Patterns of Detecting Substances of Abuse in a Large Series of Patients in Spain During 2021-2025

This study was conducted to assess, for the first time, patterns in common drugs of abuse detected in urine samples from a large series of patients treated at a tertiary university hospital and the role of age and sex in these patterns.

This study included samples from all patients analyzed at the Dr. Negrín University Hospital Laboratory from January 2021 to December 2025 with positive immunoassay test results for at least one of the following substances of abuse: cannabis, cocaine, amphetamine/methamphetamine, or opioids. The samples were anonymized, and only the patient's sex and date of birth were included in the analysis.

In total, there were 5019 positive results for at least one of the substances screened (cannabis, opioids, amphetamine, or cocaine). Women represented only 28.2% of all patients with a positive test (p < 0.0001). Substance positivity was strongly influenced by age. Cannabis positivity was observed in 2989 cases (59.9%) and was very high in the younger age groups, consistently declining towards age 65 (94% for <18 years vs. 16.2% for >65 years) (p < 0.0001). In contrast, amphetamine (15.9%) and opioid (13.9%) use rose consistently from 7.5% and 0.7%, respectively, among patients aged <18 years, to 61.3% and 23.1%, respectively, in the >65 age group (p < 0.0001). Cocaine positivity (45.6%) was very low at early ages (5.4% for <18 years group), increased in middle age (62%: 36-55 years group), and decreased in older age (11.9% for >65 years group) (p < 0.0001).

With more than five thousand samples analyzed, our study sheds light on the profile of substance abuse in a large population of patients attending a university hospital. Our results can help to better adjust preventive political actions and medical care, in the context of substance abuse.