Trends in drug use of Scottish drivers arrested under Section 4 of the Road Traffic Act--a 10 year review.

A study of Section 4 RTOA cases submitted to the SPSA forensic science laboratory in Edinburgh over a 12 year period was carried out. The main aims of the study were to identify the most frequently encountered drugs and to determine if there were any major drugs trends from the data collected. Three groups of cases from 1996 to 2000 (102 cases), 2003 (26 cases) and 2008 (295 cases) were examined. The large increase in submissions was mainly due to the introduction of SPSA, whereby the laboratory began to carry out the analysis for all criminal and RTOA cases in Scotland. The preliminary results for the 8 drug groups (amphetamine and related compounds, benzodiazepines, cannabinoids, cocaine, methadone, methylamphetamine and related compounds, morphine and opiates) identified a number of major trends: cannabinoids were consistently present in 40-50% of cases; benzodiazepines more than doubled in frequency to over 80%; there has been a significant increase in cases positive for morphine and methadone--up from less than 2% each to 31% and 23% respectively; there has been an increase in the number of cases screening positive for opiates (19% to 29%); and the frequency of positive cases for cocaine, amphetamine and methylamphetamine remained unchanged (approximately 22%, 6% and 5% respectively). A significant finding was the huge increase in polydrug use. The number of cases positive for 4 or more drug groups has increased from 4% in 1996-2000 to 25% in 2008. In comparison, in the 1996-2000 group 72% of cases were only positive for one drug group compared to 17% in 2008. For those cases which were negative for all 8 drug groups, a screen for potentially impairing prescription and over the counter medicines was carried out. The most frequently encountered medicines were sedatives, sedative antidepressants, sedative antihistamines and antiemetics. These were often found in conjunction with alcohol below the legal limit for driving.