As of 2015, with the adoption of the Sustainable Development Goals (SDGs), the United Nations has a new roadmap for development that will guide global and national agendas for the next 15 years: a historic moment of global consensus and collaboration, and a watershed moment for mental health. For the first time, mental health was explicitly represented as an essential component of the United Nations' official development agenda. This is a major achievement that has taken decades of unrelenting advocacy. It is a breakthrough in global development to acknowledge that addressing mental health can improve a broad range of health and development outcomes, including better growth outcomes for infants of mothers with depression, improved rates of HIV/AIDS prevention and reduced effects of alcoholism on families and communities. This milestone reflects remarkable progress in terms of overcoming structural, political and social barriers. We are witnessing a profound culture change that is bringing mental health to the global development stage.

Initially, the argument was that mental disorders were not prevalent globally, a myth that the Global Burden of Disease debunked in 1993 and has continued to disprove with increasing certainty and vigour (Whiteford et al, Reference Whiteford, Ferrari and Degenhardt2015). The next barrier was the perception that mental disorders could not be treated in very low-resource settings or that trying to do so was a waste of resources. High quality studies on the effectiveness of evidence-based mental health interventions, even in the most low-resource environments, have been conducted over the past decade (Bolton et al, Reference Bolton, Bass and Neugebauer2003; Rahman et al, Reference Rahman, Malik and Sikander2008; Bass et al, Reference Bass, Annan and Mcivor Murray2013; De Silva & Ryan, Reference De Silva and Ryan2016) and, increasingly, studies on the cost-effectiveness of mental health treatments highlight the economic value of treating and preventing mental disorders (Chisholm et al, Reference Chisholm, Sweeny and Sheehan2016; Petersen et al, Reference Petersen, Evans-Lacko and Semrau2016).

Since 2011, the three largest funders of mental health research in low- and middle-income countries – Grand Challenges Canada, the UK Department for International Development and the USA's National Institute of Mental Health – have invested an estimated US$79.3 million in global mental health research and training (Collins & Saxena, Reference Collins and Saxena2016). With this increasing momentum in global mental health, the task of building mental health services and integrating them within the primary care services of countries is slowly advancing, supported by resources and recommendations developed by the World Health Organization, including the World Mental Health Atlas (WHO, 2015), the 2001 World Health Report (WHO, 2001), and the Mental Health Gap Action Programme and accompanying Intervention Guide (WHO, 2010).

Successful countries that have been pioneers in integrating mental health into national health policy have shown the feasibility and importance of comprehensively addressing mental health. Uganda, for example, effectively introduced a mental health unit and a mental health coordinator into the Ministry of Health, and integrated mental health into the country's first National Health Policy in 1999 (Baingana & Mangen, Reference Baingana and Mangen2011). This allowed for changes in services to be measured, leading to improved access and quality of mental health services. Mental health was also a fundamental component of the rebuilding of Afghanistan's healthcare system after the fall of the Taliban (Ventevogel et al, Reference Ventevogel, Van De Put and Faiz2012).

In the context of this increasing evidence of the importance and feasibility of addressing mental health globally, as 2015 approached and the Millennium Development Goals were set to expire, an international initiative of global mental health leaders – called FundaMentalSDGs – along with other actors, came together to advocate for the inclusion of mental health in the SDGs (Detlev, Reference Detlev2015). Over 2 years they wrote letters, met with Ministers of Health, attended open United Nations meetings, wrote publications and lobbied strongly when mental health was not included in the wording of the first draft of the SDGs. Ultimately, the advocacy paid off and mental health is now explicitly included in the SDGs. Goal 3 of the 17 SDGs is to ‘Ensure healthy lives and promote well-being for all at all ages’. Each of the 17 SDGs includes a number of targets, and the fourth target for goal 3 explicitly mentions mental health: ‘By 2030, reduce by one third premature mortality from non-communicable diseases through prevention and treatment and promote mental health and well-being.’ Two other targets within goal 3 also mention aspects of mental health: target 5 on substance misuse and target 8 on access to quality, essential healthcare services, which can be interpreted to include mental health. Four other goals out of the 17 SDGs – goals 4, 8, 10 and 11 – include specific mention of inclusion of people with disabilities, an important step for people who suffer from mental disorders.

Global mental health achieved a major victory by being included in the SDGs – but it is just the beginning. The success of mental health in the SDGs relies on the ability for the mental health targets to be measured. Each target within each goal in the SDGs includes at least one indicator to measure progress towards that target. There are no true indicators of core mental disorders; however, there are two indicators that are closely tied to mental illness: one within target 3.4, suicide mortality rate, and one within target 3.5, coverage of treatment interventions for substance use disorders. Although a reduction of these two indicators would be a significant advance for mental health globally, the majority of the burden of mental ill health is not included in these indicators and will therefore be unmeasured. Mental disorders are the leading cause of the non-fatal disease burden globally, and anxiety and depressive disorders account for over half of that burden, whereas alcohol use disorders account for approximately 10% (Whiteford et al, Reference Whiteford, Ferrari and Degenhardt2015). An indicator that was recommended by FundaMentalSDGs included people with depression (the proportion who are using services) but was not included in the SDG indicator framework. Ultimately, the indicators will substantially affect the extent to which health systems incorporate the mental health target into their development programmes.

The explicit inclusion of mental health in the SDGs is an invitation for mental health workers to collaborate with other players who are working to influence global health and development. The task is now for the global mental health community to actively work within health systems, and other sectors, to integrate mental health interventions within the context of programmes aimed at other goals and targets, and to measure the impact on those other goals and targets when mental health is addressed. We can already see examples of this: When HIV/AIDS programmes began treating those patients with HIV/AIDS and depression with antidepressants, the odds of a person adhering were 83% better if they were treated for depression (Sin & DiMatteo, Reference Sin and Dimatteo2014). Another example is that when a maternal depression intervention, called the Thinking Healthy Programme, was integrated into maternal and child health services in Pakistan, immunisation rates improved and contraceptive use increased in the intervention group (Rahman et al, Reference Rahman, Malik and Sikander2008). More synergistic effects like these, especially across sectors, should be explored through integrated mental health services and measurement. For example, can interventions that treat mental disorders like depression and anxiety bolster the effects of programmes aimed at environmental sustainability? Can a mental health intervention for at-risk youth influence the targets of the SDG for decent work and economic growth? Such pointed research and evaluation can demonstrate to governments that progress on other SDGs is severely hampered without addressing mental health. Ultimately, it is crucial that the governments of countries are convinced of mental health as a development priority, because SDGs will be monitored and adapted to local contexts by domestic governments.

This kind of integrative mental health evaluation within the development agenda requires resources, and mental health remains constrained by insufficient funding. A strategy for achieving the required funding for global mental health should be multi-pronged, with both short-term and longer-term goals. Ultimately, the global mental health community should aim to provide the evidence and convince all stakeholders of the fundamental role of mental health within health and global development. In the medium term, we can work to identify key partners that could easily be aligned with mental health priorities. At the same time, given the current status of mental health in the global development community, we need to identify the messages that funders and governments are already attuned to and propose mental health programmes with those messages in mind.

In sum, although the inclusion of mental health in the SDGs represents a significant advance for mental health and the global development agenda, it is still merely an invitation for mental health to play a greater role. Continued advocacy for mental health is required for the progress over the past decades to be sustained. The Lancet and its sister journal The Lancet Psychiatry have assembled leaders from around the world to prepare a Commission on Global Mental Health to be published on World Mental Health Day in 2017, marking the 10th anniversary of the first Lancet series. This Commission's work will show the centrality of mental health to the SDGs, both in terms of the specific health goal as well as the other relevant SDGs. They will look to a wide variety of stakeholders to identify innovations and promising approaches to transform the landscape and catalyse the field of global mental health, including advances in implementation research, novel ways to deliver mental health treatments, the use of technology and addressing the social determinants of mental health. Mental health in the SDGs is an indication of a new dawn for the global development agenda, but it will require an integrated, inter-sectoral scientific collaboration to bring to light the true importance of mental health for sustainable global development.