Background: Family carers supporting an individual with psychosis often experience distress associated with caregiving responsibility. However, scarce research evidence exists investigating mental health morbidities in carers of people with psychosis.

Methods: We conducted an online cross-sectional study with adult carers supporting a relative or close friend with psychosis in England. We collected participants’ demographic and health outcome data, including wellbeing (primary outcome) using Warwick-Edinburgh Mental Wellbeing Scale (WEMWBS). We explored the relationships between carers’ characteristics for each outcome in turn, using linear regression. We compared carers’ wellbeing with Health Survey England (HSE 2016) general population data using a meta-analysis.

Findings: Between March 2018 and February 2020, 407 carers across England provided study data. Carers had a mean WEMWBS score of 42∙2 (SD 9∙21), and their overall weighted pooled WEMWBS score was 7∙3 (95% CI -8∙6 to -6∙0, p<0∙01) lower than the HSE sample, indicating carers have poorer mental wellbeing by more than double the minimum clinically important difference of 3 points on WEMWBS. Among all caring relationships, partners had poorer wellbeing compared to parents with lower WEMWBS score (-6∙8, -16∙9 to 3∙3, p=0∙03). Single or lone carers had significantly poorer wellbeing (-3∙6, -5∙6 to -1∙5, p<0∙01) than those who were cohabiting.

Interpretation: Carers of people with psychosis have poorer mental health than non-carers; partners and lone carers most at risk of poor outcomes. Future large-scale prospective studies are needed to develop a predictive model for healthcare clinicians to use and to inform tailored intervention development.

Funding Statement: NIHR Post-Doctoral Research Fellowship.

Declaration of Interests: All authors have no conflicts of interests to declare.

Ethics Approval Statement: The RCT has been reviewed and approved by South Central – Oxford C Research Ethics Committee (Reference: 18/SC/0104) and Health Research Authority Reference: IRAS 240005).