Study Overview: This research is testing a medicine called lumateperone for kids and teens aged 10 to 17 who have bipolar disorder and are feeling very sad, known as a major depressive episode (MDE). Bipolar disorder is a condition causing extreme mood swings. The study uses a method where neither the participants nor the researchers know who gets the actual medicine and who gets a fake pill, called a placebo, to ensure fairness. The study lasts for about 9 weeks.

• Study Length: The study spans 9 weeks, including screening, treatment, and follow-up phases.
• Visits and Treatment: Participants will visit the clinic several times and will either get the medicine or a placebo.
• Risks and Monitoring: Safety is monitored closely, and a doctor will assess if the participant is safe to join the study.

Eligibility: Kids must have a diagnosis of bipolar disorder, have experienced mood swings before, and their current sad episode should last between 4 weeks and 12 months. They should not have other main mental issues except for ADHD, which must be stable if treated. Kids with recent suicidal behavior or risks are not included for safety reasons.