We have hypothesized that nicotine has two effects on reinforcement; it increases the probability of responses resulting in nicotine delivery (primary reinforcement) and enhances the apparent reward value of non-nicotine reinforcers (reinforcement enhancing effect). The present studies investigated two predictions generated by this hypothesis: 1) that the reinforcement enhancing effect will depend on apparent stimulus reward value, and 2) that the temporal profile of this effect would depend on the pharmacological profile of nicotine. In Experiment 1, rats were trained to lever press for one of two audio-visual stimuli that differed in their intrinsic reinforcing value and then the effect of presession nicotine (0.4 mg/kg base) or saline injections was tested. The stimulus that supported very low rates of operant responding displayed smaller increases in responding after pre-session injections of nicotine. In Experiment 2 the effect of nicotine injected 5 min before the session was compared to the effect of nicotine injected 1 h after the session using the more reinforcing stimulus condition from the first experiment. A control group received only vehicle injections. In contrast to nicotine injected just prior to the session, post-session injections of nicotine had no detectable effect on responding for the more reinforcing stimulus. These results indicate that the reinforcement enhancing action of nicotine depends on the intensity of the primary reinforcer and that enhanced reinforcement by nicotine depends on coincident access to a stimulus with reinforcing properties. IntroductionTobacco dependence is a syndrome characterized by subjective drug liking, perseverative drug taking (difficulty quitting), a persistent profile of relapse, and physiological symptoms of tolerance and withdrawal (American Psychiatric Association 2000). Although tobacco dependence has been attributed almost exclusively to the pharmacological action of nicotine (USDHHS 1988), many investigators have recently suggested "nicotine is not enough" (Rose 2006; see also Caggiula et al. 2001). This statement gains credence when the defining features of nicotine dependence are weighed against those of other drug dependence syndromes. For example, the difficulty quitting and rate of relapse associated with smoking is comparable to † Corresponding Author: Matthew I. Palmatier, Department of Psychology, 3137 Sennott Square, 210 S. Bouquet St, University of Pittsburgh, Pittsburgh, PA 15260, 412-624-7345 (Office), 412-624-8558 (Fax), mip16@pitt.edu Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Henni...

Many decisions related to cigarette smoking require people in an affectively neutral, or "cold," state to predict how they will feel or behave when in a craving, or "hot," state. Research in other domains has revealed that individuals in cold states often underestimate the impact of being in a hot state on their own future behavior. In a study testing whether this is true of cigarette craving, 98 smokers were assigned to one of three conditions: hot (during a high-craving first session, they made predictions about a high-craving state in a second session), cold (during a low-craving first session, they made predictions about a high-craving state in a second session), and comparison (they experienced a high-craving session only). As predicted, in contrast to smokers in the hot group, smokers in the cold group underpredicted the value they would place on smoking during the second session. Results support the existence of a cold-to-hot empathy gap in smokers and help to explain diverse aspects of tobacco addiction.

Aims This study examined the personality traits of negative emotionality and constraint and the ability to resist drinking during negative affective states as correlates of solitary drinking in adolescence. We hypothesized that higher levels of negative emotionality and lower levels of constraint would predict solitary drinking and that these relationships would be mediated by the ability to resist drinking in response to negative emotions. Design Structural equation modeling was used to fit a path model from the personality traits of negative emotionality and constraint to solitary drinking status through intermediate effects on the ability to resist drinking during negative emotions using cross-sectional data. Setting Clinical and community settings in Pennsylvania, USA. Participants The sample included 761 adolescent drinkers (mean age = 17.1). Measurements Adolescents completed the Lifetime Drinking History, the Multidimensional Personality Questionnaire, the Constructive Thinking Inventory and the Situational Confidence Questionnaire. Findings The path model provided a good fit to the data. The association between trait negative emotionality and solitary drinking was fully mediated by adolescents' ability to resist drinking during negative affective states (b = 0.05, P = 0.01). In contrast, constraint had a direct effect on solitary drinking (odds ratio (OR) = 0.79, b = –0.23, P<0.01), as well as an indirect effect through the ability to resist drinking during negative affective states (b = –0.03, P = 0.02). Conclusions The ability to resist drinking while experiencing negative feelings or emotions may be an important underlying mechanism linking trait negative emotionality (a tendency toward depression, anxiety and poor reaction to stress) and constraint (lack of impulsiveness) to adolescent solitary drinking.

Background Adolescent substance use treatment outcome research generally shows small to moderate effects in reducing substance use, with no specific “brand” of treatment emerging as clearly superior to any other, and treatment gains that fade over time. The relatively weak and temporary effects of treatment call for improving the potency and durability of intervention effects. In response to this call, this critical narrative review summarizes research on mechanisms of change for both adults and adolescents in substance use treatment, with a particular focus on reviewing what is known regarding “how” adolescent substance use treatment works. Methods A comprehensive review of the adolescent (ages 11–18) substance use treatment literature was conducted to identify empirical studies that examined mediators of intervention effects. Relevant databases (e.g., PsychINFO, Medline) were searched using key words (e.g., “mediator”), and relevant articles from reference sections of identified studies and review papers were considered. Results Studies of mechanisms of psychotherapy change are rare in the adult, and particularly adolescent, substance use treatment outcome literature. The four adolescent studies that examined substance use treatment mechanisms found that positive social support, motivation to abstain, and positive parenting behaviors mediated treatment effects. To date, research has not supported therapy-specific mechanisms of change, finding instead that “common” processes of change largely account for improvements in outcome across distinct “brands” of treatment. Conclusions The lack of empirical support for treatment-specific mechanisms of change may be due to the need for greater precision in defining and measuring treatment-specific causal chains. Future directions include neuroscience approaches to examining changes in brain functioning that are associated with treatment response and recovery and examining mechanisms in adaptive treatment designs, which can accommodate individual differences in targets for intervention and response to treatment.

Type 2 Diabetes Mellitus (T2DM) and obesity are linked to specific patterns of subcortical brain atrophy and decreased microstructural integrity of white matter. Fifteen adolescents (12-21-years-old, 80% Caucasian, 15% African American, mean BMI=32)-five with T2DM confirmed by oral glucose tolerance test, five matched obese adolescent controls without diabetes (OBCN), and five matched (race, sex) normal-weight controls (NWCN)-underwent Magnetic Resonance Imaging (MRI) for the collection of gray matter volume and white matter integrity. Analyses of Variance (ANOVAs) of the neuroimaging data revealed significant differences in caudate nucleus volume [F(2,12)=7.79, p<0.05] such that the normal-weight group had significantly greater volume than the obese and T2DM groups (NWCN>OBCN, p=0.020; OBCN>T2DM, p=0.042; and NWCN>T2DM; p=0.003) after controlling for participant Body Mass Index (BMI). Similarly, there was a main effect for the volume of the thalamus [F(2,12)=4.39, p<0.05] with greater volume for both the NWC and the OBC groups in comparison to the T2DM group (NWC>T2DM, p=0.020; OBC>T2DM; p=0.040). Finally, an examination of white matter integrity among the three groups illustrated a pattern of white matter integrity reduction between normal-weight participants and both obese controls and T2DM participants, with T2DM demonstrating the greatest deficit in functional anisotropy (FA) volume, but these results were not significant after further controlling for BMI. Results from the current pilot study illuminate a host of brain morphology differences between youth with T2DM, obese youth, and normal-weight controls; future research with a larger sample size is critical.