The Psychosis Spectrum in Adolescents: An Empirical Study of Paranoid Thinking, and a Review Comparing Neuropsychological Characteristics and Longitudinal Outcomes Between Early- Versus Adult-Onset Psychosis

Psychosis involves various symptoms, including unusual beliefs and sensory experiences, and reduced motivation/interest. Psychosis onset before age 18 is classified as ‘early-onset’. ‘Adult-onset’ psychosis defines psychosis onset after age 18. Typically, early-onset psychosis has been considered more severe than adult-onset, and as involving poorer long-term outcomes. Paranoia often occurs with psychosis, and involves thoughts that others are intentionally trying to harm you, in the absence of supporting evidence. Paranoid thoughts commonly occur amongst general populations of teenagers, but are poorly understood.

Section 1 was a systematic review of studies comparing cognition (e.g., memory, problem-solving, IQ) and long-term outcomes between individuals with early-onset versus adult-onset psychosis. A meta-analysis compared overall IQ differences between the groups. Studies found that adult-onset psychosis showed better executive functioning (supports planning, problem-solving, organisation), verbal and performance IQ compared to early-onset. Processing speed and rates of suicide over time were similar across early-onset versus adult-onset. However, these findings require replication through further research. Meta-analysis found no significant IQ differences between early-onset versus adult-onset. Findings for all other areas of cognition and long-term outcomes varied between studies.

Section 2 was an empirical study focussed on understanding predictors of paranoia amongst a general population of teenagers from five UK schools. 404 16-19-year-olds completed questionnaires about perceived inequality, beliefs about the self/others, sense of belonging, rejection sensitivity (RS), intolerance of uncertainty (IOU), peer victimisation (i.e., mistreatment from peers), paranoia, and social anxiety.

Negative beliefs about others were linked to paranoia and social anxiety, but sense of belonging nor positive beliefs about others were not. Higher negative-self beliefs, RS, IOU, and lower positive-self beliefs were linked to social anxiety, not paranoia. Depression and peer victimisation were only linked to paranoia. Interplay between RS and IOU did not explain the link between peer victimisation and paranoia, which requires further research.