The Toronto Adolescent and Youth Cohort Study: Study Design and Early Data Related to Psychosis Spectrum Symptoms, Functioning, and Suicidality

Psychosis spectrum symptoms (PSS) occur in a sizeable percentage of youth, and are associated with poorer cognitive performance, functioning, and suicidality (i.e., suicidal thoughts and behaviors). PSS may occur more frequently in youth already experiencing other mental illness, but the antecedents are not well-known. The Toronto Adolescent and Youth (TAY) Cohort study aims to characterize developmental trajectories in youth with mental illness and understand associations with PSS, functioning, and suicidality. The TAY Cohort study is a longitudinal cohort study that aims to assess 1,500 youth (11-24 years of age) presenting to tertiary care. The present manuscript describes the extensive diagnostic and clinical characterization of psychopathology, substance use, functioning, suicidality, and health service utilization in these youths, with follow-up every 6 months over 5 years, including early baseline data. 417 participants were enrolled between May 4, 2021 and February 2, 2023. Participants met diagnostic criteria for an average of 3.5 psychiatric diagnoses, most frequently anxiety and depressive disorders. 49.2% of participants met a pre-established threshold for PSS, and exhibited higher rates of functional impairment, internalizing and externalizing symptoms, and suicidality compared with non-PSS participants. Initial findings from the TAY Cohort study demonstrate the feasibility of extensive clinical phenotyping in mental health help-seeking youth. PSS prevalence is much higher than in community-based studies. Our early data support the critical need to better understand longitudinal trajectories of clinical youth cohorts in relation to psychosis risk, functioning, and suicidality.