It is widely described in literature, the high comorbidity between drug misuse and psychiatric disorders. 85% of patients with serious mental disorders, use alcohol or tobacco and other drugs. In almost 50% of them consume alcohol and cannabis. If we consider just hospitalized patients, the prevalence varies between 12 and 50% of the cases.That is why in 2003 a multidisciplinary group was formed in order to study drug consumption at hospital and to establish a drug screening protocol to control this issue.The objective of the study is to explain the protocol introduced in 2003 and an example of its benefits specially in the reduction of cannabis consumption.

There was elected a multidisciplnary group formed by the hospital administrator, the laboratory technician, different psychiatrists and nurses. They designed the drug screening protocol that we show in this work.

As an example of the effectiveness of the protocol, we consider the evolution of cannabis misuse before and after protocol enforcement, looking for positive results in urine samples. In 2003, there were taken 2575 urine samples for cannabis screening and in the 35,22% of the cases the result was positive. On the other hand in 2009, 3656 urine samples were collected and just the 17.7% of the determinations were positive.

The design of a specific, serious, standarized drug screening protocol in a hospital permits to control and minimize drug misuse during inpatients' hospitalization.