The effects of oral d-amphetamine on impulsivity in smoked and intranasal cocaine users

Acute effects of amphetamine and related psychostimulants on impulsivity: a systematic review of clinical trials

Evidence for acute amphetamine effects on behavioural impulsivity in healthy populations remains elusive and, at times, mixed. This review collates and reviews the clinical literature on the acute effects of amphetamines on measures of behavioural impulsivity in healthy adults. Randomised and placebo-controlled clinical trials that assessed behavioural impulsivity following the administration of an acute dose of amphetamine or a related psychostimulant (including amphetamine analogues and methylphenidate) were eligible for inclusion. The EBSCOHost, SCOPUS, PsychNet, Web of Science and ProQuest databases were searched from inception to 26 April 2021. Study selection, data extraction and the Cochrane risk of bias assessments were conducted by two independent reviewers. Reporting follows PRISMA guidelines, and the review was registered a priori on the PROSPERO database (Registration No: CRD42021249861). A total of 20 studies were included, comprising a total of 737 participants. Overall, results indicate that low-moderate doses of amphetamine and related psychostimulants may improve (i.e., reduce) impulsive responding without compromising performance, reflecting enhanced inhibitory control of behaviour. These effects are mild and appear most pronounced in individuals with high baseline impulsivity. This review highlights the need for greater consistency in behavioural task selection and future high-quality and well-designed studies to address current concerns around growing prescription psychostimulant use and misuse.

Impulsivity in cocaine users compared to matched controls: Effects of sex and preferred route of cocaine use

BACKGROUND

Impulsivity has been identified as playing a role in cocaine use. The purpose of this study was to explore self-report measures of impulsivity in large groups of male and female cocaine users and matched controls and to determine if differences in impulsivity measures within a group of cocaine users related to self-reported money spent on cocaine and route of cocaine use.

METHODS

Eight self-report impulsivity measures yielding 34 subscales were obtained in 230 cocaine users (180 M, 50 F) and a matched group of 119 healthy controls (89 M, 30 F). Correlational analysis of the questionnaires revealed 2 factors: Impulsive Action (Factor 1) consisting of many traditional impulsivity measures and Thrill-seeking (Factor 2) consisting of delay discounting, sensation and thrill seeking.

RESULTS

Sex influenced within group comparisons. Impulsive Action scores did not vary as a function of sex within either group. But, male controls and male cocaine users had greater Thrill-seeking scores than females within the same group. Sex also influenced between group comparisons. Male cocaine users had greater Impulsive Action scores while female cocaine users had greater Thrill-seeking scores than their sex-matched controls. Among cocaine users, individuals who preferred insufflating ("snorting") cocaine had greater Thrill-seeking scores and lower Impulsive Action scores than individuals who preferred smoking cocaine. Individuals who insufflate cocaine also spent less money on cocaine.

CONCLUSIONS

Greater Impulsive Action scores in males and Thrill-seeking scores in females were associated with cocaine use relative to controls.

Rejecting impulsivity as a psychological construct: A theoretical, empirical, and sociocultural argument

We demonstrate through theoretical, empirical, and sociocultural evidence that the concept of impulsivity fails the basic requirements of a psychological construct and should be rejected as such. Impulsivity (or impulsiveness) currently holds a central place in psychological theory, research, and clinical practice and is considered a multifaceted concept. However, impulsivity falls short of the theoretical specifications for hypothetical constructs by having meaning that is not compatible with psychometric, neuroscience, and clinical data. Psychometric findings indicate that impulsive traits and behaviors (e.g., response inhibition, delay discounting) are largely uncorrelated and fail to load onto a single, superordinate latent variable. Modern neuroscience has also failed to identify a specific and central neurobehavioral mechanism underlying impulsive behaviors and instead has found separate neurochemical systems and loci that contribute to a variety of impulsivity types. Clinically, these different impulsivity types show diverging and distinct pathways and processes relating to behavioral and psychosocial health. The predictive validity and sensitivity of impulsivity measures to pharmacological, behavioral, and cognitive interventions also vary based on the impulsivity type evaluated and clinical condition examined. Conflation of distinct personality and behavioral mechanisms under a single umbrella of impulsivity ultimately increases the likelihood of misunderstanding at a sociocultural level and facilitates misled hypothesizing and artificial inconsistencies for clinical translation. We strongly recommend that, based on this comprehensive evidence, psychological scientists and neuroscientists reject the language of impulsivity in favor of a specific focus on the several well-defined and empirically supported factors that impulsivity is purported to cover. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Cocaine addiction severity exacerbates the negative association of lifetime lead exposure with blood pressure levels: Evidence from a pilot study

BACKGROUND

High blood pressure (BP) is associated independently with cocaine use and lead exposure. It is not known whether cocaine use and lead exposure act jointly to disrupt cardiovascular health.

OBJECTIVE

To determine whether cocaine use modifies the association between cumulative lead levels and elevated BP.

MATERIALS AND METHODS

We measured cumulative tibia lead levels in 35 adults: 20 with cocaine use disorder (CUD) and 15 non-CUD controls using in vivo K-shell X-ray fluorescence. Generalized estimating equation regression determined associations between log2-transformed lead and BP (systolic, diastolic, and mean arterial pressure) and assessed the modifying association of cocaine use (as addiction severity) on the lead-BP relationship, adjusting for age, sex, smoking, and education. Sensitivity analyses included correction for potential selection bias.

RESULTS

Cases and controls differed by sex (%male: 90% vs. 67%), age (50.7 vs. 39.9 years), education (12.8 vs. 14.4 years), and tibia lead (3.50 vs. 2.35 μg/g). Lead was positively associated with systolic (P = 0.01) and diastolic BP (P = 0.01). We observed an interaction between lead and addiction severity on BP (P values for systolic BP: 0.01, diastolic BP: 0.003, and mean arterial BP: <0.0001); the association was stronger among individuals with more severe cocaine addiction: Systolic BP: Est.: 17.89, 95% confidence interval (CI): 9.52; 26.26, diastolic BP Est.: 17.89, 95% CI: 7.33; 13.79, mean arterial BP: Est.: 13.09, 95% CI: 10.34; 15.83.

CONCLUSIONS

Lead was adversely associated with BP. This association was strongest among individuals with more severe cocaine addiction. The results from this small pilot study suggest that the interaction between lead and cocaine should be considered in studies of substance abuse-related health outcomes.

The neurobiology of impulsivity and substance use disorders: implications for treatment

Impulsivity is strongly associated with substance use disorders (SUDs). Our review discusses impulsivity as an underlying vulnerability marker for SUDs, and treatment of co-occurring impulsivity in SUDs. Three factors should be considered for the complex relationship between impulsivity and a SUD: (1) the trait effect of impulsivity, centering on decreased cognitive and response inhibition, (2) the state effect resulting from either acute or chronic substance use on brain structure and function, and (3) the genetic and environmental factors (e.g., age and sex) may influence impulsive behavior associated with SUDs. Both subjective and objective measures are used to assess impulsivity. Together, treatment developments (pharmacological, behavioral, and neurophysiological) should consider these clinically relevant dimensions assessed by a variety of measures, which have implications for treatment matching in individuals with SUD. Despite its heterogeneity, impulsivity is a marker associated with SUDs and may be understood as an imbalance of bottom-up and top-down neural systems. Further investigation of these relationships may lead to more effective SUD treatments.

Pharmacotherapies for decreasing maladaptive choice in drug addiction: Targeting the behavior and the drug

Drug addiction can be conceptualized as a disorder of maladaptive decision making in which drugs are chosen at the expense of pro-social, nondrug alternatives. The study of decision making in drug addiction has focused largely on the role of impulsivity as a facilitator of addiction, in particular the tendency for drug abusers to choose small, immediate gains over larger but delayed outcomes (i.e., delay discounting). A parallel line of work, also focused on decision making in drug addiction, has focused on identifying the determinants underlying the choice to take drugs over nondrug alternatives (i.e., drug vs. nondrug choice). Both tracks of research have been valuable tools in the development of pharmacotherapies for treating maladaptive decision making in drug addiction, and a number of common drugs have been studied in both designs. However, we have observed that there is little uniformity in the administration regimens of potential treatments between the designs, which hinders congruence in the development of single treatment strategies to reduce both impulsive behavior and drug choice. The current review provides an overview of the drugs that have been tested in both delay-discounting and drug-choice designs, and focuses on drugs that reduced the maladaptive choice in both designs. Suggestions to enhance congruence between the findings in future studies are provided. Finally, we propose the use of a hybridized, experimental approach that may enable researchers to test the effectiveness of therapeutics at decreasing impulsive and drug choice in a single design.