The cause of death for ex-NBA player Darius Morris has just been revealed … heart disease is the killer, with drug and alcohol use playing a big role.

Darius’ official cause of death is coronary artery disease … according to the Los Angeles County Medical Examiner.

According to the ME’s death investigation summary, obtained by TMZ Sports, drug and alcohol use was a significant factor in Darius’ death … specifically, the effects of cocaine, hydrocodone and ethanol.

The former Los Angeles Lakers guard’s death is being ruled accidental.

As we reported … Darius’ was found dead in a Los Angeles-area home on May 2 … the ME report says he was examined the following day and he still had alcohol, cocaine and hydrocodone in his system.

The ME report adds … there were no drugs found at the scene and Darius’ body was decomposing when he was found … with a foul odor coming from his corpse. He was last known to be alive April 22, when his mom says he told her he was feeling ill and experiencing flu-like symptoms.

Darius, who played 4 seasons in the NBA with the Lakers, 76ers, Clippers, Grizzlies and Nets before going overseas, was only 33 years old.

RIP.