Setting: A double blind randomized placebo-controlled trial with crossover. Methods: One hundred and twenty participants ages 6-30 years, with established ASD diagnosis and moderate to severe refractory behavioral problems will be treated with placebo and cannabinoids mix in a randomized cross-over trial. Each intervention period will be 12 weeks with additional 4 weeks for gradual dose decrease and wash-out. Baseline evaluations will include: Autism diagnostic observation schedule (ADOS-2), Social Communication Questionnaire (SCQ), Vineland II (interview based), Childhood Autism Rating Scale (CARS-2, observation based). Primary outcome measures: Home Situations Questionnaire-Autism Spectrum Disorder (HSQ-ASD), Child Behavior Checklist (CBCL, parent-rated), and Autism Parenting Stress Index (APSI) will be assessed every 4 weeks. Secondary outcome measures: Clinical Global Impression (CGI, improvement and efficacy index items, clinician-rated) and Social Responsiveness Scale (SRS, parent and teacher rated) will be assessed at baseline and termination of each treatment period. Adverse events will be taped every 4 weeks.