The study suggests it has no negative affect on performance, however it has been found to be an effective aid for insomnia:
23 Hispanic men and women were used as participants for study on valerian and insomnia. Eleven of which were diagnosed with major depression, they were all instructed to take one valerian capsule each night. At the end of 2 weeks, most patients described the medication as extremely helpful and would consider purchase (Domniquez et al, 1994).
‘The placebo effect is the measurable, observable, or felt improvement in health not attributable to treatment’ i.e. a ‘fake’ pill, usually a sugar or a starch pill, is given as a prescribed treatment. The effect is believed to be psychological, because of belief in the treatment held by the patient. Kirsch (1999) suggested that the effectiveness of drugs such as Prozac could be explained in terms of the placebo effect. He analysed 19 clinical trials of anti depressants and found that ‘expectation of improvement, not adjustments to brain chemistry accounted for 75 % of the drugs’. It has also been argued that positive beliefs about treatments may have a significant biochemical effect: sensory experience and positive thoughts can affect neurochemistry in another interesting study, of asthmatics, researcher s found they could produce dilation of the airways by simply telling people they were inhaling a bronchiodilater, even when they were not.
It is evident there is little research into the effects of stimulants and depressants on an individuals cognitive performance, as mentioned both stimulants and depressants have supposed effects on the CNS and brain, however there is little research on its effects on cognitive motor performance. In a similar study to the kuhlman et al (1999), valerian, ginseng and a placebo will be used to study whether they have an effect on cognitive performance.
Method:
Design;
Between-groups experimental design was used, the independent variables were the 3 drugs: valerian, ginseng and placebo the scores obtained on the tasks carried out by the participants was the dependent variable. Type of drug was randomly allocated to each participant, however the participant was not aware of which of the three drugs they had taken. Consent was gained prior to the experiment from each participant and the nature of the study was explained.
Participants;
Participants were Coventry University students taking physiological psychology. Participants were instructed a week before to avoid consuming caffeine two hours prior to the study, as this confounding variable may affect the validity of the results.
Materials;
The substances used in this study were red Kooga Korean ginseng containing 75mg of standardised extract per tablet (Panax Ginseng C.A. Meyer) and Lichtwer Pharma Herbal Valerian containing 300mg of standardised LI 156 extract of Valerian (Valeriana officinalis radix) and Superdrug Vitamin C (200mg per tablet) was used as the placebo.
Procedure;
The purpose of the experiment was explained by experimenter after which consent forms were given out and the opportunity to withdraw was offered. Each participant who had given consent to sontinue with study was given a drug, either Ginseng , Valerian or placebo. Each of the control group was not aware of what they had taken, they were simply given a number to remember whilst they carried out the tasks, this was for the benefit of the experimenter to determine which drug had been given after the study, furthermore the participants did not know what their fellow participants had taken and carried out the tasks simultaneously.
The first task was a continuous performance task, which was completed on the computer. Participants viewed 15 different images for for 15 minutes which appered repeatedly one at a time on the computer screen. The images were presented in a random manner and the time between presentations of each image also differed.
The second task was a measure of reaction time, performed on a computer. Participants were instructed to press the space bar as quickly as possible when 0 appeared on the computer screen. Response time was measured from when the 0 appeared till the moment the key is pressed.
The third task was an immediate recall test, participants were shown 15 words. Each word was presented for 5 seconds. A ten second gap was measured after presentation of the list. Finally participants were given two minutes to recall as many words as they could from the list.
The final test was the positive and negative affect schedule (Panas) (Watson, Clark and Tellegen 1988). The scale is a measure of feelings and emotions and consists of numerous words which describe this. Participants were asked to read each item and then mark the appropriate answer in the space next to that word, indicating to what extent they felt at the time. The following scale was given to record each individual’s answers. (1= very slightly or not at all, 2= a little, 3= moderately, 4= quite a bit, 5=extremely).
After completion of all the tasks, participants were asked to reveal what drug they thought they had taken. Results of each task and what they thought they had taken was recorded.
Results:
In order to analyse the results the Kruskal-Wallis test was used, as this is the non-parametric equivalent to a one-way ANOVA. Initial inspection of the dependent variables showed that the data were significantly skewed and that there was a lack of homogeneity of variance between the experimental groups. As the data failed to satisfy the assumptions required for parametric analyses, non-parametric analyses were conducted.
Having used the Kruskal-Wallis test the results show that both simple reaction time and the CPT are significant.
Table 1: results showing the significance of scores for each test.
For the simple reaction test the Mean = 0.43 and SD = .049
For the CPT Mean = 18.52 and SD = 7.96.
Table 1. above shows Simple reaction time was significant as it had a value of p = .016 as was CPT which had a value of p = .014.
Whilst the Kruskal-Wallis test identifies that the two test scores are significant it does not tell us which drug is responsible for this. Therefore we have also used the Mann Whitney test to compare the groups of drugs against each other in turn to discover which drug had an effect on performance.
Ginseng was compared with valerian and the results (in table 2) showed that both simple reaction time and CPT were of significance. Simple reaction time p = .004 and CPT p = .007.
Table 2 shows valerian compared with Ginseng
a Grouping Variable: Experimental group
Again this result does not identify which drug is having an effect.
Ginseng was compared with placebo (Table 3) and the results here showed that none of the tests were significantly affected.
Table 3 shows Ginseng compared with placebo
a Grouping Variable: Experimental group
Finally placebo was compared with valerian, (table 4) the results here showed that CPT was significant. CPT p = .018.
Table 4 shows valerian compared with placebo
a Grouping Variable: Experimental group
The comparison of drugs made by the Mann Whitney test has analyzed the drugs; from this we can draw the conclusion that valerian is the drug, which has affected motor performance in this study. The tables above support this argument showing that each time valerian is compared to the other drugs the results show significance.
The graph (figure 1) below illustrates that valerian has a positive reaction on participants in the study as more errors are made during the CPT test. The participants who had taken valerian prior to the experiment have made extensively more errors than those under the influence of ginseng and placebo.
Figure 1: A graph showing the amount of errors made by participants under the influence of the three drugs ginseng placebo and valerian.
Discussion:
As evident from the results Ginseng and the placebo did not seem to have an effect on cognitive performance, however it was not the case for Valerian which did impair cognitive performance as hypothesised by previous studies.
The decrease in performance for Valerian can be attributed to its essential oils which contain monoterpenes and sesquiterpenes; these contain hydroxyvalernic acid and acetoxyvalerenic acid that can inhibit the breakdown of GABA. GABA is known to decrease brain activity and thus if the breakdown is inhibited a surplus of GABA is present to decrease brain activity and consequently participants which took valerian performed less well on the tasks. The results however seem to contradict the findings of the Kuhlman et al (1999) study in which they found that valerian did not seem to have a significant effect on reaction time, alertness or concentration.
The most frequent use of Valerian is for the relief of insomnia, so whilst it may help in restoring sleep perhaps its effects remain. Several studies have supported its effectiveness as a sedative, and this can also be related to low performance on the tasks. Wheatley et al (2001) treated stress induced insomnia with the herb Kava and Valerian. Participants suffering from stress-induced insomnia were given Kava for 6 weeks and another group was given valerian for 6 weeks and after a wash out period of 2weeks given combined treatment of Kava and Valerian. Stress was measured in three areas: social, personal, and life events and same for insomnia: time to fall asleep, hours slept and waking mood. It was found that both compounds significantly relieved stress individually, with no significant differences between them. These findings are in line with several other studies that support its effectiveness as a sedative.
The non-effect of Ginseng could be attributed to numerous factors; research has shown that ginseng requires a period of time before its effects are evident.
The tasks in this study were carried out immediately after taking Ginseng, D’Angelo et al., (1986) however examined the effects of 12 weeks daily administration of ginseng. Tests included those assessing motor performance, speed of performance on attentional tasks, mental arithmetic and logical reasoning. The result showed that performance was significantly improved for the Ginseng group in comparison to placebo, however only on the mental arithmetic test; hence it may be the case that it did not have enough time to work.
Another problem could be concerning dosage, Kennedy et al (2000) found that improvement in performance was dosage dependant. They found that 4000mg of Ginseng had a lasting improvement on cognitive performance whereas both 200mg and 600mg slowed down performance of attentional tasks. It is possible that the dosage was too little to actually have an affect.
Experimental bias could also have had an effect: The majority of the participants assumed they were taking the placebo despite what they were actually taking and may have acted in a way as to support that. I.e. they may have acted in a neutral manner, not too stimulated or too sedated, acted in a unaffected way because the placebo is ‘fake’ and has no effects.
There are a number of limitations with this study; firstly cognitive tasks were presented immediately after taking each particular drug, however as aforementioned research has shown that it may take time for drugs such as ginseng to have it effects, and perhaps there was insufficient time for this to happen. Secondly individual differences were another problem, participants individual competence in each task was not taken into account. Perhaps it would have been better to test them before and after taking each drug, and thus allow comparisons to be made on whether it actually had effects on cognitive performance and finally perhaps it would have been a better idea to analyse the effects of each drug using the same participant, with 3-4 day wash off time period before next drug, this would largely eliminate any effects of individual differences and provide a more accurate account of the effects of each drug on cognitive performance.
References:
Gazzaniga, M. S. (2000). Cognitive Neuroscience: A Reader. Oxford. Blackwell.
Julien, R. M. (2001). A Primer of Drug Action. London. W. H. Freeman.
Strange, P. G. (1992). Brain Biochemistry and Brain Disorders. Oxford. OUP.
, ; Military Psychology, Vol. 4, 1992
; American Psychiatric Press, 1994
Journal article Roy W. Kanne, Human Factors, Vol. 43, (2001)
The Influence of Stimulants, Sedatives, and Fatigue on Tunnel Vision: Risk Factors for Driving and Piloting.
