Type 1 diabetes (T1D) is known to have adverse long-term health and social outcomes, but the modifying factors are largely unknown. We investigate to what extent T1D outcomes are modified by area-, household-, and individual-level social and economic characteristics in Finland. National registers from 1987 to 2020 were used to identify all 3,048 children with T1D diagnosed at age seven to 17 and matched controls (n=78,883). Using causal forests, we estimated the average association between T1D and adult health, social, and economic outcomes at ages 28-30, and the modifying roles of more than 30 covariates. Individuals with T1D were more likely to be deceased (2.3% vs. 0.9% in the control group), to use antidepressants (17% vs. 13%), and to be unpartnered (36% vs. 32%), and had more months of unemployment (1.18 vs. 1.02) and lower annual income (25,697 euros vs. 27,453 euros), but not significantly lower educational attainment (10.8% vs. 10.3% with only basic education). T1D had a heterogenous association with all outcomes except mortality and income, but no specific population subgroup was vulnerable across all outcomes. However, women with T1D had particularly high rates of antidepressant use, and individuals from low socioeconomic families were more likely to be unpartnered.