Due to the chronic relapsing nature of mental disorders and increased life expectancy, the societal burden of these non-communicable diseases will increase even further. Treatments for mental disorders are available, but their effect is limited due to patients’ (genetic) heterogeneity, low treatment compliance and frequent side effects. Only one-third of the patients respond to treatment. Today, medication selection in psychiatry relies on a trial-and-error approach based mainly on physicians’ experience. Pharmacogenetic testing enables assessing person-specific genetic factors that predict clinical response and side effects. Recent studies show that genotyping of drug-metabolizing enzymes can increase the effectiveness of treatment, which could benefit millions of patients. PSY-PGx is the first initiative to propose a large-scale non-industry sponsored clinical study that demonstrates the clinical benefits and potential of implementing pharmacogenetics for psychiatric patients in existing medical settings. To this end 1) available biobank data (www.biobankki.fi, www.ukbiobank.ac.uk), with the aid of AI, will be searched for pharmacogenetics that influence medication response. This information is used to 2) perform a clinical trial that will be the first large international, multicenter clinical trial on using pharmacogenetic-based treatment personalization in real-life psychiatric care for depressed, anxiety or psychotic disorder patients. All data is combined with AI to set-up an algorithm for personalizing medication prescription for psychiatric patients that reduces side effects and increases effectiveness of pharmacotherapy. PSY-PGx will thus deliver a new model of care for sustainable healthcare systems and reduce the suffering of psychiatric patients.