What is the evidence that hydroxyurea improves health-related quality of life in patients with sickle cell disease?

A 10-year-old male patient with homozygous sickle cell disease presents for a follow-up clinic visit after a recent hospitalization for a painful vasoocclusive event. His parents mention that in the past year he has had 4 hospitalizations for vasoocclusive events, 2 of which were complicated by the development of acute chest syndrome that resulted in transfer to the intensive care unit. He has missed many school days and may be retained a grade this year. He feels particularly sad about missing the school field trip that occurred during his last hospitalization. He also reports that he is not able to keep up with his friends when participating in physical activities at school. The child's parents are worried that he may be depressed. You as the provider discuss the option of hydroxyurea therapy. His parents ask if hydroxyurea would improve his overall well-being and functioning.