Substance-induced psychotic disorder refers to abnormal behaviour caused by taking drugs, said Dr Thomas Lee, a psychiatrist at the Resilienz Clinic.

He said: "It refers to the way a person talks or acts. A person could hear voices, hallucinate, or have untrue beliefs such as feeling that everybody is plotting against him.

"Such paranoia is commonly seen in people who have taken street drugs."

These include methamphetamine, also known as Ice, cocaine or LSD. The state of intoxication could last quite some time.

Psychiatrist in private practice, Dr Lim Boon Leng, told The New Paper that there are several ways that a psychotic state can be induced.

Certain drugs, such as LSD, can cause hallucinations almost immediately, even if the abuser does not overdose on it.

He said the most common form of drug-induced psychosis are from substances such as cannabis, which can continue to have effects on the human body for up to six months - long after the drug has left the body.

Chua has a history of poly-substance abuse, which means he used multiple illicit drugs at the same time.

Dr Lee said this would amplify the effects of the drugs.

"The body would be in chaos. Mixing a downer with something that gets you high could lead to unstable, unpredictable effects."

- Clement Yap