Trial of Diphenhydramine for Sleep in Children With Autism

This study tests whether diphenhydramine (commonly known as Benadryl) can help improve sleep in children and teenagers with autism spectrum disorder (ASD) who also have sleep problems. You may be eligible if: - Your child is between 8 and 17 years old - Your child has an ASD diagnosis confirmed by standard assessments - Your child has sleep problems (CSHQ score of 41 or higher) - Medications have been stable for at least 2 weeks (or 4 weeks for Prozac) - You are able to bring your child to all clinic visits reliably You may NOT be eligible if: - Your child has active suicidal thoughts or a diagnosis of schizophrenia or psychosis - Your child has asthma, migraines, active seizures, or significant liver, kidney, or heart problems - Your child is pregnant or sexually active without reliable contraception - Your child is taking benzodiazepines, antiepileptic medications for seizures, melatonin, or antihistamines - Your child has a history of allergy or severe side effects from diphenhydramine - Your child is taking anticholinergic medications Talk to your doctor to see if this trial is right for you.