We screened 216 patients in a retrospective observational investigator-initiated study, of whom 45.37% patients (n=98) were retained after the inclusion criteria were applied. These patients had been prescribed paliperidone palmitate long-acting injection (PPLAI) with diagnoses of schizophrenia, schizoaffective disorder and bipolar affective disorder. We investigated whether PPLAI has an effect on the frequency and length of admissions to mental health inpatient units, the number of contacts with Crisis Resolution Home Treatment Teams (CRHTT) and frequency of home visits by the CRHTT per patient, over 6 years, split using a ‘mirror image’ method. In total, 85% of patients continued PPLAI for 1 year, 60% for 2 years and 47% for 3 years. In the sample of patients who continued with PPLAI for 3 years (n=48), the mean number of hospital admissions decreased from 1.03 to 0.35 per patient (P=0.001). The mean number of bed days decreased significantly from 53 to 24 bed days (P=0.0001). The median values showed similar significant differences. There were numerical differences but nonsignificant results between CRHTT’s number of contacts and length of episodes across the study period. Our results indicate that PPLAI has been shown to be effective in the reduction of hospital admissions, relapse rates and length of inpatient stay.