Depression is on the rise among young people, but antisocial behaviour is down, new research shows

Young people today are more likely to be depressed and to self-harm than they were 10 years ago, but antisocial behaviour and substance use – often thought to go hand-in-hand with mental ill-health – are on the decline.

Instead, poor sleep, obesity and poor body image are becoming more common, suggesting the risk factors associated with mental ill-health might be changing.

Researchers from University College London and the University of Liverpool analysed data from two cohorts of millennials born a decade apart. The younger group was made up of more than 11,000 14-year-olds born across the UK in 2000-01, who are being followed by the Millennium Cohort Study. The older group consisted of just over 5,600 14-year-olds who were born in the Bristol area in 1991-92 and are being followed by Bristol’s Children of the 90s study. The researchers statistically adjusted the data to make the millennium group comparable to the Bristol-born teenagers. They then looked at the prevalence in each group of mental ill-health, substance use, antisocial behaviour, poor sleep patterns and weight problems.

Levels of depression had increased from 9 per cent for young people born in the early 1990s to almost 15 per cent for those born at the turn of the millennium. Rates of self-harm had also risen from 12 per cent to 14 per cent over a decade. While girls from both groups were more likely than boys to be depressed and to self-harm, the rate at which these problems were rising was the same for both genders.

Conversely, the researchers found that antisocial behaviour and substance use, which have been recognised as predicting poor adolescent mental health in previous studies, had decreased over 10 years. Rates of 14-year-olds punching or kicking someone on purpose had dropped from 40 per cent to 28 per cent, and teenagers committing acts of vandalism had decreased from 6 per cent to 2 per cent over a decade.

More than 52 per cent of the those born in the early 1990s had tried alcohol by age 14, compared to less than 44 per cent of those born a decade later. Seven per cent of the 1990s children had smoked cigarettes occasionally in adolescence, compared to just 1 per cent of the millennium group.

The children of the new century tended to sleep fewer hours on week nights, were more likely to be obese and had poorer body image, compared to the children of the 1990s. They were, on average, going to sleep later and waking up earlier. Almost 12 per cent of those born at the turn of the millennium were sleeping less than the recommended eight hours a night, compared to 6 per cent of those born 10 years earlier.

Rates of obesity among young people had almost doubled over a decade from less than 4 per cent to more than 7 per cent. Thirty-three per cent of the group born at the turn of the century perceived themselves as overweight compared to 27 per cent of those born in the early 1990s.

This is thought to be one of the first UK studies to compare data from two different groups of millennials to investigate the changing trends in a range of adolescent mental health and health-related behaviours. The researchers took into account the young people’s personal characteristics and circumstances, including gender, ethnicity and social background, to distinguish actual changes in trends among millennials from differences in the make-up of the two cohorts.

Dr Praveetha Patalay, co-author of the study, said: “The increasing trends of poor sleep, obesity and negative body image might help explain rising mental health difficulties experienced by young people. Where the trends are moving in opposite directions – decreasing substance use and antisocial behaviour – the interpretation becomes more complicated. Understanding the nature of these associations and their dynamic nature over time could be valuable in identifying what the risk factors are for mental health problems, and might help us find potential targets for interventions.

“Striking increases in mental health difficulties, BMI and poor sleep related behaviours highlight an increasing public health challenge. Identifying explanations for these high prevalences and changing trends are key for preventing further poor physical and mental health for future generations of young people.”

Dr Suzanne Gage, co-author, said: “It has seemed for a while that mental health difficulties in young people are on the rise, but this study really highlights the scale at which this increase might be occurring. It’s not just that we’re getting better at measuring depressive symptoms, as identical questions about depressive symptoms were asked in both cohorts. The next step is to understand why these increases are occurring, so young people can be supported better.”

‘Changes in millennial adolescent mental health and health related behaviours over ten years: a population cohort comparison study’ by Dr Praveetha Patalay and Dr Suzanne H Gage is available online on the International Journal of Epidemiology website.

For further information please contact:

Ryan Bradshaw – UCL Centre for Longitudinal Studies
r.bradshaw@ucl.ac.uk
020 7612 6516

Meghan Rainsberry – UCL Centre for Longitudinal Studies
m.rainsberry@ucl.ac.uk
020 7612 6530

Notes for editors:

1. At age 14, young people in both studies answered 13 questions that assess the extent (not true, sometimes true, true) of difficulties in the previous two weeks such as feeling miserable, tired, lonely, crying and hating oneself. A score above an established threshold is indicative of suffering from depression.
2. To be able to make comparisons between the two groups, the researchers first had to make the measures of different health behaviours and outcomes comparable. For example, teens responded to sleep questions in one dataset with an approximate time, and in the other chose a time bracket (e.g. 8pm to 9pm). The researchers converted the times into the same brackets to make the information comparable. Some things like depressive symptoms were assessed using the same questionnaires in both datasets, making comparisons straightforward. Other things the researchers were interested in, like amount of physical activity, were so differently measured between the two datasets that they could not create a comparable enough measure, so these could not be examined in the analysis. A summary of the ‘harmonised’ measures can be found in the full paper.
3. Using sophisticated statistical methods, the researchers went to great lengths to ensure the comparability of the national sample to the Bristol-based sample. One method involved using information on the social background of study members, such as gender, age, ethnicity, mother’s education and mother’s age when giving birth, to match each Children of the 90s (CO90s) study member with the most similar study member in the Millennium Cohort Study (MCS). The other method used information on social background across all individuals to create weights for each study member in MCS, giving higher weights to those most similar to CO90s study members, and lower weights to those least similar.
4. The findings reported in the press release of the statistically adjusted millennium-born national sample were slightly, but not considerably different to those of the national estimates. You can view the nationally represented prevalences of mental health problems and health behaviours of the unadjusted national sample in the research paper.
5. The Millennium Cohort Study is following 19,517 young people born across the UK in 2000-01, building a uniquely detailed portrait of the children of the new century. The last survey of parents and children took place in 2015-16 when the study members were age 14. The study is funded by the Economic and Social Research Council and a consortium of government departments, and managed by the Centre for Longitudinal Studies at the UCL Institute of Education. Visit https://www.cls.ucl.ac.uk/cls-studies/millennium-cohort-study/
6. Established in 1991, Bristol’s Children of the 90s (CO90s), also known as the Avon Longitudinal Study of Parents and Children, charts the lives of 14,500 people born in the former county of Avon between April 1991 and December 1992 as well as the lives of their parents and their children, where applicable. Based at the University of Bristol, CO90s is the most detailed study of its kind in the world, providing a rich resource for the study of the environmental, biological and genetic factors that affect health and development. The study receives its core funding from the UK Medical Research Council, the Wellcome Trust and the University of Bristol and additional support from many other funders for individual projects. http://www.bristol.ac.uk/alspac/
7. The UCL Institute of Education is a world-leading centre for research and teaching in education and social science, ranked number one for education worldwide in the 2014, 2015, 2016 and 2017 QS World University Rankings.  It was awarded the Queen’s Anniversary Prize in 2016.  In 2014, the IOE secured ‘outstanding’ grades from Ofsted on every criterion for its initial teacher training, across primary, secondary and further education programmes.  In the most recent Research Excellence Framework assessment of university research, the IOE was top for ‘research power’ (GPA multiplied by the size of the entry) in education.  Founded in 1902, the Institute currently has more than 8,000 students and 800 staff.  In December 2014 it became a single-faculty school of UCL, called the UCL Institute of Education. ucl.ac.uk/ioe
8. UCL was founded in 1826. We were the first English university established after Oxford and Cambridge, the first to open up university education to those previously excluded from it, and the first to provide systematic teaching of law, architecture and medicine. We are among the world’s top universities, as reflected by performance in a range of international rankings and tables. UCL currently has over 39,000 students from 150 countries and over 12,500 staff. Our annual income is more than £1 billion. ucl.ac.uk | Follow us on Twitter @uclnews | Watch our YouTube channel YouTube.com/UCLTV
9. The University of Liverpool – Associated with nine Nobel Laureates, the University is recognised for its high-quality teaching and research. Our research collaborations extend worldwide and address many of the grand challenges facing humankind today. https://www.liverpool.ac.uk/about/
10. The Economic and Social Research Council (ESRC) is the UK’s largest funder of research on the social and economic questions facing us today. It supports the development and training of the UK’s future social scientists and also funds major studies that provide the infrastructure for research. ESRC-funded research informs policymakers and practitioners and helps make businesses, voluntary bodies and other organisations more effective. The ESRC also works collaboratively with six other UK research councils and Innovate UK to fund cross-disciplinary research and innovation addressing major societal challenges. The ESRC is an independent organisation, established by Royal Charter in 1965, and funded mainly by the Government. esrc.ac.uk