Psychiatric disorders among survivors of childhood acute lymphoblastic leukemia in Denmark and Sweden

Background
The diagnosis and treatment of childhood acute lymphoblastic leukemia (ALL) may impact mental health. We investigated the long-term risk of psychiatric disorders among survivors of ALL in a population-based cohort study.

Methods
We identified patients diagnosed with ALL in Denmark and Sweden before age 20 during 1982–2008. Survivors of ALL (n = 2026), their siblings (n = 3027), and population comparison subjects (n = 9713) were followed for hospital contacts for psychiatric disorders from 5 years after ALL diagnosis (or corresponding index date) until 2017.

Results
By age 30, the absolute risk of psychiatric hospital contacts was 19.9% (95% confidence interval [CI]: 17.9–22.1) for ALL survivors, 18.5% (95% CI: 16.9–20.2) for siblings, and 18.3% (95% CI: 17.3–19.2) for population comparison subjects. Overall, survivors were at higher risk of any psychiatric disorders than siblings (hazard ratio [HR] = 1.25; 95% CI: 1.04–1.50), and population comparison subjects (HR = 1.20; 95% CI: 1.06–1.35). The subgroup of survivors (n = 332) who received a hematopoietic stem cell transplantation (HSCT) and/or had a relapse were at highest risk of psychiatric disorders (HR = 2.07; 95% CI: 1.26–3.41 compared to siblings; HR = 1.67; 95% CI: 1.25–2.23 compared to population comparison subjects).

Conclusions
The overall absolute risk of psychiatric hospital contacts among ALL survivors was close to that in siblings and population comparison subjects. The modestly increased relative risk was mainly driven by the subgroup of survivors who received HSCT and/or had a relapse. Our findings are reassuring for the large subgroup of ALL survivors without HSCT or relapse, and provide novel insight on both absolute and relative risk of hospital contacts for psychiatric disorders.