Dr Jason Round

Trait impulsivity has been implicated in the misuse of several substances of abuse. In the UK cannabis is primarily smoked in a joint with tobacco. Whilst previous research suggests that cannabis smokers are more impulsive than non-smokers, it remains unclear whether elevated impulsiveness in cannabis smokers may be attributed to the use of tobacco in joints. To date, limited research has attempted to disentangle the effects of cannabis smoking from tobacco smoking, in particular the role trait impulsivity has in the maintenance of addiction to these substances. In this talk I will present evidence from my PhD research, which shows that: (1) distinct dimensions of trait impulsivity are elevated in different drug user groups compared to non-smokers, and (2) differential relationships between trait impulsivity, drug use and dependence exist across different drug users.

BACKGROUND: Cannabis smoking and cigarette smoking often co-occur, yet limited research has investigated the potentially different role impulsivity may play when these behaviours occur in isolation, compared with in combination. AIMS: This study examined trait and behavioural impulsivity as a function of both cigarette and cannabis smoking. METHODS: Trait impulsivity (BIS-11) was compared between 44 non-smokers, 76 cigarette only, 47 cannabis only and 58 cannabis plus cigarette smokers. The effects of cigarette and cannabis smoking on behavioural impulsivity (stop-signal and information sampling tasks) were then assessed in 87 of these participants during a laboratory session. RESULTS: Trait impulsivity was significantly higher in cigarette smokers than non-smokers, irrespective of cannabis use, except for motor impulsivity, where cigarette smoking was only associated with elevated trait impulsivity in non-smokers of cannabis. Dimensions of trait impulsivity were significantly positively related to cigarette smoking frequency and nicotine dependence, but not to cannabis smoking frequency or dependence. Smoking cigarettes or cannabis was associated with significantly impaired reflection impulsivity relative to not smoking either substance. However, no additional increases in reflection impulsivity were observed in those who smoked both cigarettes and cannabis. No group differences in response inhibition were detected. CONCLUSIONS: Heightened trait impulsivity appears to be uniquely related to cigarette smoking, whilst the smoking of cigarettes or cannabis is associated with impairments in reflection impulsivity. Improved outcomes for treating cannabis dependence may result from encouraging concomitant cigarette smokers to cease using both drugs simultaneously in order to reduce heightened impulsivity and risk of relapse.