Longitudinal outcomes in pediatric- and adult-onset bipolar patients compared to healthy and schizophrenia controls

Objectives: Comparing outcomes of bipolar disorder (BD) with schizophrenia (SCZ) and psychiatrically healthy controls (PHC), contrasting pediatric-onset with adult-onset disorders. Methods: A nationwide cohort study, including patients with an incident diagnosis of BD or SCZ registered in the Danish National Patient Registry and corresponding PHCs. Outcomes were (a) duration of hospitalization, (b) psychiatric admissions, (c) psychiatric outpatient contacts, (d) bone-fracture-related healthcare contacts, (e) self-harm-related healthcare contacts (including suicide and non-suicidal self-injuries), and (f) criminal charges. Incidence rate ratios (IRRs), adjusted for age at first psychiatric contact, substance abuse and parental psychiatric illness, were calculated, comparing pediatric-onset BD (5-17 years) and adult-onset BD (18-39 years) with age- and sex-matched SCZ patients and PHC. Results: Pediatric-onset BD (n = 349) performed better than 1:1-matched pediatric-onset SCZ (n = 349) on all six outcomes (IRR = 0.30 for self-harm-related contacts (P < 0.001) to IRR = 0.86 for criminal charges (P = 0.05). Similar, but less pronounced results were observed comparing 1:1-matched adult-onset BD (n = 5515) with adult-onset SCZ (n = 5515) IRR = 0.58 for psychiatric outpatient contact (P < 0.001) to IRR = 0.93 for criminal charges (P < 0.001), except for more bone-fracture-related contacts in adult-onset BD (IRR = 1.13, P < 0.01). Comparing pediatric-onset BD (n = 365) to 1:3-matched PHC (n = 1095), only self-harm-related contacts differed significantly (IRR = 2.80, P < 0.001). Conversely, comparing adult-onset BD (n = 6005) with 1:3-matched PHC (n = 18 015), self-harm-related contacts (IRR = 16.68, P < 0.001), bone fractures (IRR = 1.74, P < 0.001), and criminal charges (IRR = 2.03, P < 0.001) were more common in BD. Conclusion: BD was associated with poorer outcomes than PHC, but better outcomes than SCZ. Furthermore, outcomes were more favorable in pediatric-onset BD when indirectly contrasted to adult-onset BD.