What was the cause of Marilyn Monroes suicide?

The cause of Marilyn Monroe's death was a drug overdose, specifically barbiturates. Monroe had a long history of struggling with substance abuse, including prescription medication dependency. The overdose was ruled as a probable suicide, as she was found dead in her home with high levels of barbiturates in her system and had previously expressed thoughts of suicide. The combination of mental health issues, personal struggles, and dependence on drugs ultimately led to her tragic and untimely death.