In December 2019, clinicians and academics from the disciplines of public health and psychiatry met in Dublin at the Royal College of Surgeons in Ireland (RCSI), to restate their shared commitment to population health. The purpose of this review is to bring our discussion to a wider audience. The meeting could not have been more timely. Six weeks later, the COVID-19 emergency emerged in China and within 12 months it had swept the world. This paper, the contents of which were presented at that meeting in December recommended that future healthcare would be guided more by public health perspectives and informed by an understanding of health economics, population health and the lessons learned by psychiatry in the 20th century. Ultimately two issues are at stake in 21st century healthcare: the sustainability of our healthcare systems and the maintenance of public support for population health. We must plan for the next generation of healthcare. We need to do this now since it is clear that COVID-19 marks the beginning of 21st century medicine.

Climate change poses an existential threat to our planet and our health. We explore the intersections of climate change and mental health which has been under-recognised to date. Climate change can affect mental health directly through the effects of extreme weather events such as heat, drought and flooding, and indirectly through increasing rates of migration and inequality. Vulnerable individuals with neuropsychiatric disorders will be particularly at risk. Emerging evidence is also showing effects of air pollution on brain development. Mitigation efforts related to reducing carbon emissions will have both direct and indirect effects on mental health. A further consideration demonstrated by the COVID-19 pandemic is that the spread of infectious disease can have substantial effects on the mental health of the population. With climate change and biodiversity loss, pandemics could recur in the future with increasing frequency. It is now essential that mental health professionals be equipped as agents for climate action.

COVID-19 has presented society with a public health threat greater than any in living memory, leaving us to question almost every aspect of our society. An ever increasing concern is how we protect the global population from mental illness and whether public mental health policies can achieve this. In this article I reflect on the history of mental health service development, and furthermore on how COVID-19 might impact on the delivery of public mental health strategies into the future.

Cannabis is one of the most widely used recreational drugs among people with clinical psychosis, after nicotine and alcohol. There has been a debate in psychiatry about whether or not we can infer a cause-and-effect relationship between the use of cannabis and psychotic disorders. In this editorial, we first present and critically discuss the evidence to date of the association between heavy cannabis use and psychosis. We argue that while the biological mechanisms underlying individual susceptibility to develop a psychotic disorder following heavy cannabis use are still unknown, heavy cannabis use remains the most modifiable risk factor for the onset of psychotic disorders and for its clinical and functional outcome. This demands a clear move towards both primary and secondary prevention intervention to reduce the impact of heavy cannabis use on the incidence and prevalence of psychotic disorders.

Referrals to Child and Adolescent Mental Health Services (CAMHS) have increased in recent years. Services are already under-resourced and the adverse psychological impact of Covid-19 is likely to increase demand. Accordingly, an understanding of prevalence of mental health (MH) disorders among youth is imperative to help inform and plan services.

Individuals’ mental health and wellbeing are dependent on many social factors including housing, employment, education and adequate nutrition among others. These factors can influence at personal, family and community levels. The interlinked and cumulative impact of these social determinants needs to be ascertained to aid appropriate patient management, as well as to establish prevention and health education programmes. Some of these determinants also have to be recognised at policy level. It is crucial for clinicians to understand the role social determinants play in the genesis and perpetuation of mental and physical illnesses, so that appropriate social interventions can be set in place. Clinicians have a role to play in their clinical practice, as well as advocates for their patients and policy leaders. In order to ensure that health is joined up with other sectors, such as education, employment, judiciary and housing, policy-makers must avoid silos. Every policy must have an impact assessment on physical health and mental health. Policy-makers need to understand scientific evidence and must work with researchers, clinicians, communities and patients to help develop and implement rights-based policies.

This perspective article applies public health principles to improve the physical health of selected populations with mental disorders. Two preventable adverse outcomes, poorer physical health and premature mortality, are described across mental disorders. Evidence of the lifetime effects of adverse childhood experiences and inequalities is presented: these are the ‘causes of the causes’. Seven drivers of physical disorders are illustrated that drive preventable deaths and as doctors, psychiatrists must lead from the front to reverse rising mortality. Evidence supports universal and selective interventions and even the most difficult challenges such as weight gain and opioid misuse are an opportunity for psychiatry to engage with individual patients and their organisations, public health colleagues, health systems and beyond. Interventions complement and do not replace existing clinical practices that reduce self-harm and prevent suicide. Mental health teams already do most of the work in this arena, and the case is made to refocus on physical health with task sharing. The top 10 recommendations within a personalised medicine framework are listed in this paper as a starting point.

Mental health issues are fast becoming one of society’s greatest health challenges with evidence of higher levels of illness and strain on psychiatric services. The reasons for this trend of increasing mental health problems across the population are complex and there is an urgent need to research and deliver effective public mental health strategies. In this perspective piece we argue that psychiatrists and public health physicians have unique knowledge and perspectives on population mental health. The development of interdisciplinary initiatives and training posts would result in clinicians with expertise to drive forward public mental health strategies. Focused and sustained advocacy and collaboration are necessary for prioritisation of public mental health on policymakers’ agendas.

In 2010, Ireland found itself at the eye of an international storm as a network of head shops emerged selling new psychoactive substances (NPS) and Irish youth rapidly became the heaviest users of NPS in Europe. Within months, the Irish government enacted novel legislation, which has since been copied by other countries, which effectively stopped the head shops selling NPS. Critics of this policy argued that it could cause harms to escalate. A number of separate studies indicate that a range of drug-related harms increased amongst Irish youth during the period of head shop expansion. Within months of their closure, health harms began to decline. NPS-related addiction treatment episodes reduced and admissions to both psychiatric and general hospitals related to any drug problem began to fall. Population use underwent sustained decline. Consequently, the closure of head shops can be viewed as a success in terms of public health.

This article provides an overview of the public health approach to suicide in Ireland. The authors provide detail on the current suicide prevention strategy in Ireland, Connecting for Life, which is a whole-of-government, systemic, multicomponent national strategy. As the strategy enters its final extended phase of implementation over the period 2020–2024, the public health elements of Connecting for Life are presented, including the population level and more targeted approaches. The findings of an interim review of the strategy are discussed, in addition to the local and national implementation structures which are in place to assist implementation and monitoring of the strategy.

In 2012, the Irish Department of Health published a strategy in relation to alcohol and flagged that a Public Health (Alcohol) Act would be pursued through the Houses of the Oireachtas. This Public Health (Alcohol) Act was intended to reduce alcohol consumption and the harms caused by the misuse of alcohol. The act includes various means for this purpose, including introducing statutory minimum prices on alcohol, restricting alcohol advertising, addition of warning labels to alcohol products, and reducing the visibility of alcohol products in retail outlets. This perspective piece aims to provide an account of how this public health alcohol policy has been implemented in Ireland. The strategy relied in a major way on the World Health Organisation framework for alcohol policy. It took 3 years from the launch of that strategy to get the Public Health (Alcohol) Bill published, in December 2015. It took almost another 3 years to get the Public Health (Alcohol) Act passed by the Houses of the Oireachtas, in October 2018. The Act was signed into law by the President of Ireland in November 2018, and it’s implementation has commenced in the last few years. This perspective piece highlights the complexities and challenges of implementing legislation related to public health policy, but also demonstrates that real action can occur with advocacy from public health clinicians and key stakeholders.