This thesis explored how psychosis stigma affects the psychological wellbeing of young people at risk of psychosis and people with psychosis. The efficacy of psychosocial methods to reduce stigma in young people were explored. Multiple methods were used including qualitative, cross sectional, longitudinal and a randomsied controlled trial. Chapter 1 included a comprehensive review of the literature on stigma. Chapter 2 provided a review of the methodology used throughout the thesis. Study 1 (Chapter 3) examined the subjective experience of psychosis using Interpretative Phenomenological Analysis. Three super ordinate themes of judgment, disclosure and psychological distress were identified. Analysis of the data suggested a directional relationship between the themes with societal judgments, affecting issues of disclosure and judgment and disclosure issues increasing psychological distress. Possible exits from distress were suggested. Study 2 (Chapter 4) explored relationships between internalised stereotypes (IS) of psychosis and emotional dysfunction in people at risk of developing psychosis. Correlational analyses indicated significant relationships between IS, depression, social anxiety, and distress. Multiple regression analyses indicated that baseline IS predicted depression at follow up. Results suggested that IS may increase psychological distress and in particular depression in young people at risk of psychosis. Study 3 (Chapter 5) explored relationships between IS and emotional dysfunction in people with psychosis not taking antipsychotic medication. The findings revealed significant positive relationships between IS, depression and social anxiety. Multiple regression analysis suggested that baseline IS predicted depression at follow-up but this did not remain significant when controlling for baseline depression. These results replicate the findings of previous research carried out in other psychosis populations. Study 4 (Chapter 6) explored differences in the level of IS and the strength of relationship between IS and emotional dysfunction, between those at risk of psychosis and those with psychosis. Results of the cross sectional analysis indicated no significant differences between the groups on level of IS or on the strength of correlation between IS and emotional dysfunction. This interesting find suggests that young people at risk of psychosis may be internalising stereotypes early and before official diagnostic labels are applied. Study 5 (Chapter 7) examined the efficacy of internet based anti-stigma interventions for young people. Results indicated a non-significant trend towards reduction in stigma, immediately post intervention for the contact and psychosocial educational conditions, however superiority over control was not demonstrated. Findings indicated that internet based interventions for this group should be brief and ensure maximum engagement. This thesis has demonstrated that stigma affects the wellbeing of people whose experiences exist along the psychosis continuum. Research is required to better understand the feasibility and efficacy of clinical and mass media interventions to reduce the negative effects of stigma in people with psychosis and the public.