PURPOSE: People with severe mental ill-health (SMI) experience profound health inequalities. The Optimizing Wellbeing in Self-isolation study (OWLS) explored the effects of the COVID-19 pandemic restrictions on people with SMI, including how and why their physical and mental health may have changed during the pandemic.METHODS: The OLWS study comprised two surveys and two nested qualitative studies. Of 367 people recruited to the study, 235 expressed interest in taking part in a qualitative interview. In the first qualitative study eighteen interviews were conducted with a purposive sample of participants.RESULTS: We identified six factors which influenced peoples' health, positively and negatively: Staying Physically Active; Maintaining a Balanced and Healthy Diet; Work or Not Working; Daily Routine and Good Sleep; Staying Connected to Family, Friends and the Local Community; and Habits, Addictions and Coping with Anxiety Created by the Pandemic.CONCLUSIONS: Different aspects of lifestyle are highly interconnected. For people with SMI, loss of routine and good sleep, poor diet and lack of exercise can compound each other, leading to a decline in physical and mental health. If people are supported to understand what helps them stay well, they can establish their own frameworks to draw on during difficult times.