Abstract
BACKGROUND: The early phases of severe mental disorders are often diagnostically challenging, with frequent diagnostic shifts over time. Few studies have combined detailed baseline diagnostic assessment with long-term follow-up to examine both diagnostic and social development. METHODS: We conducted a 20-year register-based follow-up of 150 patients with first-time psychiatric hospitalizations. At baseline, all participants underwent a comprehensive diagnostic assessment. Follow-up data were obtained through linkage to national registers, providing information on psychiatric diagnoses, education, family formation, crime, mortality, and suicide. Cumulative incidence functions accounting for competing risks were calculated stratified on baseline diagnoses. RESULTS: Only seven participants (4.6%) had no further contact with hospital-based psychiatry during the 20-year follow-up. During the follow-up period, 37.9% received a diagnosis of schizophrenia, 35% schizotypy, 14.4% depression, 24.6% personality disorder, 11% bipolar disorder, and 6.1% substance use disorder. Participants with a baseline diagnosis of schizophrenia, schizotypy, or depression had a significantly higher probability of receiving the same diagnosis during follow-up (schizophrenia 81.6%, schizotypy 69.4%, and depression 53.3%), whereas this was not the case for participants with a baseline diagnosis of personality disorder. Mortality was elevated (5.9%), with suicide accounting for one-third of all deaths, ten times the national average. CONCLUSIONS: A first psychiatric hospitalization in early adulthood marked the beginning of a longer clinical trajectory: 95% of participants re-entered hospital-based care or had prolonged initial hospitalization. The findings emphasize the importance of diagnostic assessment and sustained care to improve prognosis and reduce social impairment and premature death.