Plant-derived nootropics and human cognition: A systematic review

Substances with modulatory capabilities on certain aspects of human cognition have been revered as nootropics from the dawn of time. The plant kingdom provides most of the currently available nootropics of natural origin. Here, in this systematic review, we aim to provide state-of-the-art information regarding proven and unproven effects of plant-derived nootropics (PDNs) on human cognition in conditions of health and disease. Six independent searches, one for each neurocognitive domain (NCD), were performed in parallel using three independent scientific library databases: PubMed, Cochrane and Scopus. Only scientific studies and systematic reviews with humans published between January 2000 and November 2021 were reviewed, and 256 papers were included. Ginkgo biloba was the most relevant nootropic regarding perceptual and motor functions. Bacopa monnieri improves language, learning and memory. Withania somnifera (Ashwagandha) modulates anxiety and social-related cognitions. Caffeine enhances attention and executive functions. Together, the results from the compiled studies highlight the nootropic effects and the inconsistencies regarding PDNs that require further research.Supplemental data for this article is available online at https://doi.org/10.1080/10408398.2021.2021137.

A Systematic Review of the Use of St. John's Wort for Smoking Cessation in Adults

St. John's wort (SJW) has been researched and clinically used for treating various psychiatric disorders, including depression. Few clinical trials have studied its use in smoking cessation. This systematic review provides comprehensive evidence of the studies conducted to date. Five databases were searched for randomized controlled trials (RCTs) that evaluated the effectiveness of SJW for smoking cessation in adults. The trials included the use of SJW alone, or along with nicotine replacement therapy, chromium, or behavioral therapies. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were used to report this systematic review. Overall, four RCTs met the eligibility criteria, and the risk of bias analysis was conducted using the Cochrane criteria. Abstinence, along with other physical symptoms, were measured as outcomes at the end of the follow-up period. Studies reported variable abstinence rates and a decrease in cravings at the end of 12-14 weeks. However, there was minimal to no difference reported between the intervention and placebo groups in all of the clinical trials. One of the studies reported minimal physical side effects. Overall, SJW was well tolerated. Quality analysis of the included studies showed low concerns in two studies while the other two studies showed high concerns in the risk of bias judgment. More clinical trials with larger sample sizes should be conducted in the future to evaluate the effectiveness of the use of SJW for smoking cessation.

Subchronic treatment with St John's wort produces a positive shift in emotional processing in healthy volunteers

BACKGROUND

The neurocognitive model of antidepressant treatment in depression states that antidepressants work by producing relatively immediate positive shifts in emotional processing, which translate into clinical improvement with time. St John's Wort has shown antidepressant potential in randomised controlled trials; however, its pharmacological actions are broad and it is unknown whether treatment also produces changes in emotional processing.

AIMS

We investigated whether short-term treatment with St John's wort has similar effects on emotional processing to those reported with other antidepressants such as selective serotonergic reuptake inhibitors.

METHODS

Forty-eight healthy participants were given St John's wort or placebo treatment for seven days. On day 7 they completed a battery of tasks to measure emotional processing and other elements of cognition.

RESULTS

St John's wort treatment produced similar changes to other antidepressants, for example reducing recognition of disgusted faces and attention to fearful faces, while increasing memory for positive words. We failed to find evidence for an effect of St John's wort on other aspects of cognition including working memory.

CONCLUSIONS

These findings lend support to the theory that the production of early positive biases in emotional processing may be a common feature of all clinically effective antidepressants with diverse pharmacological mechanisms.

Different physiological and behavioural effects of e-cigarette vapour and cigarette smoke in mice

Nicotine is the primary addictive substance in tobacco smoke and electronic cigarette (e-cig) vapour. Methodological limitations have made it difficult to compare the role of the nicotine and non-nicotine constituents of tobacco smoke. The aim of this study was to compare the effects of traditional cigarette smoke and e-cig vapour containing the same amount of nicotine in male BALB/c mice exposed to the smoke of 21 cigarettes or e-cig vapour containing 16.8 mg of nicotine delivered by means of a mechanical ventilator for three 30-min sessions/day for seven weeks. One hour after the last session, half of the animals were sacrificed for neurochemical analysis, and the others underwent mecamylamine-precipitated or spontaneous withdrawal for the purposes of behavioural analysis. Chronic intermittent non-contingent, second-hand exposure to cigarette smoke or e-cig vapour led to similar brain cotinine and nicotine levels, similar urine cotinine levels and the similar up-regulation of α4β2 nicotinic acetylcholine receptors in different brain areas, but had different effects on body weight, food intake, and the signs of mecamylamine-precipitated and spontaneous withdrawal episodic memory and emotional responses. The findings of this study demonstrate for the first time that e-cig vapour induces addiction-related neurochemical, physiological and behavioural alterations. The fact that inhaled cigarette smoke and e-cig vapour have partially different dependence-related effects indicates that compounds other than nicotine contribute to tobacco dependence.