AbstractBackgroundSmoking is the largest single contributor to poor physical health and increased mortality in people with serious mental illnesses. The aim of the study was to investigate the utility of electronic cigarettes (e-cigarettes) as a harm reduction intervention in this population.MethodFifty tobacco smokers with a psychotic disorder were enrolled onto a 24-week pilot study (ClinicalTrials.gov: NCT02212041) investigating the efficacy of a 6-week free e-cigarette intervention to reduce smoking. Cigarette and e-cigarette use was self-reported at weekly visits, and verified using carbon monoxide tests. Psychopathology, e-cigarette acceptability and adverse effects were assessed using standardised scales.ResultsThere was a significant (⩾50%) reduction in cigarettes consumed per day between baseline and week 6 [F_{(2.596,116.800)} = 25.878, p < 0.001], and e-cigarette use was stable during this period [F_{(2.932,46.504)} = 2.023, p = 0.115]. These changes were verified by significant carbon monoxide reductions between these time points [F_{(3.335,126.633)} = 5.063, p = 0.002].ConclusionsThe provision of e-cigarettes is a potentially useful harm reduction intervention in smokers with a psychotic disorder.