do we know? Because of the Health Behaviour in School-Aged Children (HBSC) survey. Once every four years, the survey is conducted in 43 countries; 2010 is such a year. In Scotland alone, questionnaires went out in January to 6,000 pupils aged 11, 13 and 15 in 370 classes in 316 schools.
Their responses to questions covering everything from bullying to cleaning teeth, eating habits to family life, and friendship to sex have been received by researchers at Edinburgh University's Child and Adolescent Health Research Unit (CAHRU) and the data-entering is under way.
The team hopes to finish this month. Then the data will have to be "cleaned", a process that is unlikely to be completed until late summer.
"We need to look for inconsistencies," says survey manager Winfried van der Sluijs. "If a pupil says they have never had sex and then in the next question tells us they use condoms, we take those responses out."
The first findings, due to be published next Spring, will be more relevant than ever to schools, the researchers predict.
Questions on school life have been expanded significantly this year, with additional questions about how challenging pupils find their school work; whether they think they are treated fairly by teachers; whether they look forward to school; and whether they enjoy being there.
"We know that if young people are engaged in school and their achievement is high, they are generally better off health-wise," explains Dr van der Sluijs.
Headteachers also complete a questionnaire about the ethos of their schools, the sport facilities, whether they participate in the eco-schools programme, the local environment and pupil access to shops and fast food outlets. For the first time, the heads were also asked this year if they used the SHARE sex education programme.
Ultimately, the researchers hope to use their findings to pinpoint what it is about a school that leads to good health in its pupils - both mental and physical.
"It's about building an evidence base showing what policy and practice makes a difference," says Candace Currie, director of CAHRU and international co-ordinator for HBSC.
This year, there is also a "boosted sample" of youngsters living in rural areas, which will allow the researchers to look at health differences between city and countryside.
"The 2006 study threw up some interesting differences in mental health between rural and urban youngsters," says Professor Currie. "The gender difference is the opposite way around, so in remote rural areas we found levels of happiness were highest among girls, whereas in urban areas boys are happier."
A motivational question about alcohol has also been added which, the researchers hope, will allow them to see why young Scots drink.
"Do they do it because they like the feeling? Because it's fun? Because it makes them enjoy the party? Because they want to be liked? Because it makes them feel less depressed?" asks Dr van der Sluijs. "This question should help us find out."
In previous years, questions were asked about mental health, but this time the researchers delve deeper into the way pupils are feeling.
Information will be gathered for the first time about pet ownership, sparked by pupils listing their pets as family members.
"Pets are clearly important members of the family, so it's about interrogating that more and seeing whether young people benefit from having pets and how they feel about them," says Professor Currie. "Most of the evidence suggests pets are good for mental health."
The question will also link into a separate study being carried out in the unit, funded by the Department for Environment, Food and Rural Affairs in England. It aims to develop understanding of the benefits of pet ownership for youngsters and to ascertain how best to teach children about caring for animals.
For a question to be included in the HBSC survey, it is not sufficient for one academic to find it of interest. Questions are honed by a team of international experts. Some are mandatory, so comparison can take place across the countries. Individual countries can add questions relevant to its circumstances and drop any that have yielded little information in the past or become irrelevant.
"We used to ask questions about music preferences to see whether different genres impacted on well-being but we found out very little," says Dr van der Sluijs. "We also removed a question about any drugs pupils had taken other than cannabis, because the response rate was so small."
When the 2010 survey was ready, it was piloted in four Scottish secondary schools and three primaries to ensure the questions were understood by pupils and that they could be answered in the allotted hour. Some were discarded and the questionnaire was piloted again.
The international nature of the study and its longevity - it has been running for 25 years - make it particularly valuable, stresses Professor Currie. "The Scottish HBSC study is part of a larger cross-national study which is conducted in collaboration with the Word Health Organisation. This means we are not just able to say whether or not Scotland is improving, but also where Scotland is relative to other countries."
In the four years from 2002-06, daily fruit consumption in Scotland increased for boys (up from 31 to 36 per cent) and girls (up from 36 to 43 per cent), with the rise particularly marked in 11-year-olds. In 2006, Scotland also leapt up the international rankings for daily fruit consumption, with the second-highest daily rate among 11-year-olds across the 43 countries. (Portugal was first.)
"This was a massive jump up the ranking - in 2002, Scotland had been around the middle of the rankings," she says.
The improving mental health of young people is one of the study's most interesting findings to date, Professor Currie believes. Boys and girls were happier in 2006 than they were in 1994 (52 per cent of boys, up from 39 per cent, and 45 per cent of girls, up from 30 per cent).
"I would be fascinated to know what it is about the lives of children that is changing - whether they feel more empowered, whether people are paying more attention to mental well-being, whether their lives are truly better, whether there is more discussion in families or whether they feel they should be happy, so they say that. We don't know much about this at the moment."
She is curious to see whether there has been any shift in Scottish youngsters' alcohol consumption after indications in 2006 that it could be declining. The country's young people have among the highest rates of alcohol use in Europe and North America, along with other parts of the UK. However, the number of Scottish 15-year-old boys who reported being drunk two or more times dropped from 54 per cent in 1998 to 43 per cent in 2006. For girls, the decline was less marked, but still the figure dropped from 56 per cent to 48 per cent.
"It will be nice to see if that trend continues or if it was just a blip," says Professor Currie.
The increase in fruit and vegetable consumption is among Dr van der Sluijs's favourite findings to come out of HBSC. "It was great to have something positive to report," he says.
This year, he hopes there will be further improvement and in future years he is looking forward to seeing the impact of Curriculum for Excellence and its requirement that health and well-being is taught in all subjects.
"We would expect health-promoting schools, free fruit and the nutrition Act (Schools (Health Promotion and Nutrition) Scotland Act) to have a continued impact and we look forward to seeing what difference Curriculum for Excellence might make.
"If you want to change a culture, you can't just look to schools, but anything we can do, we should do. Using young people's health statistics to perform calculations in maths and using health issues as the basis for discussion and essays in English may well open their eyes."
Professor Currie is also optimistic about the potential impact the new curriculum may have on pupils' health and well-being. "I am quite taken with the assets approach being taken forward by a lot of researchers and policy-makers, which is about looking at what supports good health and well-being," she says.
"It might be to do with building personal coping and resilience or supporting families to support their young people. But it is also apparent in Curriculum for Excellence with the health and well-being strand running through every subject. That's a very positive way forward."
Whether or not the new curriculum is good for pupils' health won't be evident until the results from the 2014 HBSC study are published. In the meantime, schools will have the 2010 results to guide them.
From stress to sex
Key findings in the 2006 Scottish Health Behaviour in School-Aged Children Study
- School work pressures affected nearly a third of young people, particularly age 15 when 34 per cent of boys and 45 per cent of girls reported feeling stressed
- 68 per cent of young people found their classmates kind and helpful
- Nearly a third of 15-year-olds reported that they had had sexual intercourse
- 28 per cent of 15-year-olds and 7 per cent of 13-year-olds had used cannabis
- 25 per cent of boys and 40 per cent of girls reported they felt too fat
- There was a 50 per cent increase in reported dieting among boys since 1990
- Boys fared better than girls on all six mental-health measures
- 29 per cent of boys and 16 per cent of girls met the Scottish Government guidelines on moderate to vigorous physical activity