This review is anchored in Rutter and Smith (1)’s seminal monograph, which highlighted an increasing prevalence of youth psychosocial disorders since the mid-20th century. The authors examined the extended transition period from puberty to mature adulthood in the mid-twenties and explored various candidate variables to explain the rising prevalence. Despite their extensive analysis, they found it challenging to draw definitive conclusions. Ultimately, they attributed the trend more to increasing family discord and heightened expectations, particularly related to employment than to other potential factors such as mass media, migration, social disadvantages, unemployment, poor physical health, and declining moral values.

However, the trend of mental health prevenance and burden depends on many factors, e.g., geographical region, socio-demographic status of the region, gender and age group as well as how the prevenance and burden are measured. For example, according to the 2021 Global Burden of Disease Study (2), the prevalence of mental disorders remained relatively stable or decreasing in most countries except for young people 10-19 years in high and high-middle Socio-Demographic Index (SDI) countries prior to the COVID-19 pandemic, which resulted in increases in all age groups across all SDI categories, see Figure 1A . However, the percentage of the total burden attributable to mental disorders, see Figure 1B or mental disorders, self-harm and substance use combined, see Figure 1C increases gradually among those aged 10-34 across most of the SDI categories highlighting the substantial contribution of mental health disorders and self-harm to overall health loss in these populations.

While depression and anxiety can impact people of all ages (3–5), youth aged 10–24 are at a higher risk of experiencing these and other mental disorders (6–9). The pathway to emerging adulthood, from early adolescence to young adulthood, is a time of significant biological, social and personal change that has evolved over generations (10). This period is marked by major life milestones and transitions that coincide with the peak onset of mental disorders (11). Lost productivity at this life stage due to mental illness poses a significant psychosocial and economic burden (12). The imperative to address the mental health needs of young people has been recognised and significant reforms have commenced in some high-income countries to improve mental health service provision for this population (13, 14). These efforts are modest and insufficient in proportion to the scale of need and rapidly rising rates of youth mental ill-health that have been exacerbated by the COVID-19 pandemic (15).Until recently, the evidence for a further increase in youth mental ill-health since the mid-1990s was mixed (16, 17); however, there are increasing indications that this rise is real and alarming in scale (18, 19). Australia’s national survey of mental health recently found that the 12-month prevalence of mental disorders (i.e., anxiety, affective and substance use disorders) among young people had increased by 50% over the past 15 years, disproportionately affecting females (20). The prevalence of depression among young adults in Australia has more than doubled over the past 14 years, according to data from the 2007 and 2020–21 National Survey of Mental Health and Wellbeing (21). The 12-month prevalence of affective disorders, including major depressive disorder, dysthymia, and bipolar disorder, increased significantly from 6.3% to 13.6% among those aged 16–24, and from 7.9% to 11.0% among those aged 25–34, between 2007 and 2020–21 (21). However, according to Liu et al. (22)’ s secondary data analysis of the 2019 Global Burden of Disease study, the annual incidence of anxiety disorders in children and adolescents (10-19 years) decreased by 2.2% from 1990 to 2019, a trend observed primarily before COVID-19 and largely driven by reductions in middle- to low-income countries. There were significant variations in the age-standardised incidence rate (ASIR) and trends among countries. Despite a global decrease in adolescent anxiety disorders over the past 30 years, developed countries continue to see a steady increase in both incidence and disease burden. For example, Portugal had the highest ASIR, while Mexico saw the largest increase. In 2019, Portugal reported the highest number of DALYs (1001.71 million) followed by Ireland (897.80) and Iran (873.64), and India the lowest (212.09 million) (22). Regarding eating disorders among young people, referrals to child and adolescent services in the UK have nearly doubled (23).

Mechanisms underlying this surge remain poorly understood; however, it is likely influenced by a broad range of social and economic changes or “megatrends” (e.g., increasing financial insecurity, family life, educational experiences, and rising health and social inequality) (24). In this review, we focus on the transitional life stage of youth (adolescence and young adulthood). We examine mental health trends relevant to anxiety, depression, psychological distress and wellbeing since the mid-1990s and explore potential explanatory factors associated with prevalence changes.

Of the 89 studies included, 33% (n=29) were based in Europe, 29% (n=26) in North America, 13% (n=12) in the UK, 7% (n=6) in Australia, 6% (n=5) in Asia, 2% (n=2) in New Zealand, 1% (n=1) in each of South America, and Iran, and 7% (n=6) were multinational. Only 4% (n=4) were undertaken with populations from low- and middle-income countries. 79 (89%) were primary studies, of which 60 (76%) were nationally or geographically representative.

Most studies (80%, n=71) reported an increase in at least one outcome related to anxiety, depression, psychological distress, wellbeing or emotional, internalising or somatic symptoms, psychosis, suicidal behaviours/thoughts, eating disorders (ED), Schizophrenia and mood disorders ( Supplementary Table S1 ). The remaining studies reported a decreasing trend (7%, n=6) or no increase (13%, n=12). Trends according to type of mental health problem suggest rising rates of anxiety (15/18 studies), depression (26/37 studies), emotional or internalising problems (20/27 studies), somatic symptoms (8/9 studies), psychological distress (9/14 studies), low mental wellbeing (7/9 studies), suicidal behaviours/thoughts (3/3 studies), Psychosis (1/2 studies), ED (1/1 studies), and Schizophrenia and mood disorders (1/1 studies) ( Supplementary Table S1 ). Methodological differences between studies (e.g., outcome measures, sampling method and sample characteristics) are a probable explanation for the variation in trends.

The degree of increase varied within and across nations. The proportion of young people experiencing anxiety increased by 29–84% in the US (25, 26), 77–164% in Sweden (27, 28), 105% in Australia (20, 29), and 115% in Canada (30). Severe anxiety increased by 86% in the US (31) and high levels of anxiety doubled in Iceland (32). For depressive symptoms or disorder, the percentage of increase was 8%–119% in the US (33–42) and 87% in Australia (43). Severe depression rose by 145% in the US (31), while the change was modest in Finland (+18%) (44). The proportion of young people with emotional or internalising problems increased by 25–79% in the Netherlands and Nordic countries (45–48), 43% in Canada (49), 48% in New Zealand (50), 55–61% in the UK (51, 52), and 10%-64% in Poland (53, 54). For psychological distress, the percentage of increase was modest to large: 43–135% in the UK (55–58), 12–70% in the US (33, 37), and 7%-47% in Ethiopia (59). In the UK, severe psychological distress tripled (58). Somatic symptoms increased by 25–54% in the Netherlands (45, 48), while low wellbeing rose by 119% in the US (31) and 118% in Denmark (60). Rates of suicide increased from 3.6- 7.1 (per 100, 000) in Asian American and Pacific Islander (AAPI) youth in the US (61), ED increased by 5% per month from 2017-2021 (62), and Schizophrenia and mood disorders increased by 4% per month (62).

There are indications that trends have risen since 2011–2016 for psychological distress, low mental wellbeing, and depressive and anxiety symptoms (6, 31, 32, 34, 39, 41, 42, 58, 63–67). Since 2020/the COVID-19 pandemic, rates of psychological distress, anxiety and depressive symptoms have increased further, and mental wellbeing has worsened (56–58, 60, 68–70).

Increasing trends were not observed in Canada, New Zealand, England, China, Netherlands, and Chile for depression; Belgium and Japan for psychological distress; Poland for somatic symptoms; the UK for low wellbeing; and Scotland, Switzerland and Iran for internalising symptoms. However, for each of these locations (except the UK and Canada), only one study was available for the corresponding outcome. Where declining trends were reported, the percentage of decrease was 22% for depression (71) and 6–29% for distress (72, 73).

Trends in relation to gender suggest greater increases among females for anxiety, depression, distress, emotional problems, psychosis, and internalising symptoms (31, 34, 37, 39, 63, 74–78). However, some studies have reported increases for both genders in relation to anxiety, depression and emotional problems (28, 38, 49, 51, 54, 77, 79, 80) or higher increase for males for psychological distress (81), and low mental wellbeing (82). These discrepancies across similar outcomes likely reflect methodological heterogeneity, particularly in terms of outcome measure, which varied across studies. Also, outcomes of this review may not have detected non-specific symptoms (e.g., irritability, anger, and risk-taking) that may represent gender-specific markers of distress in young men (83).

Figure 2 illustrates the trends in youth mental health disorders from 1996 to 2023 (the most recent years of observation in the studies reviewed). The figure shows a declining trend from 1996 to 2015, followed by an increase starting in 2016. The effect of the COVID-19 pandemic (2020-2022) is unclear from this figure at least, and it appears that the increase from 2016 is difficult to explain on that basis.

Social determinants of mental health refer to the structural conditions individuals are exposed to throughout their lives, from conception to death (86). These conditions affect mental health outcomes and contribute to disparities within and between populations. Key factors include income, employment, socioeconomic status, education, food security, housing, social support, discrimination, childhood adversity, neighbourhood conditions, and access to affordable health care (87–89). The likelihood of encountering protective or harmful social determinants is influenced by the distribution of money, power, and resources at global, national, and local levels, shaped by policy choices (86).

The impact of mental health issues is particularly evident among young people. Young people have high rates of self-harm, and suicide is a leading cause of death among them (90, 91). Poor mental health is closely linked to other significant health and developmental concerns, such as educational achievements, substance use and abuse, violence, and reproductive and sexual health (37). Poor mental health can hinder life chances, impacting both lifespan and quality of life. Therefore, improving young people’s mental health by addressing modifiable social risk factors through effective prevention strategies is a critical social justice issue.

Commercial determinants of health, a relatively new area of study, highlight how corporate actions, conditions, and omissions significantly impact health (92). Young people are especially vulnerable to advertisements and celebrity endorsements. For example, marketing electronic nicotine delivery systems and cannabis to young people can activate sensitive and developing pathways in their brains (93). On the positive side, the private sector can enhance public health by providing living wages, paid parental leave, sick leave, and health insurance, all of which contribute to better health outcomes (93). However, as highlighted by critics like Pennington (94) and Monbiot (95), in the context of neoliberal political and economic settings, with minimal regulatory safeguards and weakened central government, the private sector now falls increasingly short in delivering these benefits equitably, leading to rising inequality and growing disparities in health outcomes.

A range of social, environmental, and commercial factors influence the collective life experiences and mental health of young people and their families (93, 96, 97). Ensuring that young people have a healthy environment where they can grow, participate actively in their communities, and pursue goals that honour their uniqueness and dignity is essential (98). However, this is a complex challenge, as meeting basic needs such as safety, education, financial stability, healthy caregivers, and positive life experiences is fundamental to building health and resilience (99, 100).

Adolescence and emerging adulthood have undergone two key maturational shifts: an early onset of puberty and a delayed commencement of independent adulthood (209). This has extended the period of heightened susceptibility to environmental stressors and mental ill-health. This lengthening of adolescence commenced prior to the recorded rise in youth mental ill-health in the 1990s (1). While its impact on more recent trends is unclear, it has converged with educational, labour market and economic shifts (e.g., prolonged years of education; insecure employment, income and housing; and delayed independence) that have contributed to highly precarious pathways to adulthood (113, 159, 163, 167). Emerging adulthood is a heightened period of instability and identity explorations, which have been correlated with anxiety (210). Increasing and cumulative exposure to psychosocial stressors during this period of precarity may have increased the risk of mental ill-health and contributed to deteriorating trends (13, 98, 211). However, the salience and impact of these influences are likely to vary across different cultural settings, as well as in relation to levels of wealth and development around the wealth (212, 213).

Various opinions and theories have emerged to examine and evaluate the candidate causes of negative trends in youth mental health. For example, Twenge (118, 214) and Haidt (143) argue that the rise of social media and increased screen time are the dominant contributors to the deterioration in mental health among young people, suggesting that these factors lead to heightened anxiety, depression, and social isolation. Twenge’s research points to a correlation between the advent of smartphones and a decline in adolescent mental health (215). Haidt (143)’s The Anxious Generation proposes a stronger relationship between the rise in social media use and deteriorating mental health among young people, positing that the increased screen time and social comparison are major contributors to the surge in anxiety and depression. While Haidt (143)’s work has brought significant attention to this issue, it has also been critiqued for potentially overemphasising the role of social media at the expense of other sociocultural and economic factors that may contribute to youth mental health trends. Additionally, the reliance on correlational data in Haidt (143)’s argument, limits the ability to draw definitive conclusions about causality. Thus, support for a causal link between social media usage and increasing depressive symptoms and low wellbeing is limited and requires further investigation using more robust measures of social media use. Despite this, politicians in several jurisdictions have been persuaded to implement age linked restrictions on access to the internet and social media for teenagers (216). Such action can be argued to be misdirected, lacking in nuance and to produce unintended consequences (217–219). This regulatory gap has allowed platforms to prioritize engagement and profit over the well-being of their users, particularly vulnerable populations like young people. Odgers (220) argues that age restrictions and mobile device bans may prove ineffective—or even counterproductive—considering what is known about adolescent behaviour. Regulation of the social media platforms to make them safer would be a more appropriate response.

Wilkinson and Pickett (175)’s work highlights the role of socio-economic inequality, emphasizing how growing disparities and economic stressors exacerbate mental health issues. Focusing on a deeper level, the economic doctrine of neoliberalism, which has dominated the political economy of the globe since the 1980s, can also be hypothesised to be a common force underpinning many of these trends in youth mental health and indeed wider effects on society (86, 221). Neoliberalism, with its promotion of individualism over collectivism and the common good, market deregulation, privatization, a weakened role and respect for government and even democracy, reduced government intervention erosion of the welfare state, creates an environment where young people face heightened economic pressures, social inequalities, and reduced and fragmented health and social safety nets (169, 222). These proposed contributory causes may (223) collectively contribute to the deteriorating trends in youth mental health, however their relative importance is yet to be determined scientifically. To explore whether youth mental health trends reflect surface manifestations of deeper underlying societal changes, new methodologies, including potentially illuminating cross-national comparisons could be employed (108, 224).

Further research is urgently required to understand megatrends impacting mental ill-health in order to quantify their relative effect and estimate their malleability. Subsequently the effective implementation of strategies that target such harmful forces undermining this and other related aspects of public health must be pursued. Firstly, prospective studies utilising comparable sampling methods and measurement approaches are needed to validate trends within and across specific regions and nations, including and especially need to include low- and middle-income countries. This includes using equivalent measures across repeated timepoints (225). A global focus is needed to coordinate national and harmonised surveillance efforts in monitoring trends (226). While the Global Burden of Disease studies provide essential descriptive epidemiology data on incidence, prevalence, mortality, morbidity and disability (227), large longitudinal studies of representative samples are needed to monitor trends and changes within cohorts by assessing young people’s psychosocial development prior to, during and following the developmental stage of emerging adulthood (225, 228). These studies should incorporate comparable measures of potential explanatory factors. By collecting data on a wide range of explanatory factors such as social media usage, economic precarity, and educational pressure, and performing sophisticated multivariate regression analyses, it may be possible to quantify their potential individual and combined effects on mental health outcomes (229).

Causality could be guided by criteria such as temporality, strength and consistency of association, and dose-response relation (230). How these variables interact, and their cumulative effects on mental health require exploration in addition to identifying protective factors. For example, path analysis (231, 232), systems dynamics (233), and structural equation modelling (SEM) (234, 235) model complex relationships between variables to identify direct and indirect pathways influencing mental health. Using advanced statistical software to construct SEM models that include multiple variables and pathways can provide a detailed understanding of how different factors interact to affect mental health (234). Additionally, big data and machine learning can analyze large datasets to identify patterns and predictors of mental health outcomes (236–238). Collecting and analyzing big data from sources such as social media, health records, and surveys, and using machine learning techniques, can uncover trends and predictive factors for youth mental health (237).

Conducting comprehensive literature searches, systematic reviews, and meta-analyses can summarize findings, assess the relative importance of different candidate causes, and identify overall trends and patterns (239). Qualitative research, including in-depth interviews, focus groups, and case studies, with young people, parents, and educators can be used to explore their lived experiences with economic insecurity, educational pressures, and other stressors, and how these impact young people’s mental health (240, 241).

A range of robust approaches (e.g., interrupted time series, cross-cohort comparisons) are needed that contribute to the triangulation of findings and increase confidence in inferring causality (242). This may guide the identification of new at-risk populations and can inform preventive and early intervention strategies where modifiable factors are targeted and their effect on trends are monitored (243, 244). Intervention studies can offer a starting point to implementing and evaluating interventions aimed at addressing identified risk factors and improving mental health outcomes (245, 246). Designing and testing interventions, such as school-based mental health programs or community support initiatives and measuring their effectiveness through stepped wedge, cluster and other forms of randomized controlled trials or other rigorous evaluation methods, can provide more robust evidence for effective strategies (247).

Improving the measurement of cross-sectoral impacts of mental health prevention and treatment costs requires innovative methodologies. By expanding the scope of economic evaluations to include broader cost perspectives and utilizing cost-benefit and return on investment analyses, decision makers can gain valuable insights that extend beyond the healthcare sector (14). Employing methods like Multiple Criteria Decision Analysis (MCDA) can help integrate these economic impacts with other relevant considerations, providing a comprehensive approach for informed decision-making across different government portfolios (248). Moreover, conducting policy analysis to identify key policies related to candidate causes and using statistical methods to assess their impact on youth mental health by comparing outcomes pre- and post-policy implementation, can provide valuable insights (249, 250). There is some scope for limited randomized trials, particularly stepped wedged designs as new policies are introduced sequentially across different communities (251). By integrating these methodologies, researchers can improve the clarity and robustness of their findings, providing a more comprehensive understanding of the relative contributions of different factors to trends in youth mental health. This will give political leaders the opportunity to move beyond opinion, ideology and superficial populist responses.

Improving mental health outcomes requires a multifaceted approach that includes prevention, early intervention, and continuing care. This holistic approach is exemplified in the Mrazek and Haggerty model (85), which highlights prevention, early intervention, and sustained treatment and recovery support (See Figure 3 ).

Prevention, early diagnosis and intervention, and sustained access to evidence-based care have catalysed progress for other non-communicable diseases, leading to significant reductions in the prevalence and impact of conditions such as cardiovascular disease and some forms of cancer (285–287). These fundamental components of health care have not received the same recognition, urgency for deployment, and investment in mental health (288–290). This explains the lack of reduction in the prevalence and burden of mental disorders over the past 25 years (291). Worse still there has been a parallel rise in rates of youth mental ill-health, increased help-seeking and greater need for accessible and safe mental health services among young people (30, 201). However mental health services for young people continue to be all too poorly designed, sparse in coverage and depth, and under-resourced, even in countries that have led youth mental health reform (13). Contributing to these shortcomings are a range of personal and structural barriers. Young people may face personal barriers such as a lack of awareness about available services, mistrust of those services, stigma, misconceptions surrounding mental health, and fears around seeking help (292). Structural barriers include the absence of supportive initiatives within young people’s circles of support (such as family, community, and educational settings), limited-service capacity, and inadequate funding (292). Economic and political factors also present significant barriers to improving the mental health landscape for young people. Unaccountable government policies, harmful and hidden economic orthodoxy, and the impact of unrestrained and unregulated commercial and business activity can be extremely harmful and result in large cohorts of the population being exposed to iatrogenic effects and commercial drivers of mental ill health (293, 294). This is partially recognized but often overlooked in political and economic decision-making. There is a need for mental health impact analyses or statements (295), similar to environmental impact assessments, to be conducted before policies and projects are approved. Privatisation of health care and other economic barriers limit access to mental health services, exacerbate health inequity, and constitute frank discrimination against the mentally ill (296, 297). This scandal results in underfunded mental health programs and insufficient insurance coverage (298).

Strategic investment in both prevention, early intervention, and recovery and improved public health approaches could enable countries to achieve much greater improvements in mental health, save a lot of money and future proof their societies as a result. This includes increased preventive efforts targeting risk factors and determinants of mental illness (e.g., social, economic and environmental), as well as improved provision of evidence-based early intervention that has the capacity to meet the volume of demand (14). Additionally, as discussed in the previous sections, a range of methodological approaches should be utilized to understand the megatrends related to young people’s mental health.

Political will is essential for enacting policies that deliver mental health equity, such as increased funding for mental health research proportional to its share of the burden of disease and its impact on society, implementation of school-based mental health programs, and the establishment of accessible mental health services (294, 299). Political will is directly proportional in a democracy to the level of public activism and demand for reform, which needs to be energised and mobilised (300). Economic stability and growth can also indirectly impact mental health by reducing socio-economic adversity, one of the key contributors to mental health issues particularly among young people (68, 171, 175, 176). Policies aimed at reducing income inequality, improving education systems, and providing health and social safety nets can have positive effects on young people’s mental health (301, 302).

The mounting evidence of increasing youth mental ill-health combined with the persistent neglect of mental health care globally highlights the urgent need for increased action on prevention and early intervention of mental disorders. The scale of this crisis extends beyond the disorders that have been the main focus of this review, as other potentially serious mental illnesses that typically emerge during adolescence and young adulthood, such as eating disorders, have also increased in incidence (303). An immediate call to action was recently declared, with a whole of society approach invited to address growing rates of youth mental ill-health (18). To support this global endeavour, core principles to guide youth mental health care in low-, middle- and high-income countries are available (304) and a global blueprint to transform prevention and early intervention in youth mental health has been developed (305, 306). An urgent and serious public health response to the rising mental health needs of young people is required. This has the capacity to yield massive personal, social, and economic returns. If implemented effectively, major gains seen in other areas of health such as cancer and cardiovascular disease are also possible for youth mental health, and the mental health field and community globally.