A Study to Investigate Behavioral and Other Co-Occurring Outcomes With Epidiolex as Add-On Therapy in Participants Aged 1 to 65 Years of Age With Tuberous Sclerosis Complex

Inclusion Criteria: 1. Is within the required age range at the time of signing (or at the time of the participant's parent(s)/Legally Authorized Representative (LAR) signing) the informed consent or providing assent (as applicable): * Participants based in the US: 1 to 65 years of age, inclusive. * Participants based outside the US: 2 to 65 years of age, inclusive. 2. Has a confirmed clinical diagnosis of TSC with a history of seizures in accordance with the 2012 International Tuberous Sclerosis Complex Consensus Conference criteria. 3. Has behaviors (eg, aggression, impulsivity, temper tantrum, self-injury, hyperactivity, extreme shyness, mood swings, poor eye contact, repetitive behaviors, restlessness, difficulty getting along with peers, rigid/inflexible to procedure and/or change) that are considered moderate or severe per the CareGI-S at Screening. 4. Is taking 1 or more anti-seizure medicine (ASM) at a dose that has been stable for at least 4 weeks prior to Screening. • All medications or interventions for epilepsy (including ketogenic diet and any neurostimulation devices for epilepsy) must have been stable for 4 weeks prior to screening and any major changes to treatment regimens should be discussed with the medical monitor. 5. Is naïve to CBD-OS treatment or has been off CBD-OS treatment for at least 3 months prior to Screening. 6. Is willing to maintain any factors expected to affect seizures stable (eg, alcohol consumption, smoking, concomitant medication usage). 7. Is male or female 1. Male participants: • Male participants are eligible to participate if they agree to the following during the intervention period and for at least 2 weeks, corresponding to the time needed to eliminate the study intervention after the last dose of study intervention: * Refrain from donating fresh unwashed semen. PLUS * Use a male condom in addition to a second method of acceptable contraception used by their female partners when having sexual intercourse with a women of childbearing potential (WOCBP) who is not currently pregnant. 2. Female participants: * A female participant is eligible to participate if she is not pregnant or breastfeeding and one of the following conditions applies: * Is a woman of nonchildbearing potential. OR * Is a WOCBP and using a contraceptive method that is highly effective, preferably with low user dependency during the study intervention period and for at least 3 months after the last dose of study intervention. The investigator should evaluate the potential for contraceptive method failure (eg, noncompliance, recently initiated) in relationship to the first dose of study intervention. * A WOCBP must have a negative highly sensitive pregnancy test within 28 days before the first dose of study intervention. Exclusion Criteria: 1. Has a clinically significant unstable medical condition other than epilepsy. 2. Has an illness during the 4 weeks prior to screening other than epilepsy which, in the investigator's opinion, could affect study outcomes. 3. Has TSC-specific tumor growth which, in the investigator's opinion, could affect the effectiveness endpoints. 4. Has previously undergone significant surgery for epilepsy that, in the investigator's opinion, may impact the assessment of outcomes. 5. Has initiated felbamate within the last 12 months prior to Screening. 6. Is currently using or has in the past used recreational or medicinal cannabis or synthetic cannabinoid-based medications within the 3 months prior to Screening and is not willing to undergo a 1-month washout period before being rescreened. 7. Has received an investigational medicinal product within the 3 months prior to the Screening Visit. 8. Has previously been assigned study intervention for this study or is currently enrolled in any other interventional study. 9. Has laboratory values at the Baseline Visit that are abnormal and of clinical significance in the investigator's opinion. 10. Participant has significantly impaired hepatic function at the Baseline Visit. 11. Has any history of suicidal behavior or any suicidal ideation of type 4 or 5 as evaluated with C-SSRS or Children's C-SSRS at the Screening Visit (for participants ≥ 4 years of age). 12. Has any known or suspected hypersensitivity to cannabinoids or any of the excipients of CBD-OS. 13. Has a known or suspected history of alcohol or substance abuse.