ObjectivesIsolation precautions (IP) are applied to prevent transmission of pathogens in healthcare settings. Potential negative health outcomes experienced by patients have been previously described but results remain conflicting. We aimed at evaluating the psychological impact of IP in adult patients in isolation using a novel psychological assessment tool.Study designProspective matched cohort study.SettingTertiary care centre in Switzerland.ParticipantsHospitalised patients under IP and non-isolated patients were matched by ward, age and illness severity.Outcome measuresWe measured surrogates of mental and social well-being by using the Pictorial Representation of Illness and Self Measure (PRISM) instrument once during hospitalisation. PRISM is a visual psychometric instrument that has been validated as a quantitative measure of suffering. Smaller distance in self-to-illness separation (SIS) signifies higher importance for a patient.Results156 patients agreed to participate of which 63 were under IP and 93 were matched controls. Median (IQR) duration of isolation was 5 days (2–10). The median SIS (IQR) for perceived inferior nurses’ care was 22.8 (18.5–24.3) and 23.8 (23.3–25.5) for isolated and non-isolated patients, respectively (p<0.001). Similarly, median SIS (IQR) was significantly smaller in isolated than non-isolated patients for avoidance by visitors with 17.5 (7.7–22.0) and 22.2 (21.8–22.6), for loneliness with 7.5 (3.6–16.0) and 18 (10.2–21.6) and for feeling impure with 19 (17.0–21.5) and 21.5 (18.9–22.1), respectively (all p values<0.05).ConclusionsIP to prevent transmission of pathogens may negatively impact mental and social well-being. Measures to alleviate adverse effects of IP should be taken routinely.