Effects of Caffeine Use

Loke, W. and Meliska, C., Effects of caffeine use and ingestion on a protracted vigilance test. Psychopharmacology 87, 344-350, 1984. 

In healthy boys, there were increases in subjective anxiety in long-term low-caffeine users, and withdrawal symptoms in high-caffeine users. No beneficial effects of caffeine use were found (37). It has been recommended that children should take caffeine only in analgesic products and in a dose related to their age (SEDA-5, 6). 

Acute Toxic Effects of Caffeine Chronic Effects of Caffeine Use Therapeutic Uses of Caffeine Conclusions Summary... 

Caffeine is an extremely important drug because of its widespread use. Overall it also seems to be a relatively safe drug. Despite the many years of research that have been devoted to caffeine, however, we still have a lot to learn about it. Probably the most essential research concerns tfcveloping better ways to obtain accurate measures of caffeine consumption. Such advances would help us answer important research questions. F or example, we need to know more about the long-term effects of caffeine use in children, the development of tolerance to caffeine, and the prevalence of more minor symptoms of higher, but not extreme, levels of caffeine use. Another question is how caffeine affects people in special populations, such as those who arc medically or psychiatrically ill. 

Due to the CNS stimulant effects of caffeine, use of caffeine-containing products is cautioned in persons with heart disorders, as excessive caffeine consumption may increase heart rate or exacerbate arrhythmias or psychological disorders, as caffeine may aggravate depression or induce anxiety (Brinker 2001). 

The bronchodilating effect of caffeine has been recognized for hundreds of years. In the western world the first description of a caffeine preparation for asthma was made in 1859 (59) by a Scottish physician who recommended strong black coffee as a bronchodilator. In many parts of the world, however, use of xanthines is less frequent than in the United States. 

In addition to coffee and tea, the psychological effects of caffeine can be obtained from a number of other food sources. Chocolate is a popular and widely consumed source, but the drug is also found in considerable quantities in a number of medications, both prescription and over-the-counter (OTC). Caffeine tablets (e.g., No-Doz) are sold for those who use the drug to study, drive, or engage in other activities. Less obvious is the caffeine content in analgesics, cold preparations, and anorectants. 

Interestingly enough, most of the studies reporting positive effects of caffeine in information-processing tasks have used primarily or exclusively male subjects.39 42 43 45 48 59 In fact the only study that found positive cognitive effects of caffeine on females employed fatigued females, whose baseline arousal levels may have been lower.41... 

James, J. and Stirling, K., Caffeine A survey of some of the known and suspected deleterious effects of habitual use. British Journal of Addiction 78(3), 251-258. 

The failure to find an effect in the American trial above was confirmed in a study conducted in the Netherlands, which also used paper-filtered, drip-brewed coffee.14 In that 12-week experiment, 23 women and 22 men who habitually drank 4 to 6 cups of coffee per day were assigned to consume 5 cups/day of either caffeinated (417.5 mg caffeine/day) or decaffeinated coffee (15.5 mg caffeine/day) for six weeks, and then switch for another six weeks. The blend of coffee beans was 71% Arabica and 29% Robusta for the caffeinated coffee, and 58% Arabica and 42% Robusta for the decaffeinated coffee. Lipid values at the end of both six-week study periods were almost identical. Total cholesterol was 5.47 vs. 5.48 mmol/ L (212 vs. 212 mg/dL), LDL-C was 3.41 vs. 3.40 mmol/L (132 vs. 131 mg/ dL), HDL-C was 1.52 vs. 1.52 mmol/L (59 vs. 59 mg/dL), and TG were 1.17 vs. 1.20 mmol/L (104 vs. 106 mg/dL) for the caffeinated vs decaffeinated coffee periods, respectively. Further, a small study of 12 Finnish men also failed to find an effect of caffeinated coffee on serum cholesterol levels.15 However, the study period was only three weeks which may have been insufficient. 

Before discussing the animal data it is important to note that caffeine is metabolized differently in experimental animals than it is in humans. This is particularly so in the rat, which is the most common experimental model used. Therefore results in animals, either positive or negative, cannot be directly applied to humans. However, since caffeine itself and some of its metabolites are present in both the animal experiments and during human exposure, an adverse effect of caffeine in an animal model should be verified or excluded in the human. 

A frequently used test to assess the effect of psychostimulants is the CPT. Methylphenidate at doses of around 0.3mg/kg usually improves performance, Le. reduces the number of errors, on the CPT whereas the effects of d-amphetamine (at doses between 5 and 20 mg) and pemoline (10 60mg) appear to be less reliable (Riccio et al., 2001). The stimulating effect of caffeine in various areas of performance is of shorter duration than that of... 

Most follow-ups to earlier studies warning of the adverse effects of caffeine have failed to duplicate the initial findings, especially for the moderate use of caffeine. However, at the start of the new millennium, youth culture thrived on the excessive use of caffeine. New drinks were purposely formulated to contain large amounts of the mild stimulant, increasing the risk of possible adverse effects. 

Different lines of treatment for sleep disorders associated with EDS, such as continuous positive airway pressure or airway surgery, were evaluated using the MSLT. In comparing pre- and posttreatment symptoms, a subject may perceive an improvement of awareness as very substantial, whereas the MSLT may reveal that the vulnerability remains. Hence, objective assessment of the response is offered by the MSLT (16,54). The alerting effect of caffeine has been proven by its ability to increase the sleep latency on the MSLT of normal sleep-deprived subjects (55). 

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