Transcranial Photobiomodulation for Reducing Autism Symptoms in Children

Inclusion Criteria: 1. Male or female participants between 2 years and 6 years of age (inclusive), of all races. 2. Previously diagnosed with moderate or severe ASD by a licensed professional. 3. Participants may be receiving any behavioral intervention therapy (e.g., ABA, Floor Time) during the course of the treatment. The final statistical analysis will control for the participants receiving behavioral therapies in control and experimental conditions. We expect the majority of the participants in both control and experimental conditions to be receiving behavioral therapies. There is no known interactions or complications of tPBM with behavioral therapy. 4. Parents of participants must understand the nature of the study. 5. Parents of participants must sign an IRB- approved informed consent form before initiation of any study procedures. 6. Parents of participants must have a level of understanding sufficient to communicate with the investigator and study coordinator, and to cooperate with all tests and examinations required by the protocol. 7. Participant child experiencing a major psychiatric disorder will be allowed to participate in the study provided they do not meet any exclusionary criteria. 8. The participant child is willing to participate in this study. Exclusion Criteria: 1. Participant child is experiencing severe self-injurious behavior or severe aggressive behavior to self or others (within past 7 days). 2. Participant has been diagnosed with another psychiatric or neurological disorder (e.g. epilepsy) or have exhibited symptoms of major psychiatric disorders within the last 30 days. 3. Participant has an unstable medical condition (that requires clinical attention). 4. Participant has a significant skin condition at the procedure sites (i.e., hemangioma, scleroderma, psoriasis, rash, open wound or tattoo). 5. Participant has an implant of any kind in the head (e.g. stent, clipped aneurysm, embolised AVM, implantable shunt - Hakim valve). 6. Participant has receiving medication on a regular basis for Autism or any other medical condition. 7. Any use of light-activated drugs (photodynamic therapy) within 14 days prior to study enrollment (in US: Visudine (verteporfin) - for age related macular degeneration; Aminolevulinic Acid- for actinic keratoses; Photofrin (porfimer sodium) - for esophageal cancer, non-small cell lung cancer; Levulan Kerastick (aminolevulinic acid HCl) - for actinic keratosis; 5-aminolevulinic acid (ALA)- for non-melanoma skin cancer). 8. Current treatment with a psychotropic medication. 9. Investigator and his/her immediate family, defined as the investigator's child or grandchild.