One in four new cases of psychotic disorders could be directly linked to the use of high-potency “skunk-like” cannabis, a new study has found.

Researchers from King’s College London found smokers of super-strength cannabis, colloquially known as skunk, were three times as likely to develop symptoms of a psychosis than those who don’t use the drug, the BBC reports.

That risk increases to five times as high if the user smokes skunk on a daily basis.

“The results show that psychosis risk in cannabis users depends on both the frequency of use and cannabis potency,” said Dr. Marta Di Forti, lead author of the study.

However, the team found that milder varieties of cannabis such as hashish did not increase the risk of psychotic illness.

Psychosis refers to hallucinations or delusions that can be found in certain psychiatric conditions such as schizophrenia or bipolar disorder.

Read next: Driving While Stoned Is Much Safer Than Driving Drunk, Says a New Study

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Write to Helen Regan at helen.regan@timeasia.com.