Trazodone's FDA prescribing information states that safety and effectiveness in the pediatric population have not been established. Any use in children or teenagers would be an off-label decision, typically made by a specialist (such as a child psychiatrist) after careful consideration of alternatives.
The antidepressant-class boxed warning about increased suicidal thoughts and behaviors specifically applies to patients under 25, making careful monitoring especially important in any pediatric or young-adult use.