Cannabis use the week before admission to psychiatric in-patient service as a marker of severity

Objective: To evaluate if cannabis dose recorded as standard joint unit (SJU) consumed before admission and other related factors have an influence on psychiatric inpatient's symptom severity and clinical outcomes. Methods: Cross-sectional study in an acute psychiatric inpatient unit including 106 individuals. Quantity of cannabis was measured as SJU and symptoms severity through the Brief Psychiatric Rating Scale (BPRS). Secondary outcomes (e.g. length of stay) were also assessed. Bivariate analyses and multivariate analyses were performed to determine the effect of SJU consumed before admission on measures of clinical severity. Results: Point prevalence of cannabis use before admission was 25.5%. Mean BPRS score was 55.8 (SD = 16.1); and 62.9 (SD = 11.1) among cannabis users. A low degree positive correlation between SJU consumed the week before admission and BPRS score (r(s) = 0.28, p = 0.03) was found. In the multivariate analyses both main diagnostic group, Schizophrenia and other psychotic disorders vs. others (Bipolar and Unipolar Affective Disorders and Addictive disorders) (B = 8.327; 95% CI 4.976-11.677) and need of PRN ("pre re nata" or when necessary) administration of antipsychotics and benzodiazepines (B = 12.13; 95% CI 6.868-17.393) were significant predictors, both increasing BPRS score. Conclusions: The study did not find a correlation between SJU consumed last week and psychiatric severity. On the other hand, individuals with psychotic disorders reported a higher prevalence of cannabis use the week before admission and displayed higher BPRS scores, which points to the need for the development of tailored interventions for high-risk groups. The SJU is a useful quantification tool suitable for further clinical research.