The purpose of this study is to find out how the brain of people with autism is affected by Propranolol. Propranolol is not FDA approved for the treatment of autism. Propranolol is FDA approved for the treatment of heart conditions such as blood pressure

This research is being done because there are currently no drug treatment options for language impairments and social difficulties often experienced by people with autism.

The specific aim of this study is to examine the effects of serial doses of propranolol on social interaction, and secondarily on language tasks, anxiety, adaptive behaviors, and global function in high functioning adults and adolescents with autism in a double-blinded, placebo-controlled trial. The investigators will also examine whether response to treatment can be predicted based upon markers of autonomic functioning, such as skin conductance, heart rate variability (HRV), and the pupillary light reflex (PLR), and whether anxiety can predict treatment response. The hypothesis is that social functioning and language abilities will benefit from serial doses of propranolol, and that those with the greatest degree of autonomic dysregulation, or the lowest functional connectivity, will demonstrate the greatest benefit from the drug.

Inclusion Criteria:

• Autism Spectrum Disorder diagnosis
• intelligence quotient (IQ) >= 85 (if aged 15-24), >= 75 (if aged 7-14)
• Native English speaker
• Parent or caregiver must older than 18 years and be a native English speaker

Exclusion Criteria:

• Taking Alpha 2 agonists
• Non-autism learning disorder
• Other major psychiatric disorders
• Other neurological disorders
• Major head trauma
• Reaction to adhesives
• Diabetes
• Reactive airway disease
• Thyroid disease
• Bradyarrhythmias
• Unexplained syncope
• Pregnancy
• Possible interacting drugs
• Underweight (<20kg if aged 7-14 years)
• Factors affecting ability to have an MRI (if aged 15-24 years)