Early life adversity and substance use: The mediating role of mood and the moderating role of impulsivity

INTRODUCTION

Early life adversity (ELA) is a risk factor for substance use and misuse, and multiple factors mediate and moderate this association. We examined whether moods mediate the relationships between ELA and nicotine use, cannabis use, and co-use, and whether these mediation effects varied as a function of delay discounting.

METHODS

A total of 2555 adults completed a delay discounting task and responded to questions related to demographics, ELA, mood, and substance use. Data were analyzed using Pearson correlations and moderated mediation using Hayes' PROCESS macro (V3.4, Model 15).

RESULTS

ELA was positively associated with cannabis use, nicotine use, co-use of both substances, depressed and stressed moods, and it was negatively associated with positive mood. While cannabis use was associated negatively with stressed and depressed moods and positively with positive mood, nicotine use was associated negatively with positive mood. Moderated mediation analyses indicated that positive mood mediated the relationship between ELA and cannabis use for those with average and above average delay discounting. Positive mood also mediated the relationship between ELA and co-use among those with above average delay discounting.

CONCLUSION

The results suggest that ELA's associations with cannabis use and cannabis-nicotine co-use may be partially attributable to ELA's effects on positive mood among those who are predisposed to moderately to highly impulsive decision making.

Initial evaluation of domain-specific episodic future thinking on delay discounting and cannabis use

Episodic Future Thinking (EFT), mental simulation of personally relevant and positive future events, may modulate delay discounting (DD) in cannabis users. Whether EFT impacts cannabis use, whether DD mediates this effect, and whether EFT can be enhanced by prompting future events across specific life domains is unknown. Active, adult cannabis users (n = 90) recruited from Amazon mTurk and Qualtrics Panels were administered an Episodic Specificity Induction (ESI) to enhance quality of imagined events before being randomized to EFT, domain-specific-EFT (DS-EFT), or Episodic Recent Thinking (ERT). All participants created four, positive life events; DS-EFT participants imagined social, leisure, health, and financial events. Event-quality ratings were assessed (e.g., enjoyment). DD was assessed at baseline (Day 1), post-intervention (Days 2-4), and follow-up (Days 9-12). Cannabis use was assessed at baseline and follow-up. Differences in change in days and grams of cannabis use between conditions and mediation of changes in use by DD were examined. No differences in DD were observed between conditions. DS-EFT, but not EFT, showed significantly greater reductions in grams (d = .54) and days of cannabis use (d = .50) than ERT. DS-EFT and EFT demonstrated significantly greater event-quality ratings than ERT (ds > .55). EFT-based interventions showed potential for reducing cannabis use. Unexpectedly, effects on DD did not mediate this effect. Further testing with larger samples of cannabis users is needed to better understand EFT's mechanisms of action and determine optimal implementation strategies. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Associations of cannabis product source and subsequent cannabis use among adolescents

BACKGROUND

Cannabis is obtained from a variety retail and illicit sources, with unknown implications for youth cannabis use. This study assessed whether source of obtaining cannabis was associated with future cannabis use among adolescents.

METHODS

High-schoolers (N = 835) completed 3 semiannual surveys, reporting use of 7 cannabis sources (i.e., free, bought from someone, from an online dispensary, with a [valid/invalid] medical card, self-grown, or other; separate dichotomous exposure variables) at wave 1 (n = 621; M[SD] age=17.14[.40]) or wave 2 (n = 622; M[SD] age=17.51[.39]). Past-6-month (yes/no) and number of past-30-day (0-30) non-medical use of any cannabis product, combustible, edible, and vaporized cannabis, blunts, and concentrates (i.e., dabs) were reported at waves 2-3. Random-effect time-lagged repeated-measures regression was used to test longitudinal associations of youth's cannabis source (waves 1-2; time-varying exposure) with cannabis use outcomes 6 months later (waves 2-3).

RESULTS

Most youth (72.1%) received cannabis for free; 50.9% bought cannabis from someone, 15.9% used a valid medical card at a brick-and-mortar dispensary, and 3.9% grew cannabis. Buying cannabis from someone (OR=1.46, 95% CI: 1.07-1.99, p = .02) or using a valid medical card (OR=1.99, 95% CI: 1.20-3.31, p = .008) conferred greater odds of any cannabis product use 6 months later. Buying from someone predicted subsequent past-30-day use frequency (RR=1.25, 95% CI:1.05-1.48, p = .01). Some associations between particular cannabis sources and products were observed.

CONCLUSIONS

Adolescents may access cannabis from several sources. Those who purchase cannabis illicitly from someone or from a brick-and-mortar dispensary using a valid medical card may be at increased risk for more persistent and frequent patterns of non-medical cannabis use.

Characterizing cannabis use reduction and change in functioning during treatment: Initial steps on the path to new clinical endpoints

Reduction-based cannabis use endpoints are needed to better evaluate treatments for cannabis use disorder (CUD). This exploratory, secondary analysis aimed to characterize cannabis frequency and quantity reduction patterns and corresponding changes in psychosocial functioning during treatment. We analyzed 16 weeks (4 prerandomization, 12 postrandomization) of data (n = 302) from both arms of a randomized clinical trial assessing pharmacotherapy for CUD. Cannabis consumption pattern classes were extracted with latent profile modeling using self-reported (a) past-week days used (i.e., frequency) and (b) past-week average grams used per using day (i.e., quantity). Changes in mean Marijuana Problem Scale (MPS) and Hospital Anxiety and Depression Scale (HADS) scores were examined among classes. Urine cannabinoid levels were examined in relation to self-reported consumption as a validity check. Two-, three-, four-, and five-class solutions each provided potentially useful conceptualizations of associations between frequency and quantity. Regardless of solution, reductions in MPS scores varied in magnitude across classes and closely tracked class-specific reductions in consumption (e.g., larger MPS reduction corresponded to larger frequency/quantity reductions). Changes in HADS scores were less pronounced and less consistent with consumption patterns. Urine cannabinoid levels closely matched class-specific self-reported consumption frequency. Findings illustrate that frequency and quantity can be used in tandem within mixture model frameworks to summarize heterogeneous cannabis use reduction patterns that may correspond to improved psychosocial functioning. Going forward, similar analytic strategies applied to alternative metrics of cannabis consumption may facilitate construction of useful reduction-based clinical endpoints. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Correlates of continued cannabis use during pregnancy

BACKGROUND

Cannabis use is increasingly common among pregnant women despite concern that it may be linked to adverse maternal and infant outcomes. Determining whether variables associated with cannabis use predict whether women continue or quit using during pregnancy may inform strategies to reduce prenatal use.

METHODS

Pregnant women who regularly used cannabis before pregnancy (n = 296) were recruited via Facebook. After finding out they were pregnant, 41 % reported quitting, 13 % quit then relapsed, 32 % reduced use, and 15 % continued use at the same rate. Differences among these four cannabis use status groups (quit, relapsed, reduced, continued) in sociodemographics, cannabis use, cigarette use, perceived risk/benefit, delay discounting, and communications about cannabis with their doctor were assessed.

RESULTS

Compared to those who quit, continuing use during pregnancy was associated with being unemployed (Relative Risk (RR) = .32, 95 %CI [.13, .78]), using cigarettes pre-pregnancy (RR = 3.43, 95 %CI [1.32, 8.94]), being in an earlier trimester (RR = 4.38, 95 %CI [1.18, 16.23]), less perceived risk (RR = .79, 95 %CI [.74, .85]), and more days per week of use pre-pregnancy (RR = .10, 95 %CI [.01, .84]). Unintended pregnancy, shorter time to cannabis use after waking pre-pregnancy, using cannabis more times per day pre-pregnancy, and greater perceived benefits of use had significant bivariate associations with continued use during pregnancy, but did not retain significance in a multinomial model.

CONCLUSIONS

Identification of these correlates provides potential targets for prevention of or intervention for prenatal cannabis use. However, much more research is needed to understand prenatal cannabis use and its effects in order to better educate women and healthcare providers, and to design optimal public health strategies.

Evaluating cannabis use risk reduction as an alternative clinical outcome for cannabis use disorder

OBJECTIVE

Abstinence is rarely achieved in clinical trials for cannabis use disorder (CUD). Cannabis reduction is associated with functional improvement, but reduction endpoints have not been established, indicating a need to identify and validate clinically meaningful reduction endpoints for assessing treatment efficacy.

METHOD

Data from a 12-week double-blind randomized placebo-controlled medication trial for cannabis cessation (NCT01675661) were analyzed. Participants (N = 225) were treatment-seeking adults, M = 30.6 (8.9) years old, 70.2% male, and 42.2% Non-White, with CUD who completed 12 weeks of treatment. Frequency (days of use per week) and quantity (grams per using day) were used to define high-, medium-, and low-risk levels. Anxiety and depression were assessed using the Hospital Anxiety and Depression Scale and cannabis-related problems were assessed using the Marijuana Problems Scale. General linear models for repeated measures tested associations between the magnitude of risk reduction and functional outcomes from baseline (BL) to end-of-treatment (EOT).

RESULTS

Cannabis risk levels were sensitive to reductions in use from BL to EOT for frequency- (χ² = 19.35, p = .004) and quantity-based (χ² = 52.06, p < .001) metrics. Magnitude reduction in frequency-based risk level was associated with magnitude decrease in depression (F = 2.76, p = .043, η_p² = .04), anxiety (F = 3.70, p = .013, η_p² = .05), and cannabis-related problems (F = 8.95, p < .001, η_p² = .12). Magnitude reduction in quantity-based risk level was associated with magnitude decrease in anxiety (F = 3.02, p = .031, η_p² = .04) and cannabis-related problems (F = 3.24, p = .023, η_p² = .05).

CONCLUSIONS

Cannabis use risk levels, as operationalized in this study, captured reductions in use during a clinical trial. Risk level reduction was associated with functional improvement suggesting that identifying risk levels and measuring the change in levels over time may be a viable and clinically meaningful endpoint for determining treatment efficacy. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

The importance of psychology for shaping legal cannabis regulation

Different patterns of cannabis use can be traced directly back to different interactions between 2 types of variables: pharmacological and environmental. As legal cannabis expands in the U.S. and around the world, state and national regulatory agencies are gaining control over these variables. Specifically, regulatory agencies are increasingly capable of altering (a) the pharmacological properties of cannabis products and (b) the way these products are distributed to the population. Consequently, cannabis regulatory agencies are in a unique position to use evidence from psychological science to alter cannabis consumption patterns in ways that mitigate potential harm to public health. However, most state-level legal cannabis regulatory systems in the U.S. are not yet evidence-based or public health-oriented. This applied review and commentary draws on evidence from the psychological science literature to help regulators better understand the types of behaviors they must address and guide empirically supported regulation of THC-laden cannabis, whether used putatively for medical or recreational reasons. This review is organized into 3 parts that correspond to the 3 primary agents within the cannabis regulation ecosystem: (a) the cannabis consumer, (b) the cannabis industry, and (c) the cannabis regulatory agency. Within this structure, the review addresses critical psychological variables that drive cannabis consumer and industry behaviors and discusses how regulatory agencies can use this information to protect public health. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

The Effects of Cannabis Use Frequency and Episodic Specificity Training on the Recall of Specific and Rewarding Events

Background: Growing evidence implicates subjective episodic memory, the retrieval of detailed, integrated, and personally relevant past events, as a marker of cognitive vulnerability in mental disorders. Frequent and problematic cannabis use is associated with deficits in objective episodic memory (verbal memory), but the relationship between subjective episodic memory deficits and frequency of cannabis use is unknown. Further, whether a brief intervention designed to enhance the specificity of event retrieval, such as the Episodic Specificity Induction (ESI), might effectively target such deficits among regular cannabis users is unexamined. This study was designed to examine subjective episodic memory as a potential marker of cognitive vulnerability among frequent cannabis users. Methods: Active cannabis users (n = 133) recruited from Amazon Mechanical Turk or Qualtrics Panels were randomized to receive an ESI-control or ESI session and were separated into those who used cannabis 1-25 days in the past month (low to moderate frequency group) and those who used 26-30 days (high frequency group), which facilitated a low to moderate use/ESI-control group (n = 78), low to moderate use/ESI group (n =15), high-use/ESI-control group (n = 20), and high-use/ESI group (n = 20). Following the ESI or ESI-control intervention, participants selected four, positive events from the prior day, described the who, what, and where of the events, and rated how specific (vividness) and rewarding (enjoyable, importance, and exciting) each event was on a 0-100 scale. Four two-way ANCOVAs (demographics and problematic cannabis use covariates) were performed to examine the effects of frequency of cannabis use group and ESI group on the specificity and reward ratings. Results: Lower vividness and excitement ratings were reported for those with high relative to low to moderate cannabis use frequency patterns (p < 0.05). Those who received ESI reported greater vividness, excitement, and importance ratings than the ESI-control group (p < 0.01). No significant interactions between frequency and ESI were found. Conclusion: Findings from the current exploratory study provide initial evidence suggesting that more frequent cannabis use may be associated with the retrieval of less specific and rewarding events relative to less frequent users. Further, ESI may improve such deficits. Future studies that recruit larger and more clinically serious samples of cannabis users appear warranted.

Sifting through the weeds: Relationships between cannabis use frequency measures and delay discounting

BACKGROUND

Delay Discounting (DD) relates to more frequent cannabis use, but results are variable, potentially because of variations in whether integrated or single-item measures are used, and whether the timeframe of measures is narrow or broad. Explicating the relationship between DD and cannabis use may result from comparing use indices that vary on these characteristics.

METHODS

This online study of current cannabis users (n = 1,800) assessed DD and three cannabis use frequency items: number of days of use in the past month, times used per day, and weekly-monthly use. A fourth index derived with Latent Class Analysis (LCA) integrated days per month and times per day to try to better characterize frequency patterns. Effect sizes reflecting relations between cannabis use frequency indices and DD were compared.

RESULTS

Three frequency classes emerged from the LCA (Low-Moderate-High). DD was significantly associated with times per day (r = 0.11, d = 0.21), days of use (r = 0.09, d = 0.18), and the LCA index (r = 0.06, d = 0.13), but not weekly-monthly use (r = 0.04, d = 0.09). Times per day was more strongly related to DD than LCA classes (p < 0.01) and weekly-monthly use (p < 0.05), but not days of use (p = 0.66). Days of use exhibited a stronger relationship with DD than weekly-monthly use (p < 0.001), but not LCA classes (p = 0.06).

CONCLUSIONS

Cannabis use frequency measures with narrower timeframes may demonstrate stronger positive relationships to DD. The LCA index did not improve the relationship between frequency and DD, potentially because of shared variance between use days and times per day. Specific characteristics of cannabis use frequency may be particularly indicative of excessive DD.

On the discounting of cannabis and money: Sensitivity to magnitude vs. delay

BACKGROUND

While using most drugs of abuse is associated with higher than control rates of delay discounting, cannabis use may be the exception. As such, between-commodity differences in delay discounting (i.e., money vs. cannabis) have not been thoroughly examined. We examined these between-commodity differences using modern analytic techniques to disentangle effects of subjects' sensitivity to magnitude and delay as potential drivers of any obtained delay discounting rate differences.

METHOD

; Fifty-eight college students (n = 33 cannabis users, n = 25 non-users) completed a monetary delay discounting task - with the cannabis users completing the cannabis problems questionnaire as well a delay discounting of cannabis task- in an on-campus laboratory.

RESULTS

Responding between groups differed on the cannabis problems questionnaire, but not on delay discounting of monetary outcomes. Cannabis users, however, discounted cannabis at higher rates than money. Multilevel logistic regression revealed that these between-commodity delay discounting differences were due to subjects' differential sensitivity to the magnitude of these two commodities, rather than sensitivity to delay to receiving these commodities.

CONCLUSIONS

Although differences in delay discounting rate were not obtained between students that did and did not use cannabis, cannabis users did discount cannabis at higher rates than they did money - suggesting considerable generality of the between commodity differences in delay discounting obtained elsewhere. The current between-commodity delay discounting differences appear to be driven by differential sensitivity to the reinforcer magnitudes presented in each task - a finding that awaits replication across other comparisons before statements about generality can be made.

Persisting on the past: Cross-sectional and prospective associations between sunk cost propensity and cannabis use

Prevalence of cannabis use in the United States continues to rise, and 30% of cannabis users eventually meet criteria for Cannabis Use Disorder (CUD). One response to this problem is to develop decision-making constructs that indicate vulnerability to CUD that might not be gleaned from diagnostic criteria. Unfortunately, there is limited evidence that decision-making constructs consistently relate to cannabis use. Interestingly, those who exhibit the sunk cost bias, an overgeneralized tendency to persist based on past investment, and those who use cannabis, both tend to focus on the past and perseverate more than their counterparts. Despite this overlap, no studies have assessed whether the sunk cost bias is positively associated with cannabis use. In 2 experiments with undergraduates, relations between cannabis use and the propensity to engage in the sunk cost bias were examined using negative binomial models. Experiment 1 (n = 46) evaluated the association between sunk cost bias propensity (using hypothetical costs and rewards) and frequency of cannabis use over the past 30 days. Greater sunk cost propensity was associated with more frequent cannabis use after controlling for demographics and alcohol use. In Experiment 2 (n = 103), more frequent cannabis use during a 6-week follow-up period was predicted by greater sunk cost propensity at baseline (using a real cost and reward-based task), independently and after controlling for mental health symptoms, alcohol use, and demographics. These findings provide preliminary evidence that a propensity to exhibit the sunk cost bias may be an important feature associated with cannabis use. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Greater delay discounting and cannabis coping motives are associated with more frequent cannabis use in a large sample of adult cannabis users

BACKGROUND

Self-regulation deficits expressed through a decreased ability to value future rewards (delay discounting (DD)) and impaired emotion regulation (negative urgency (NU), cannabis coping motives (CCM), and anxiety sensitivity (AS)) relate to more frequent or problematic cannabis use. However, there is a need to better understand how self-regulation and emotion regulation constructs reflect competition between deliberative and reactive systems that drive individual differences in cannabis use patterns. Further, few studies assess frequency of cannabis use within and across days of use, which may obscure differentiation of individual differences.

METHODS

In a large national sample of 2545 cannabis users, Latent Class Analysis was used to derive participant sub-classes based on two frequency indices, self-reported cannabis use days and times cannabis was used per day. Three classes emerged: Low (1-9 days/month, 1 time/day; 23 %), moderate (10-29 days/month, 2-3 times/day; 41 %), and high (30 days/month, ≥4 times/day; 36 %). Relationships among frequency classes and emotional regulation and impulsivity were assessed with a multinomial logistic regression.

RESULTS

Higher frequency use was associated with greater DD (χ2 = 6.0, p = .05), greater CCM (χ2 = 73.3, p < .001), and lower cognitive AS (χ2 = 12.1, p = .002), when controlling for demographics, tobacco use, and number of cannabis administration methods. Frequency class and NU were not significantly associated.

CONCLUSIONS

Identifying meaningful patterns of cannabis use may improve our understanding of individual differences that increase risk of frequent or problematic cannabis use. Excessive delay discounting and using cannabis to cope with negative affect may be relevant targets for treatments designed to reduce cannabis use.

A web-based episodic specificity and future thinking session modulates delay discounting in cannabis users

Episodic future thinking (EFT), a brief intervention involving mental simulation of positive future events, improves delay discounting (DD) in nicotine and alcohol dependent individuals. This study is the first to assess effects of a single-session, online episodic training (ET) on constructs that might impact cannabis use and cannabis use disorder. A sample of 200 active cannabis users recruited via Amazon Mechanical Turk were randomized to an EFT group (n = 102) or an episodic recent thinking control group (ERT; n = 98). A novel episodic specificity induction (ES) was included to enhance quality of episodic thinking for the ET group, and an ES attention control was provided to the ERT group (control training group; CT). Quality and manipulation ratings of event excitement, vividness, importance, and enjoyment of trainings were collected in addition to DD tasks (gains and losses) and readiness to change cannabis use. The ET group reported higher overall quality and manipulation ratings than did the CT group (p < .001, d = 0.79). DD of gains was lower in the ET relative to those of the CT group after controlling for relevant variables (p = .003, d = 0.48), unlike DD of losses (p = .50, d = 0.11). The ET group showed larger pre/post increases in readiness to change, but they were not statistically significant (p = .069, d = 0.26). These effects, following a session of online ET, suggests that ET may positively impact factors related to reduction in cannabis use. Differential effects of EFT and ES components on DD and the development of ET as an adjunctive mHealth intervention targeting reduction in cannabis use appears warranted. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

An update on cannabis use disorder with comment on the impact of policy related to therapeutic and recreational cannabis use

Confusion and controversy related to the potential for cannabis use to cause harm, or alternatively to provide benefit, continues globally. This issue has grown in intensity and importance with the increased recognition of the public health implications related to the escalation of the legalization of cannabis and cannabinoid products. This selective overview and commentary attempt to succinctly convey what is known about one potential consequence of cannabis use, the development of cannabis use disorder (CUD). Such knowledge may help guide a reasonable and objective public health perspective on the potential impact of cannabis use and CUD. Current scientific data and clinical observation strongly support the contention that cannabis use, like the use of other substances such as alcohol, opioids, stimulants, and tobacco, can develop into a use disorder (addiction) with important clinical consequences. Epidemiological data indicate that the majority of those who use cannabis do not have problems related to their use, but a substantial subset (10-30%) do report experiencing symptoms and consequences consistent with a CUD. Treatment seeking for CUD comprises a substantial proportion of all substance use treatment admissions, yet treatment response rates show much room for improvement. Changing cannabis policies related to its therapeutic and recreational use are likely to impact the development of CUD and its course; however, definitive data on such effects are not yet available. Clearly, the development of more effective prevention and treatment strategies is needed for those vulnerable to developing a CUD and for those with a CUD.

5-Fluorouracil impairs attention and dopamine release in rats

Chemotherapy related cognitive impairment (CTRC; "chemobrain") is a syndrome that is associated with the impairment of various aspects of cognition, including executive function, processing speed, and multitasking. The role of neurotransmitter release in the expression of cognitive impairments is not well known. In this work we employed a newly developed behavioral paradigm to measure attentional shifting, a fundamental component of executive function, in rats treated with 5-fluorouracil (5-FU), a commonly used cancer chemotherapy agent. We found that one and two weeks of 5-FU treatment significantly impaired attentional shifting compared to baseline, while saline treatment had no effect. Post-mortem analysis of these rats revealed that 5-FU caused a significant overall decrease in dopamine release as well. Collectively, these results demonstrate the feasibility of our attentional shifting paradigm for evaluating the cognitive effects of chemotherapy treatment. Moreover, these results support the need for additional studies to determine if impaired dopamine release plays a role in chemobrain.

Delay discounting as impaired valuation: Delayed rewards in an animal obesity model

Obesity is a major public health problem, which, like many forms of addiction, is associated with an elevated tendency to choose smaller immediate rather than larger delayed rewards, a response pattern often referred to as excessive delay discounting. Although some accounts of delay discounting conceptualize this process as impulsivity (placing the emphasis on overvaluing the smaller immediate reward), others have conceptualized delay discounting as an executive function (placing the emphasis on delayed rewards failing to retain their value). The present experiments used a popular animal model of obesity that has been shown to discount delayed rewards at elevated rates (i.e., obese Zucker rats) to test two predictions that conceptualize delay discounting as executive function. In the first experiment, acquisition of lever pressing with delayed rewards was compared in obese versus lean Zucker rats. Contrary to predictions based on delay discounting as executive function, obese Zucker rats learned to press the lever more quickly than controls. In the second experiment, progressive ratio breakpoints (a measure of reward efficacy) with delayed rewards were compared in obese versus lean Zucker rats. Contrary to the notion that obese rats fail to value delayed rewards, the obese Zucker rats' breakpoints were (at least) as high as those of the lean Zucker rats.

KU32 prevents 5-fluorouracil induced cognitive impairment

Chemotherapy induced cognitive impairment (i.e. chemobrain) involves acute and long-term deficits in memory, executive function, and processing speed. Animal studies investigating these cognitive deficits have had mixed results, potentially due to variability in the complexity of behavioral tasks across experiments. Further, common chemotherapy treatments such as 5-fluorouracil (5-FU) break down myelin integrity corresponding to hippocampal neurodegenerative deficits and mitochondrial dysfunction. There is little evidence, however, of pharmacological treatments that may target mitochondrial dysfunction. Using a differential reinforcement of low rates (DRL) task combining spatial and temporal components, the current study evaluated the preventative effects of the pharmacological agent KU32 on the behavior of rats treated with 5-FU (5-FU+Saline vs. 5FU+KU32). DRL performance was analyzed the day after the first set of injections (D1), the day after the second set of injections (D7) and the last day of the experiment (D14). The 5FU+KU32 group earned significantly more reinforcers on the DRL task at D7 and D14 than the 5FU+Saline group. Further, the 5FU+KU32 group showed significantly better temporal discrimination. The 5FU+KU32 showed within-group improvement in temporal discrimination from D7 to D14. No significant differences were observed in spatial discrimination, however, those in the 5FU+Saline group responded more frequently on T3 compared to the 5FU+KU32 group, highlighting temporal discrimination differences between groups. The current data suggest that KU32 shows promise in the prevention of chemotherapy induced impairments in temporal discrimination.

Maintained Physical Activity Induced Changes in Delay Discounting

Those who discount the subjective value of delayed rewards less steeply are more likely to engage in physical activity. There is limited research, however, showing whether physical activity can change rates of delay discounting. In a two-experiment series, treatment and maintenance effects of a novel, effort-paced physical activity intervention on delay discounting were evaluated with multiple baseline designs. Using a lap-based method, participants were instructed to exercise at individualized high and low effort levels and to track their own perceived effort. The results suggest that treatment-induced changes in discounting were maintained at follow-up for 13 of 16 participants. In Experiment 2, there were statistically significant group-level improvements in physical activity and delay discounting when comparing baseline with both treatment and maintenance phases. Percentage change in delay discounting was significantly correlated with session attendance and relative pace (min/mile) improvement over the course of the 7-week treatment. Implications for future research are discussed.

Sunk costs, psychological symptomology, and help seeking

Individuals often allow prior investments of time, money or effort to influence their current behavior. A tendency to allow previous investments to impact further investment, referred to as the sunk-cost fallacy, may be related to adverse psychological health. Unfortunately, little is known about the relation between the sunk-cost fallacy and psychological symptoms or help seeking. The current study used a relatively novel approach (i.e., Amazon.com’s Mechanical Turk crowdsourcing [AMT] service) to examine various aspects of psychological health in internet users (n = 1053) that did and did not commit the sunk-cost fallacy. In this observational study, individuals logged on to AMT, selected the “decision making survey” amongst the array of currently available tasks, and completed the approximately 200-question survey (which included a two-trial sunk cost task, the brief symptom inventory 18, the Binge Eating Scale, portions of the SF-8 health survey, and other questions about treatment utilization). Individuals that committed the fallacy reported a greater number of symptoms related to Binge Eating Disorder and Depression, being bothered more by emotional problems, yet waited longer to seek assistance when feeling ill. The current findings are discussed in relation to promoting help-seeking behavior amongst individuals that commit this logical fallacy.

Impaired Brain Dopamine and Serotonin Release and Uptake in Wistar Rats Following Treatment with Carboplatin

Chemotherapy-induced cognitive impairment, known also as “chemobrain”, is a medical complication of cancer treatment that is characterized by a general decline in cognition affecting visual and verbal memory, attention, complex problem solving skills, and motor function. It is estimated that one-third of patients who undergo chemotherapy treatment will experience cognitive impairment. Alterations in the release and uptake of dopamine and serotonin, central nervous system neurotransmitters that play important roles in cognition, could potentially contribute to impaired intellectual performance in those impacted by chemobrain. To investigate how chemotherapy treatment affects these systems, fast-scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes was used to measure dopamine and serotonin release and uptake in coronal brain slices containing the striatum and dorsal raphe nucleus, respectively. Measurements were taken from rats treated weekly with selected doses of carboplatin and from control rats treated with saline. Modeling the stimulated dopamine release plots revealed an impairment of dopamine release per stimulus pulse (80% of saline control at 5 mg/kg and 58% at 20 mg/kg) after 4 weeks of carboplatin treatment. Moreover, V_max, the maximum uptake rate of dopamine, was also decreased (55% of saline control at 5 mg/kg and 57% at 20 mg/kg). Nevertheless, overall dopamine content, measured in striatal brain lysates by high performance liquid chromatography, and reserve pool dopamine, measured by FSCV after pharmacological manipulation, did not significantly change, suggesting that chemotherapy treatment selectively impairs the dopamine release and uptake processes. Similarly, serotonin release upon electrical stimulation was impaired (45% of saline control at 20 mg/kg). Measurements of spatial learning discrimination were taken throughout the treatment period and carboplatin was found to alter cognition. These studies support the need for additional neurochemical and behavioral analyses to identify the underlying mechanisms of chemotherapy-induced cognitive disorders.

A multiple-stimulus-without-replacement assessment for sexual partners: Purchase task validation

The current study developed and tested a multiple-stimulus-without-replacement (MSWO) assessment for potential sexual partners for use in research on human immunodeficiency virus. College students (N = 41) first completed an MSWO assessment and then completed a hypothetical purchase task for encounters with partners identified by the MSWO as high, median, and low preference. Overall, hypothetical purchase task responding was consistent with that from the MSWO, in that the highest valuation was observed for the high-preference partner and the lowest for the low-preference partner. Potentially interesting individual differences in purchase task responding, however, were obtained; some subjects showed differentiated responding among the 3 preference levels (n = 15), whereas others similarly valued high- and median-preference partners (n = 5), and others similarly valued low- and median-preference partners (n = 18).

Concurrent progressive ratio schedules: Effects of reinforcer probability on breakpoint and response allocation

Although progressive ratio (PR) schedules have been used to explore effects of a range of reinforcer parameters (e.g., magnitude, delay), effects of reinforcer probability remain underexplored. The present project used independently progressing concurrent PR PR schedules to examine effects of reinforcer probability on PR breakpoint (highest completed ratio prior to a session terminating 300s pause) and response allocation. The probability of reinforcement on one lever remained at 100% across all conditions while the probability of reinforcement on the other lever was systematically manipulated (i.e., 100%, 50%, 25%, 12.5%, and a replication of 25%). Breakpoints systematically decreased with decreasing reinforcer probabilities while breakpoints on the control lever remained unchanged. Patterns of switching between the two levers were well described by a choice-by-choice unit price model that accounted for the hyperbolic discounting of the value of probabilistic reinforcers.

On the time course of rapid and repeatable response induction

As reinforcers are delivered for a particular response, that response increases. Other similar responses also increase, with the extent to which this increase is seen being positively related to the similarity between the responses. This process, called induction, is pronounced during initial response acquisition, and dissipates as the target response is established. The present experiment examined this process in a paradigm wherein responses to one of five nose poke receptacles results in reinforcement for six sessions in each condition and the target location changes between conditions. Consistent patterns of induction were seen across conditions, with patterns of induction dissipating within each condition.