Psychostimulants As Cognitive Enhancers in Adolescents: More Risk than Reward?

An Adaptation and Validation of Cocaine Craving Questionnaire for Malaysians Who Use Amphetamine-Type Stimulants

Introduction

Cases of amphetamine-type stimulants (ATS) use have been increasing over the past decade. Cravings are considered a causal factor for recurrent relapses in ATS use cases. The absence of questionnaires measuring cravings for ATS in the local population necessitates the creation of one, especially considering the rising number of cases.

Objective

This study aimed to adapt and validate the Cocaine Cravings Questionnaire into a questionnaire suitable for measuring cravings for ATS in the local population.

Methodology

The original questionnaire was adapted by substituting "cocaine" with "ATS". The process involved a back-to-back translation, followed by a round of face and content validation. The participants included people who use drugs (PWUD) with a history of ATS use recruited from rehabilitation centers in Malaysia. A set of questionnaires consisting of demographic items and the adapted ATS Cravings Questionnaire (ATS-CQ) were given.

Results

This cross-sectional study recruited a total of 205 PWUD, mostly single men, with a mean age of 33.32 (s.d.=13.14). The mean age of ATS initiation was 22.89 (s.d.=9.39), with a median duration of ATS use of 60 months (IQR=24.00, 120.00). The adapted questionnaire received a good score for content validation. Unlike the original, this adapted version was found to have only three factors showing good internal consistency, ranging from 0.707 to 0.918 for all three factors. Test-retest reliability also showed good results, with an interclass correlation coefficient of 0.875 (95% CI=0.835, 0.905).

Conclusion

The translated ATS-CQ has been finalized and deemed valid and reliable for use among Malaysian substance users to measure ATS cravings.

The perception of Mandarin speech conveying communicative functions in Chinese heroin addicts

Drug addiction can cause severe damage to the human brain, leading to significant problems in cognitive processing, such as irritability, speech distortions, and exaggeration of negative stimuli. Speech plays a fundamental role in social interaction, including both the production and perception. The ability to perceive communicative functions conveyed through speech is crucial for successful interpersonal communication and the maintaining good social relationships. However, due to the limited number of previous studies, it remains unclear whether the cognitive disorder caused by drug addiction affects the perception of communicative function conveyed in Mandarin speech. To address this question, we conducted a perception experiment involving sixty male participants, including 25 heroin addicts and 35 healthy controls. The experiment aimed to examine the perception of three communicative functions (i.e., statement, interrogative, and imperative) under three background noise conditions (i.e., no noise, SNR [Signal to Noise Ratio] = 10, and SNR = 0). Eight target sentences were first recorded by two native Mandarin speakers for each of the three communicative functions. Each half was then combined with Gaussian White Noise under two background noise conditions (i.e., SNR = 10 and SNR = 0). Finally, 48 speech stimuli were included in the experiment with four options provided for perceptual judgment. The results showed that, under the three noise conditions, the average perceptual accuracies of the three communicative functions were 80.66% and 38% for the control group and the heroin addicts, respectively. Significant differences were found in the perception of the three communicative functions between the control group and the heroin addicts under the three noise conditions, except for the recognition of imperative under strong noise condition (i.e., SNR = 0). Moreover, heroin addicts showed good accuracy (around 50%) in recognizing imperative and poor accuracy (i.e., lower than the chance level) in recognizing interrogative. This paper not only fills the research gap in the perception of communicative functions in Mandarin speech among drug addicts but also enhances the understanding of the effects of drugs on speech perception and provides a foundation for the speech rehabilitation of drug addicts.

Analytical characterization and differentiation between threo- and erythro-4-fluoroethylphenidate

PURPOSE

Methylphenidate analogs appeared on the drug market during the last years. Its analogs contain two chiral centers and, thus, have potential varying configurations (i.e., threo and erythro forms). This study presents the analytical characterization of 4-fluoroethylphenidate (4-FEP) and its differentiation between threo- and erythro-4-FEP.

METHODS

Analysis of the samples included high-performance liquid chromatography (HPLC), gas chromatography-electron ionization-mass spectrometry (GC-EI-MS), high-resolution mass spectrometry (HRMS) analyses, nuclear magnetic resonance (NMR) spectroscopy and X-ray crystal structure analysis.

RESULTS

NMR spectroscopic investigations confirmed the differences between threo- and erythro-4-FEP, and demonstrated that both isomers could be separated using HPLC and GC methods. Two samples obtained from one vendor in 2019 consisted of threo-4-FEP, whereas the other two samples obtained from a different vendor in 2020 consisted of a mixture of threo- and erythro-4-FEP.

CONCLUSIONS

Several analytical approaches including HPLC, GC-EI-MS, HRMS analyses, NMR spectroscopy and X-ray crystal structure analysis enabled the unambiguous identification of threo- and erythro-4-FEP. The analytical data presented in this article will be useful for identifying threo- and erythro-4-FEP included in illicit products.

Better characterization of attention and hyperactivity/impulsivity in children with ADHD: The key to understanding the underlying white matter microstructure

The apparent increase in the prevalence of the attention deficit hyperactivity disorder (ADHD) diagnosis raises many questions regarding the variability of the subjective diagnostic method. This comprehensive review reports findings in studies assessing white matter (WM) bundles in diffusion MRI and symptom severity in children with ADHD. These studies suggested the involvement of the connections between the frontal, parietal, and basal ganglia regions. This review discusses the limitations surrounding diffusion tensor imaging (DTI) and suggests novel imaging techniques allowing for a more reliable representation of the underlying biology. We propose a more inclusive approach to studying ADHD that includes known endophenotypes within the ADHD diagnosis. Aligned with the Research Domain Criteria Initiative, we also propose to investigate attentional capabilities and impulsive behaviours outside of the borders of the diagnosis. We support the existing hypothesis that ADHD originates from a developmental error and propose that it could lead to an accumulation in time of abnormalities in WM microstructure and pathways. Finally, state-of-the-art diffusion processing and novel artificial intelligence approaches would be beneficial to fully understand the pathophysiology of ADHD.

Pathophysiology and Current Drug Treatments for Post-Stroke Depression: A Review

Post-stroke depression (PSD) is a biopsychosocial disorder that affects individuals who have suffered a stroke at any point. PSD has a 20 to 60 percent reported prevalence among stroke survivors. Its effects are usually adverse, can lead to disability, and may increase mortality if not managed or treated early. PSD is linked to several other medical conditions, including anxiety, hyper-locomotor activity, and poor functional recovery. Despite significant awareness of its adverse impacts, understanding the pathogenesis of PSD has proved challenging. The exact pathophysiology of PSD is unknown, yet its complexity has been definitively shown, involving mechanisms such as dysfunction of monoamine, the glutamatergic systems, the gut-brain axis, and neuroinflammation. The current effectiveness of PSD treatment is about 30-40 percent of all cases. In this review, we examined different pathophysiological mechanisms and current pharmacological and non-pharmacological approaches for the treatment of PSD.

The effects of psychostimulants on cognitive functions in individuals with attention-deficit hyperactivity disorder: A systematic review

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is associated with a broad range of deficits in cognitive functions which has significant implications for quality of life. Psychostimulants are demonstrated to improve symptoms of inattention and hyperactivity/impulsivity, however, their impact on cognition remains incompletely characterized. Herein, the aim of this systematic review is to synthesize the extant literature reporting on the effects of psychostimulants on cognitive function in individuals with ADHD.

METHOD

A systematic search of PubMed, Scopus, and Web of Science from inception to July 2021 was conducted. Additional studies were identified through Google Scholar and a manual search of the reference lists of relevant articles. Inclusion criteria were original studies that evaluated the cognitive function of individuals with ADHD taking psychostimulants drugs. We assessed the quality of the included papers using the Newcastle-Ottawa scale (NOS).

RESULTS

A total of 10 studies involving 753 subjects with ADHD and 194 healthy controls were identified and eligible for inclusion. Nine studies evaluated the impact of methylphenidate on cognitive function and one study investigated the use of lisdexamfetamine. Results indicated that attentional deficits such as memory, vigilance, divided attention, phasic and tonic alertness, and focused attention were improved in ADHD patients treated with psychostimulants. The efficacy of psychostimulants in improving other domains of cognition remains inconclusive due to conflicting evidence or insignificant findings (ie. academic performance and executive function). Overall, results indicate that psychostimulants may improve only select domains of cognition (ie. memory and attention).

CONCLUSION

Psychostimulants are reported to improve several disparate aspects of cognition among individuals with ADHD. Further research is needed to better understand the complex relationships between cognition and behavior in ADHD, as well as the impact of medication on these distinct aspects of functioning. Further research is also needed to determine whether the pro-cognitive effect of stimulants would be transferable to other mental disorders.

Students' use of caffeine, alcohol, dietary supplements, and illegal substances for improving academic performance in a New Zealand university

This study aimed to describe patterns of use and attitudes towards a broad variety of substances for improving academic performance at a New Zealand university. 685 students (from 1800 invited) completed an online questionnaire (38% response rate). They were asked about their lifetime and current substance use for improving academic performance, as well as their reasons for use, attitudes and perceptions of: caffeine, alcohol, dietary supplements, prescription stimulants, other prescription substances, and illicit substances. 80% (95% CI: 76.3, 82.5) reported ever using any substance to help improve academic performance, mainly to stay awake and improve concentration. Caffeine (70%, 95% CI: 66.3, 73.3) and dietary supplements (32%, 95% CI: 28.3, 35.5) were most commonly used. 4% (95% CI: 2.7, 5.9) reported use of prescription stimulants, mostly methylphenidate, and another 4% (95% CI: 2.7, 5.9) reported using illicit substances for improving academic performance. Users of prescription stimulants were more likely than non-users to believe that they were safe, morally acceptable, and that they should be available legally for enhancing academic performance. We close with discussions on broadening the focus of substances for improving academic performance in public health debates. Further qualitative research from small countries is also needed to move towards a place-based approach for clarifying ethical implications, inform policy in universities, and understand how injustices are created through the use of and ability to purchase different substances.

Is Methylphenidate Beneficial and Safe in Pharmacological Cognitive Enhancement?

Nootropics are drugs used to either treat or benefit cognition deficits. Among this class, methylphenidate is a popular agent, which acts through indirect dopaminergic and noradrenergic agonism and, therefore, is proposed to enhance performance in catecholamine-dependent cognitive domains such as attention, memory and prefrontal cortex-dependent executive functions. However, investigation into the efficacy of methylphenidate as a cognitive enhancer has yielded variable results across all domains, leading to debate within the scientific community surrounding its off-label use in healthy individuals seeking scholaristic benefit or increased productivity. Through analysis of experimental data and methodological evaluation, it is apparent that there are dose-, task- and domain-dependent considerations surrounding the use of methylphenidate in healthy individuals, whereby tailored dose administration is likely to provide benefit on an individual basis dependent on the domain of cognition in which benefit is required. Additionally, it is apparent that there are subjective effects of methylphenidate, which may increase user productivity irrespective of cognitive benefit. Whilst there is not extensive study in healthy older adults, it is plausible that there are dose-dependent benefits to methylphenidate in older adults in selective cognitive domains that might improve quality of life and reduce fall risk. Methylphenidate appears to produce dose-dependent benefits to individuals with attention-deficit/hyperactivity disorder, but the evidence for benefit in Parkinson's disease and schizophrenia is inconclusive. As with any off-label use of pharmacological agents, and especially regarding drugs with neuromodulatory effects, there are inherent safety concerns; epidemiological and experimental evidence suggests there are sympathomimetic, cardiovascular and addictive considerations, which might further restrict their use within certain demographics.

Association between amphetamine-related disorders and dementia-a nationwide cohort study in Taiwan

Objective

We have conducted a study to clarify the association between amphetamine‐related disorders (ARD) and the risk of developing dementia.

Methods

This study used a retrospective cohort design by using Taiwan’s National Health Research Institute Database. A random sample of 68,300 subjects between January 1, 2000, and December 31, 2015, was obtained, comprising of 17,075 patients with ARD, and 51,225 controls without ARD (1:3), matched for gender and age group. After adjusting for covariates, a Fine and Gray’s survival analysis (competing with mortality) was used to compare the risk of dementia during a 15‐year follow‐up period.

Results

In the present study, 1,751 of 17,075 patients with ARD and 2,147 of 51,225 in the control group without ARD (883.10 vs 342.83 per 100,000 person‐years) developed dementia. ARD cohort was more likely to develop dementia (hazard ratio = 4.936 [95% CI: 4.609–5.285, P < 0.001). After adjusting for gender, age groups, education, monthly insured premiums, urbanization level, geographic region, comorbidities, the hazard ratio for ARD patients was 5.034 (95% CI: 4.701–5.391, P < 0.001). ARD has been associated with overall dementia, Alzheimer dementia, vascular dementia, and other dementia. Both the amphetamine use disorder and amphetamine‐induced psychotic disorders were associated with the risk of overall dementia, Alzheimer dementia, vascular dementia, and other dementia.

Interpretation

This study shows that patients with ARD, both the amphetamine use disorder and the amphetamine‐induced psychotic disorder, may have a nearly fivefold risk of developing dementia, including Alzheimer dementia and other types of dementia.

Neurophysiological and Neurochemical Effects of the Putative Cognitive Enhancer (S)-CE-123 on Mesocorticolimbic Dopamine System

Treatments for cognitive impairments associated with neuropsychiatric disorders, such as attention deficit hyperactivity disorder or narcolepsy, aim at modulating extracellular dopamine levels in the brain. CE-123 (5-((benzhydrylsulfinyl)methyl) thiazole) is a novel modafinil analog with improved specificity and efficacy for dopamine transporter inhibition that improves cognitive and motivational processes in experimental animals. We studied the neuropharmacological and behavioral effects of the S-enantiomer of CE-123 ((S)-CE-123) and R-modafinil in cognitive- and reward-related brain areas of adult male rats. In vivo single unit recordings in anesthetized animals showed that (S)-CE-123, but not R-modafinil, dose-dependently (1.25 to 10 mg/kg i.v.) reduced firing of pyramidal neurons in the infralimbic/prelimbic (IL/PrL) cortex. Neither compound the affected firing activity of ventral tegmental area dopamine cells. In freely moving animals, (S)-CE-123 (10 mg/kg i.p.) increased extracellular dopamine levels in the IL/PrL, with different patterns when compared to R-modafinil (10 mg/kg i.p.); in the nucleus accumbens shell, a low and transitory increase of dopamine was observed only after (S)-CE-123. Neither (S)-CE-123 nor R-modafinil initiated the emission of 50-kHz ultrasonic vocalizations, a behavioral marker of positive affect and drug-mediated reward. Our data support previous reports of the procognitive effects of (S)-CE-123, and show a minor impact on reward-related dopaminergic areas.

Brief and extended abstinence from chronic oral methylphenidate treatment produces reversible behavioral and physiological effects

Methylphenidate (MP) is a commonly prescribed psychostimulant to individuals with Attention Deficit Hyperactivity Disorder, and is often used illicitly among healthy individuals with intermittent breaks to coincide with breaks from school. This study examined how intermittent abstinence periods impact the physiological and behavioral effects of chronic oral MP self-administration in rats, and whether these effects persist following prolonged abstinence from the drug. Rats were treated orally with water, low-dose (LD), or high-dose (HD) MP, beginning at PND 28. This daily access continued for three consecutive weeks followed by a 1-week abstinence; after three repeats of this cycle, there was a 5-week abstinence period. Throughout the study, we examined body weight, food intake, locomotor activity, and anxiety- and depressive-like behaviors. During the treatment phase, HD MP decreased body weight, food intake, and depressive- and anxiety-like behaviors, while it increased locomotor activity. During intermittent abstinence, the effects of MP on locomotor activity were eliminated. During prolonged abstinence, most of the effects of HD MP were ameliorated to control levels, with the exception of weight loss and anxiolytic effects. These findings suggest that intermittent exposure to chronic MP causes physiological and behavioral effects that are mostly reversible following prolonged abstinence.

Pharmacological Human Enhancement: An Overview of the Looming Bioethical and Regulatory Challenges

Cognitive enhancement, a rather broad-ranging principle, can be achieved in various ways: healthy eating and consistent physical exercise can lead to long-term improvements in many cognitive domains; commonplace stimulants such as caffeine, on the other hand, temporarily raise levels of alertness, attentiveness, and concentration; sedative substances are also used as an indirect form of enhancement to relax before an exam or an important meeting. Such approaches raise no ethical issue. Nonetheless, clinical research has led to the off-label use of drugs called nootropics or "smart drugs", which can, under certain conditions, elicit some degree of cognition-improving effects: methylphenidate and modafinil can enhance working memory and concentration in healthy individuals, although the significance and effectiveness of such applications are dubious. Such "cognitive enhancement" methods, however, do raise multiple ethical issues, and their contentious nature has caused bioethical authorities to lay out opinions and recommendations meant to regulate their use. Most notably, the Italian Committee on Bioethics has extensively dealt with the spread of nootropics, which resulted in the Italian Code of Medical Ethics including "cognitive enhancement" drugs and their prescription by doctors as critical points, along with cosmetic surgery (the latest version of the Code, updated in December 2017, deals with the two separately, in Article 76 and 76 BIS). The United States Presidential Commission for the Study of Bioethical Issues broadened the scope of cognitive enhancement techniques so as to include neural modifiers, i.e. mechanisms of brain and nervous system change: a much wider array of interventions, technologies, behaviors, and environmental conditions that may potentially affect several aspects of the human brain and nervous system. The potential of neuroscience to profoundly reshape society is nothing short of mind-blowing.

Amphetamine exposure and dementia - A hypothesis of the long term sequelae of cognitive enhancers based on opponent process theory

Dementia is a cluster of brain dysfunctions with a characteristic of progressively debilitating in individuals' ability of operating cognitive functions and that affects seriously to patients' daily life. We presented a hypothesis in this article that earlier exposure of a common used cognitive enhancer amphetamine may lead to individuals to be more liable to develop dementia in their later life based on the opponent process theory. The theory proposes that following a positive response, homeostatic changes in brain circuits may function to go opposite to the positive response, thus a cognitive deterioration may incur in later life in the individuals who exposed to amphetamine earlier. Along with the hypothesis, amphetamine is also highly associated with the working hypothesis updated for dementia in terms of beta-amyloid cascade, tau protein, oxidative stress and neural inflammation. Finally, we presented two practical methods to evaluate the hypothesis. In non-human approach, rat model of amphetamine dependence would be employed together with evaluations of behavioral performance of memory test and neurochemical markers associated with oxidative stress. In human approach, a matched-cohort design observational study would be highly recommended.

Repeated Use of the Psychoactive Substance Ethylphenidate Impacts Neurochemistry and Reward Learning in Adolescent Male and Female Mice

Schedule II prescription psychostimulants, such as methylphenidate (MPH), can be misused as nootropic drugs, i.e., drugs that enhance focus and cognition. When users are unable to obtain these prescribed medications, they may seek out novel psychoactive substances (NPSs) that are not yet scheduled. An example of a NPS reportedly being abused is ethylphenidate (EPH), a close analog of MPH but with a higher preference for the dopamine transporter compared with the norepinephrine transporter. Therefore, based upon this pharmacological profile and user self-reports, we hypothesized that repeated EPH exposure in adolescent mice may be rewarding and alter cognition. Here, we report that repeated exposure to 15 mg/kg EPH decreased spatial cognitive performance as assessed by the Barnes maze spatial learning task in adolescent male C57Bl/6 mice; however, male mice did not show alterations in the expression of mature BDNF - a protein associated with increased cognitive function - in key brain regions. Acute EPH exposure induced hyperlocomotion at a high dose (15 mg/kg, i.p.), but not a low dose (5 mg/kg, i.p.). Interestingly, mice exhibited significant conditioned place preference at the low EPH dose, suggesting that even non-stimulating doses of EPH are rewarding. In both males and females, repeated EPH exposure increased expression of deltaFosB - a marker associated with increased risk of drug abuse - in the dorsal striatum, nucleus accumbens, and prefrontal cortex. Overall, our results suggest that repeated EPH use in adolescence is psychostimulatory, rewarding, increases crucial brain markers of reward-related behaviors, and may negatively impact spatial performance.