In Arm 1, patients will begin CBD in period 1 and receive placebo in period 2. In Arm 2, patients will begin placebo in period 1 and receive CBD in period 2. In Arm 3, patients will receive CBD for the entire 27 week study duration without washout. Each study period is 12 weeks and dose will be titrated up for 1 week at the beginning of a treatment period and titrated down for 1 week at the end of a treatment period, with a two week placebo washout between periods for Arms 1 and 2. The titration dose will be 5mg/kg/day and the treatment dose will be 10mg/kg/day.

The Aberrant Behavior Checklist- 2nd Edition (ABC-2) is a standard parent/caregiver reported behavioral outcome measure for use in developmental disability clinical trials. The ABC-2 is a 58-item questionnaire and measures domains of Irritability, Lethargy/Social Withdrawal, Stereotypic Behavior, Hyperactivity/noncompliance, and Inappropriate Speech. Behaviors are assessed using a 4-point Likert scale. Scores range from "not at all a problem" (0) to "the problem is severe in degree" (3). The Stereotypic Behavior subscale range is from 0 to 21.

The Aberrant Behavior Checklist- 2nd Edition (ABC-2) is a standard parent/caregiver reported behavioral outcome measure for use in developmental disability clinical trials. The ABC-2 is a 58-item questionnaire and measures domains of Irritability, Lethargy/Social Withdrawal, Stereotypic Behavior, Hyperactivity/noncompliance, and Inappropriate Speech. Behaviors are assessed using a 4-point Likert scale. Scores range from "not at all a problem" (0) to "the problem is severe in degree" (3). The Inappropriate Speech subscale range is from 0 to 12.

The Aberrant Behavior Checklist- 2nd Edition (ABC-2) is a standard parent/caregiver reported behavioral outcome measure for use in developmental disability clinical trials. The ABC-2 is a 58-item questionnaire and measures domains of Irritability, Lethargy/Social Withdrawal, Stereotypic Behavior, Hyperactivity/noncompliance, and Inappropriate Speech. Behaviors are assessed using a 4-point Likert scale. Scores range from "not at all a problem" (0) to "the problem is severe in degree" (3). The Hyperactivity/Noncompliance subscale range is from 0 to 48.

The Anxiety, Depression, and Mood Scale (ADAMS) is a 28-item parent-report scale designed for individuals with disabilities to measure domains of anxiety (range 0 - 21), depression (range 0 - 21), hyperactivity (range 0 - 15), social avoidance (range 0 - 21), and obsessive/compulsive behavior (range 0 - 9). The total score is the sum of all items (range 0 - 87). Items are rated on a scale of "not a problem" (0) to "severe problem" (3).

The Anxiety, Depression, and Mood Scale (ADAMS) is a 28-item parent-report scale designed for individuals with disabilities to measure domains of anxiety (range 0 - 21), depression (range 0 - 21), hyperactivity (range 0 - 15), social avoidance (range 0 - 21), and obsessive/compulsive behavior (range 0 - 9). The total score is the sum of all items (range 0 - 87). Items are rated on a scale of "not a problem" (0) to "severe problem" (3).

The Anxiety, Depression, and Mood Scale (ADAMS) is a 28-item parent-report scale designed for individuals with disabilities to measure domains of anxiety (range 0 - 21), depression (range 0 - 21), hyperactivity (range 0 - 15), social avoidance (range 0 - 21), and obsessive/compulsive behavior (range 0 - 9). The total score is the sum of all items (range 0 - 87). Items are rated on a scale of "not a problem" (0) to "severe problem" (3).

The Social Responsiveness Scale - 2nd Edition (SRS-2) is a standardized questionnaire that provides T-scores in domains of social communication, social motivation, social cognition, and restrictive/repetitive behaviors. The SRS-2 Total T-score ranges from 30 to ≥90 with higher scores indicating greater deficiencies in reciprocal social behavior.

The Ohio Autism Clinical Impressions Scale - Severity (OACIS-S) is a 10-item, clinician completed measures based upon interview and/or observation. The OACIS-S assesses severity in domains of social interaction, aberrant behavior (including irritability and aggressive behavior), repetitive or ritualistic behavior, verbal communication, nonverbal communication skills, hyperactivity and inattention, anxiety and fearfulness, sensory sensitivities, restricted and narrow interests, and a global rating of autism severity. A 7-point Likert scale is used with scores ranging from "normal" (1) to "among the most severe" (7).

The Ohio Autism Clinical Impressions Scale - Improvement (OACIS-I) is a 10-item, clinician completed measures based upon interview and/or observation. The OACIS-I assesses improvement in domains of social interaction, aberrant behavior (including irritability and aggressive behavior), repetitive or ritualistic behavior, verbal communication, nonverbal communication skills, hyperactivity and inattention, anxiety and fearfulness, sensory sensitivities, restricted and narrow interests, and a global rating of autism severity. A 7-point Likert scale is used with scores ranging from "very much improved" (1) to "very much worse" (7).

The Autism Screening Instrument for Educational Planning - 3rd Edition (ASIEP-3) is a 12-minute play-based assessment that evaluates social interactions and social responses. Videos of the session are coded for interactions, social avoidance, and negative behaviors (self-stimulatory, aggression). The vocal behavior is also coded as a separate domain to provide a sample of language function.

The Repetitive Behavior Scale - Revised (RBS-R) is a caregiver-completed, 43-item questionnaire assessing repetitive behaviors with 6 subscales: stereotyped (range 0 - 27), ritualistic/sameness (range 0 - 36) , self-injurious (range 0 - 24), compulsive (range 0 - 18), and restricted (range 0 - 9). The total score ranges from 0 to 129, with a higher score indicating more significant problems with repetitive behaviors. Repetitive Behaviors are assessed using a 4-point Likert scale. Scores range from "behavior does not occur" (0) to "behavior occurs and is a severe problem" (3).

The Brief Rating Inventory of Executive Functioning - 2nd edition (BRIEF-2) is a standardized rating scale that measures domains of executive functioning, including behavior regulation (inhibition, self-monitoring), emotional regulation (shifting, emotional control), and cognitive regulation (initiation, working memory, plan/organize, task monitoring, and organization of materials). It is made up of 63 items with three answer options (1 = Never; 2= Sometimes; 3=Often). Each item on the parent form is scored 1-3 (1 = Never; 2 = Sometimes; 3 = Often), yielding a raw score of the global scale range from 63 to 189. T scores (M = 50, SD = 10) are used to interpret the level of executive functioning. T-score range is 0-100, and higher scores are indicative of more severe deficiency - 65 or higher is considered to be in the "clinically significant" range.

The Brief Rating Inventory of Executive Functioning - 2nd edition (BRIEF-2) is a standardized rating scale that measures domains of executive functioning, including behavior regulation (inhibition, self-monitoring), emotional regulation (shifting, emotional control), and cognitive regulation (initiation, working memory, plan/organize, task monitoring, and organization of materials). It is made up of 63 items with three answer options (1 = Never; 2= Sometimes; 3=Often). For the ADHD score, 18 items on the BRIEF-2 that correlate with clinical criteria for a diagnosis of ADHD each receive a score from 1-3 (1 = Never; 2 = Sometimes; 3 = Often). These items are summed and produce a range from 18-54, with higher values indicating more ADHD symptoms.

The Brief Rating Inventory of Executive Functioning - 2nd edition (BRIEF-2) is a standardized rating scale that measures domains of executive functioning, including 3 index scores of behavior regulation (inhibition, self-monitoring), emotional regulation (shifting, emotional control), and cognitive regulation (initiation, working memory, plan/organize, task monitoring, and organization of materials). It is made up of 63 items with three answer options (1 = Never; 2= Sometimes; 3=Often). Each item on the parent form is scored 1-3 (1 = Never; 2 = Sometimes; 3 = Often), yielding a raw score of the global scale range from 63 to 189. T scores (M = 50, SD = 10) are used to interpret the level of executive functioning. T-score range is 0-100, and higher scores are indicative of more severe deficiency - 65 or higher is considered to be in the "clinically significant" range.

The Sleep Clinical Global Impressions - Severity Scale (Sleep CGI-S) is a clinician completed measure based upon interview which assesses severity in domains of ability to fall asleep and remain sleeping independently, bedtime resistance; sleep onset delay; night awakening; caregiver satisfaction with their child's current sleep patterns; family functioning, as affected by their child's current sleep patterns. A 7-point Likert scale is used for each domain with scores ranging from "no concerns"/"does not occur" (1) to "Among the worst" (7).

The Sleep Clinical Global Impressions - Improvement Scale (Sleep CGI-I) is a clinician completed measure based upon interview which assesses improvement in domains of ability to fall asleep and remain sleeping independently, bedtime resistance; sleep onset delay; night awakening; caregiver satisfaction with their child's current sleep patterns; family functioning, as affected by their child's current sleep patterns. A 7-point Likert scale is used for each domain with scores ranging from "very much improved" (1) to "very much worse" (7).

The Autism Family Experience Questionnaire (AFEQ) is a 48-item questionnaire that measures family quality of life with domains of experience of being a parent (range 13 - 65), family live (range 9 - 45), child development and social relationships (range 14 - 70), and child's feelings and behavior (range 12 - 60). The sum of all domains gives the total score (range 48 - 240). Each question is assessed using a 5-point Likert scale. Scores range from "always" (1) to "never" (5)". For the total score and the domain scores a higher score indicates a lower outcome.

National Institutes of Health Patient Reported Outcome Measures Information System (NIH PROMIS) will be used to quantify psychological wellbeing and quality of life through self-report and/or parent proxy report. Satisfaction with Social Roles and Activities - Short Form 4a assesses satisfaction with performing one's usual social roles and activities and uses a 5-point Likert scale with scores ranging from "not at all" (1) to "very much" (5). The sum of all scores yields a total raw score (range 4 - 20) with higher scores indicating a greater level of satisfaction. The final score is represented by the T-score, a standardized score with a mean of 50 and a standard deviation (SD) of 10.

National Institutes of Health Patient Reported Outcome Measures Information System (NIH PROMIS) will be used to quantify psychological wellbeing and quality of life through self-report and/or parent proxy report. Life Satisfaction - Short Form 8b assesses an individual's cognitive evaluation of life experiences and whether one likes his/her life or not. Each question is scored using a 5-point Likert scale with scores ranging from "not at all" (1) to "very much" (5). The sum of all scores yields a total raw score (range 8 - 40) with higher scores indicating a greater level of satisfaction. The final score is represented by the T-score, a standardized score with a mean of 50 and a standard deviation (SD) of 10.

National Institutes of Health Patient Reported Outcome Measures Information System (NIH PROMIS) will be used to quantify psychological wellbeing and quality of life through self-report and/or parent proxy report. Positive Affect - Short Form 41 assesses momentary positive or rewarding affective experiences, such as feelings and mood associated with pleasure, joy, happiness, and excitement. Each question is scored using a 5-point Likert scale with scores ranging from "not at all" (1) to "very much" (5). The sum of all scores yields a total raw score (range 4 - 20) with higher scores indicating a greater level of positive affect. The final score is represented by the T-score, a standardized score with a mean of 50 and a standard deviation (SD) of 10.

The Pediatric Quality of Life Inventory (PedsQL) - Core Scale is a 23-item caregiver questionnaire to evaluate overall quality of life (QOL) in domains of physical functioning, emotional functioning, social functioning, and school functioning. A 5-point Likert scale is used with responses ranging from "Never" (0) to "Almost Always" (4). Items are reversed scored and transformed to a 0 - 100 scale as follows: 0=100, 1=75, 2=50, 3=25, and 4=0. The total score is the sum of all the items over the number of items answered with higher scores indicating better health-related quality of life (HRQoL).

The Pediatric Quality of Life Inventory (PedsQL) - Cognitive Scale is a 6-item caregiver questionnaire to evaluate an individual's mental abilities including learning, thinking, remembering and attention . A 5-point Likert scale is used with responses ranging from "Never" (0) to "Almost Always" (4). Items are reversed scored and transformed to a 0 - 100 scale as follows: 0=100, 1=75, 2=50, 3=25, and 4=0. The total score is the sum of all the items over the number of items answered with higher scores indicating lower problems.

The Autism Screening Instrument for Educational Planning - 3rd Edition (ASIEP-3) is a 12-minute play-based assessment that evaluates social interactions and social responses. Videos of the session are coded for interactions, social avoidance, and negative behaviors (self-stimulatory, aggression). The vocal behavior is also coded as a separate domain to provide a sample of language function.

The Parent/Caregiver Improvement Scale is caregiver-completed questionnaire that assesses improvement in domains of communication skills, social skills, daily living skills and overall behavioral symptoms. A 7-point Likert scale is used for each domain with scores ranging from "very much improved" (1) to "very much worse" (7).