Drug dependence epidemiology in palliative care medicinal cannabis trials

Drug dependence is becoming increasingly common and meeting palliative care patients with substance use disorders is inevitable. However, data on substance use in these patients are lacking. This study aims to evaluate the prevalence of drug dependence in palliative care patients with advanced cancer and correlate with symptom distress and opioid use.

Palliative care patients with advanced cancer interested in participation in a medicinal cannabis trial were required to complete Alcohol, Smoking and Substance Involvement Screening Test (ASSIST), Edmonton Symptom Assessment Scale (ESAS) and record of concomitant medications including baseline opioid use as part of the eligibility screen.

Of the 182 participants, 167 (92%) reported lifetime alcohol and 132/182 (73%) lifetime tobacco use. No participant reached the threshold criteria for high risk of drug dependence with majority being low risk. There was no correlation between ASSIST score, ESAS and oral morphine equivalent.

This study identified alcohol and tobacco as the main substances used in this group of patients and that most were of very low risk for drug dependence. This suggests routine drug screening for palliative care patient may not be justified, but the high possibility of questionnaire bias is acknowledged.