16, p < .05), thus reinforcing our findings of low physiological arousal in those more prone to risky substance use. These findings are in line with earlier suggestions that physiological stress response dysregulation in adolescents may signal vulnerability to various kinds of psychopathology ( Stroud et al., 2009). This is the first study to examine the relation between alcohol use and HR in a general adolescent population, therefore, the results are preliminary and must be interpreted cautiously. Our finding that those who drank more portrayed a lower HR during the stress procedure is in line with one finding in adults with a FH of alcoholism (Sorocco et al., 2006), though in contrast

to other similar studies which found increased Target Selective Inhibitor Library order HR in response to unavoidable shock (Finn et al., 1992 and Finn and Pihl, 1987) and a mental arithmetic task (Harden and Pihl, 1995). Further research in this area is needed in order to clarify these contrasting findings. We observed that PS was significantly

and positively related to HR, which confirmed findings from a previous study in adolescents from the general population (Oldehinkel et al., 2011). We did not find a relation between PS and alcohol and tobacco use, corroborating earlier reports of no difference in PS between control subjects and those at risk for a SUD (Finn and Venetoclax cell line Pihl, 1987) Mannose-binding protein-associated serine protease and those exhibiting more externalizing problems (Fairchild et al., 2008). This was in line with our expectations; physiological responses reflect underlying, biological processes, and we would not necessarily expect similar relations to be found with the subjective experience

of a stressor. Physiological and perceived stress are distinct constructs (Oldehinkel et al., 2011), which was substantiated in our finding of a significant and positive, but not strong, correlation between HR and PS. Our observations indicate a relation between tobacco use and HR reactivity. Those who smoked every day showed a blunted HR response to the stressful tasks compared to those who smoked less frequently or not at all. This finding is in line with several findings on adult smokers (Girdler et al., 1997, Phillips et al., 2009, Roy et al., 1994, Sheffield et al., 1997 and Straneva et al., 2000) though is in contrast to other studies (Back et al., 2008, Childs and de Wit, 2009, Hughes and Higgins, 2010, Kirschbaum et al., 1993, Perkins et al., 1992 and Tersman et al., 1991). While two studies examining HR reactivity in low versus high frequency tobacco users found no difference between these groups (both portrayed attenuated responses), we found that adolescents who smoked less frequently did not differ significantly from those who had never smoked. It is possible that in adolescents, underlying variation of the ANS is only evident in those who use tobacco more frequently.