The impact of poverty and social inequality on the health of Scots is clear before children even reach their teenage years, according to a major international report.

Findings from a study covering 42 countries, led by the University of St Andrews, and backed by the World Health Organisation show that young people in Scotland have some of the highest rates of health and social inequality in Europe and North America.

The research contains particularly concerning findings about teenaged girls, with 80 per cent of 15 year olds reporting concerns about school work pressure, a 20 per cent increase since 2006, and the second highest level of any country in the study.

Scottish 15 year old girl are also significantly more likely to report worrying health complaints such as headaches and stomach aches, and this gets worse in the least affluent parts of the country.

However the difference between the health of boys in the 20 per cent most affluent areas and the 20 per cent least affluent is wider than in any other country in the survey.

The Health Behaviour in School-aged Children (HBSC) study, uses new data from surveys carried out about adolescent health, health behaviours and social determinants in 42 countries.

Income also appeared to be having an impact on the health of Scottish boys, who showed the highest level of inequality for multiple health complaints, moderate physical activity, starting smoking and using cannabis, while Scottish girls relationships with their fathers also seemed highly dependent on the levels of deprivation, with those in low income areas less likely to report good relations than those who were less deprived.

However the report includes some positive findings for Scotland. Although alcohol use among teenagers remains a concern - Scotland is one of the countries where 15 year olds are most likely to report having been drunk two or more times - the trend is clearly downwards and has been since 1998.

Meanwhile Scottish 11 year olds are doing better than many of their European counterparts on a number of health indicators. Asked about their satisfaction with life, 92 per cent of boys and 93 per cent of boys reported it was 'high',which is a better proportion than the HBSC average.

Scottish 11-year olds are also on average significantly more likely to eat breakfast daily, brush their teeth twice a day and spend more time with friends outside of school. They were less likely than their international peers to report smoking and drinking, acting like a bully, or worrying about their weight.

But overall, the report contains worrying findings about socioeconomic inequality, which appears to affect health in Scotland in a more marked way, with children from households at different economic extremes reporting markedly different outcomes on a range of health measures from multiple health complaints, relationships with parents, eating healthily, exercise - or the lack of it - and substance misuse.

Dr Joanna Inchley, deputy director of the Child and Adolescent Health Research Unit at St Andrews, said: “The findings provide a better understanding of some of the issues facing young people today. It is encouraging that 11 year olds in Scotland are doing well compared with many of their European counterparts, but we see a clear worsening of health and wellbeing during the adolescent years.

“Particularly concerning is the increase in school-related stress which may be contributing to poorer mental wellbeing especially among 15 year old girls. It is essential that we look at ways of providing support to young people to help them navigate the challenges they face during adolescence.”

Dr Fergus Neville, a researcher at the School of Medicine at the University of St Andrews said it was not clear why 15 year old girls reported high levels of multiple health complaints, but it was concerning. "There is a significant increase. I don't think we know exactly why," he said. He added that further analysis or further surveys might shed light on the reasons, such as whether peer pressure and social media contributed. "Kids in Scotland are more likely to use electronic media to communicate with friends than in other countries, but that can be positive as well as a pressure. More research is needed," he said.

Jamie Hepburn, Minister for Sport, Health Improvement and Mental Health, said: “There are some positive findings in this report, including Scottish 11-year-olds doing better than the international average for life satisfaction, tooth brushing and spending time with friends outside school.

“However, we recognise that there are deeply ingrained health inequalities in Scotland - something which has existed for generations and which will not be solved overnight.

"We need a shift in emphasis from dealing with the consequences to tackling the underlying causes, such as ending poverty, fair wages, supporting families and improving our physical and social environments.

"The Scottish Government is already taking decisive action to address alcohol consumption, reduce smoking rates, encourage active living, healthy eating, and promote positive mental health."

Gerry McCartney, Head of Public Health Observatory, NHS Health Scotland said: “The report highlights the progress we have made in many aspects of health amongst young people in Scotland over time, such as the decrease in consumption of high sugar drinks, but it also highlights the stark inequalities in how healthy children feel themselves to be. Amongst boys, these inequalities are wider than in any other country included in the survey.”