Between 2008 and 2019, we reported positive change relating to mental health stigma and discrimination among the adult population of England, supporting the effectiveness of the Time to Change campaign. Using data from the Attitudes to Mental Illness survey (2008/2009 to 2023), we investigated the extent to which positive changes in stigma were sustained by 2023, 2 years after the programme's end in 2021. We used regression analyses to evaluate trends in outcomes. Measures were of stigma-related knowledge (Mental Health Knowledge Schedule (MAKS)), attitudes (Community Attitudes toward the Mentally Ill scale (CAMI)) and desire for social distance (Reported and Intended Behaviour Scale (RIBS)). We also examined willingness to interact with people based on vignettes of depression and schizophrenia, and attitudes toward workplace discrimination, using data from the British Social Attitudes Survey for comparison. CAMI scores improved between 2008 and 2023 (s.d. 0.24, 95% CI 0.16-0.31), but decreased since 2019 (P = 0.015). After improvements between 2009 and 2019, 2023 MAKS and RIBS scores no longer differed from 2009 scores, indicating decreases in stigma-related knowledge (MAKS scores declined 7.8%; P < 0.001) and willingness to interact (RIBS scores declined by 10.2%; P < 0.001) since 2019. Conversely, comparison with British Social Attitudes Survey data indicated that willingness to interact with people with depression and schizophrenia increased gradually between 2007, 2015 and 2023, and attitudes to workplace discrimination also improved. The lasting positive changes reflect support for non-discrimination and willingness to interact with someone after a sense of familiarity is evoked. Besides the end of Time to Change, interpretations for declines in other outcomes include the COVID-19 pandemic and economic stress.