Cannabis abuse in FEP patients predicts poor symptom control

By Ingrid Grasmo, medwireNews Reporter

Patients with first-episode psychosis (FEP) and comorbid cannabis abuse are at high risk for poor symptom control even when on medication, suggest findings published in Schizophrenia Research.

Notably, patients who continued their marijuana use were twice as likely to remain compliant with their medication compared with those who stopped taking cannabis after entering treatment. The authors speculate that patients tend to make a decision either to stop using cannabis and not take medications or to continue using cannabis and then become increasingly adherent to medications.

"These results point to the importance of working with patients to reduce cannabis consumption, which seems to adversely affect psychotic symptomatology even in the context of intensive pharmacologic and psychosocial treatment for a first episode of psychosis," say Ashok Malla (McGill University, Montreal, Quebec, Canada) and co-authors.

To examine the variation in medication adherence associated with cessation or continuation of cannabis use and the possible interaction of these factors with symptom levels and outcome, the researchers followed up 48 FEP patients who met DSM-IV criteria for a currently active cannabis abuse disorder over a 12-month period.

Just over half (58.3%) of patients retained an active cannabis use disorder at the end of follow up, suggesting that a substantial proportion of patients with co-morbid FEP are able to substantially reduce or stop their marijuana use even in the absence of a specific treatment module addressing substance use.

Patients who either continued or ceased to use cannabis throughout the first year became less adherent to medication during the first 6 months in treatment.

However, patients who continued to use cannabis showed incrementally higher levels of medication adherence by month 12 compared with those who stopped using cannabis (92 vs 40%) - a finding deemed "surprising" by the researchers.

"This result is suggestive that the cannabis abusing FEP patients are making two crucial decisions during treatment - whether to reduce or cease consumption of cannabis, and whether or not to continue to take medications," comment the authors.

No overall effect of continued cannabis use on symptom levels was observed at 12 months, but after controlling for medication adherence patients with continuous cannabis used showed significantly more psychotic symptomatology.

This finding is of particular importance, given the high levels of medication adherence in patients who continued to use cannabis throughout the study period.

The researchers note that further research is needed to identify which type of intervention service is best for individual patients, as the interaction between psychotic symptoms, cannabis use, and antipsychotic medication is likely to play a very significant role.

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