The use of cannabis as a viable treatment for patients suffering from chronic, painful conditions is a controversial topic. Many studies are being conducted to test its effects on pain, but the risks must be examined as well.

A recent study by Di Forti, et al., is an examination of the relationship between cannabis use and psychosis. Specifically, the study looked at cannabis with higher potency and the onset of psychosis.

The average potency of cannabis has increased significantly in recent years. Between 1980 and 2008, the average percentage of delta-9 tetrahydrocannabinol in cannabis seized by law enforcement has increased from 2 percent to 8.5 percent.

The study involved 280 participants aged 18 to 65 from in-patient mental hospitals in London who were admitted initially for psychosis. There was also an enrollment of 174 participants to establish a control group. The control group participants were recruited through advertisements in newspapers, on the Internet and recruitment at businesses.

The participants provided information about socioeconomic factors and drug use history and those having experience using cannabis completed the Cannabis Experience Questionnaire. Logistic regression analysis was employed to examine the relationship between cannabis use and psychosis admissions.

57 percent of hospital admissions and 63 percent of control group participants reported using cannabis at least once. Of those having used cannabis, 77 percent of hospital admissions and 33 percent of the control group used cannabis daily.

The researchers also looked specifically at the potency of the cannabis used and the length of time it was used. 78 percent of hospital cases preferred high-potency, or “skunk” cannabis, compared with 37 percent of controls. 59 percent of the hospital cases reported using cannabis for more than five years, compared with 38 percent of the control group.

There are several limitations to this study. The study relied on self-report for drug use history, including the potency and type of cannabis used and the length of time the cannabis was used. Also, the researchers collected information about the participants’ use of other drugs, but did not include it in the study, which may also have an impact on psychosis.

The findings of this study show that patients admitted for psychosis were significantly more likely to have used high-potency cannabis than their control group counterparts. Additional research is needed to evaluate the possible effects of other types of substance abuse on psychosis, since cannabis is often used in conjunction with other drugs.

Researchers will also want to establish a link between different temporal relationships with cannabis and psychosis to determine if length of time used impacts the onset of psychosis.