What could be a cause of bedwetting at 16 years old?

See his /her doctor: Has he wet the bed his entire life or is this a return of wetting after having had a pattern of dry nights? Either problem's best addressed by his doctor. Until the visit, make sure he's not constipated as this can exacerbate the problem. Bedwetting often familial and worse with deep sleepers. If the problem has been there always it's unlikely to have a medical cause. New onset more concerning.

Production, storage: Bedwetting from birth could be immature nervous system control, small functional bladder capacity or xs urine production at night all usually respond to treatment with wetting alarm or medication. Secondary onset wetting could be due to kidney disease or an anatomical abnormality. At age 16 worth seeing a dr. With interest in bedwetting.