The SARS-CoV-2 (CoVid-19) pandemic has highlighted the central importance of social determinants of health to human welfare. This highly infectious disease has followed well-recognised patterns whereby people who have poor personal and financial resources are most at risk of contracting the disease, and of experiencing poor outcomes, including death, when they do. Unless action is taken across the world, the long-term socio-economic consequences of the pandemic are likely to lead to a wave of mental illness, as it is now well established that disorders such as psychosis are strongly associated with childhood exposure to disadvantage, and that the association is probably causal. There is good reason to believe that action to reduce inequality will mitigate this risk. Inequalities apply both within nations and between nations. Disadvantage aggregates in such a way that disasters such as the Beirut Harbour explosion of August 2020 particularly affect populations already struggling with multiple health challenges. Psychiatrists should take a role in promoting better public mental health by emphasising the relationship between social injustice and poor mental health to employers, policy makers and the public.