Effects Of Stress On Cortisol Level And Memory Retrieval In Healthy Young Students

Your task is to write a laboratory report on the study. Your lab report must be written using APA standard and format conventions. Thus, you should consult Burton et al. (2018) or O’Shea’s Writing in Psychology texts when writing your lab report. Refer to the Unit Guide for further information and assessment details on the lab report.

To write a coherent lab report, you should:

1. Read the literature on the topic widely to build a strong rationale for the study, and make sure that your research question(s) and hypotheses are derived from existing literature and evidence
2. Discuss the findings in relation to the literature
3. Recognise strengths but focus on discussing weaknesses and making appropriate recommendation(s) to address any limitation.

Previous studies on effects of stress on cognitive function

Connotation of Stress on Cortisol and Memory Retrieval in Healthy Young Students

In this study the researcher was interested in the effects of stress on cognitive function, focusing especially on memory performance. Previous literature has shown that prolonged tension in humans can have high cortisol levels by activating the “hypothalamic–pituitary–adrenal” (HPA) axis (Aguilera, 2011). Gupta, & Morley (2011) emphasised on the adverse impact of HPA axis on cognitive insufficiencies, depression, and age related disease such as Alzheimer's. High levels of cortisol damage the nerves of the hippocampus, which triggers weakened memory performance. Huang et al. (2009) experimented with Alzheimer's patients to reveal the adverse impact of cortisol level on hippocampal volume and cognitive abilities. Most of the studies focused on the effects of stress on memory, and was less important in testing healthy people. In an experimental study, Schoofs, Wolf, & Smeet (2009) studied the impact of stress on working memory with health young men. In addition, majority of the studies with healthy people evaluated the experimental psychological effects in the observed stress memory, ignoring the impact of self-reported stress level (Jha, Stanley, Kiyonaga, Wong, & Gelfand, 2010). To narrow down this literary gap, the current study can be seen to investigate the effects of self-reported or tribulation stress on students ' memories. Especially, the relation between salivary cortisol levels and stress was assessed (Hellhammer, Wüst, & Kudielka, 2009). Secondly, the impact of stress on the memory performance of the students was also analysed.

The primary objective of the present study was to evaluate the stress/memory relationships to develop strategies to reduce the stress levels of the student population and possibly improve their academic performance. The DASS-21 scale has been utilized to assess the self-reported stress level by the participants (Gomez, 2016). The study hypothesises that there exists a positive linear relation between cortisol and stress levels. Secondly, it was also hypothesized that the relation between stress and memory scores was linear and negative.

Approval from the University Ethics Committee for Human Research was obtained by the researcher before the trial began. The study included 196 healthy young undergraduate psychology students (Male = 77, Female = 119) aged between 18 to 46 years (M = 27.63, SD = 6.17). None of the students suffered from medical or mental illness, and did not take any medications.

Presence of anxiety, stress and depression of participants were collected using a limited format of Depression, Anxiety, and Stress Scale (DASS21), which is a self-reported questionnaire developed by Gomez (2016), a consultant clinical psychologist. Participant’s symptoms over the last week were collected in a 0-3 scale. The short form DASS 21 is the shorter version of DASS 42 scale with 21 items. Depression, anxiety, and stress scores are separately collected by adding up scores from normal, mild, moderate, severe, and extremely severe items.

Purpose of this study

Medical condition assessment was done using “saliva sampling” and “cortisol” evaluation (Kuhlmann, & Wolf, 2005). Free cortisol levels were measured form the saliva collected. Subjects were asked to fill a small test tube with their saliva and then the tubes were labelled to avoid confusion.

Information about memory of participants was collected operating the Digit Span test by the “Wechsler Adult Intelligence Scale” (WAIS) (Benson, Hulac, & Kranzler, 2010). The subjects were made to listen to series of digits at a pace of 1 second per digit. Afterwards, participants recalled and wrote the series of numbers. This entire process was repeated in forward and backward sequence.

The experiment started on the first day at 10 A.M with complete explanation of the objective and procedure of the entire experiment to the participants. Participants were allowed time for providing their consent in lieu of the experiment. On receiving consent from the participants, saliva sample was collected using Salivette collection devices. Cortisol level was measured from the saliva of the participants using an immunoassay (Kuhlmann, Piel, & Wolf, 2005).

Stress level was estimated by presence of indicators in DASS 21 scale. Record of the symptoms over the previous week was completed for evaluating the stress score. The total scores of the stress components were later doubled for comparative analysis among depression, anxiety, and stress with percentile ranking for better understanding of severity of the emotional symptom.

Afterwards, digit span test was administered through voice reading of the forward and backward sequence of numbers. The participants were later asked to recall and write the digit sequence in the forward and backward arrangements. “Average memory score” was later evaluated from backward and forward digit span scores (Jasinski, Berry, Shandera, & Clark, 2011). All the participants received 2 hours of participation credit points in research work.

The cortisol levels was ranged between 5 nmol/L and 17 nmol/L, where the average cortisol level of the participants was evaluated at 10.04 Nano moles Per Litre (nmol/L) (SD = 3.10). The distribution was found to be slight right skewed, with median (Me = 9 nmol/L) being less than the average level. At 95% confidence level, average cortisol level of the students was predicted to be between 9.60nmol/L and 10.48nmol/L.

Stress levels of subjects evaluated using DASS 21 scale varied between 0 and 17, with an average score of 9.13 (SD = 5.08). Distribution of the stress levels was noted to be almost normal with very little negative skewness. Estimated average stress level of students’ at 95% level was noted to be between 8.42 and 9.85.

Methodology of the study

Descriptive summary of the Digit Span test revealed that “average memory score” for the sample participants ranged between 2.25 and 8.75 (M = 6.02, SD = 1.11). The distribution was almost normal with a slight positive skewness. Estimated mean of “average memory score” of the students at 95% level was between 5.71 and 6.02. The reliability coefficient of the digit span task was 0.83 (Wechsler, 1981).  

From the descriptive summary, probability distributions of the variables in the present study were noted to be almost normal with no major outliers. Linear and homoscedastic relations between the variables were assumed, and no separate measure of effect size evaluation in this work was carried out.

Linear relationship between stress score and cortisol level, as well as the linear relationship between stress score and memory score were measured using Pearson’s correlation coefficient. The correlation coefficient between stress score and cortisol level revealed a significantly positive and moderate linear association (r = 0.63, p < 0.01, 2-tailed). Similarly, the correlation coefficient between stress score and “average memory score” suggested a negative and weak linear association (r = -0.11, p = 0.14, 2-tailed), which was statistically not significant. The hypothesis assuming positive association between cortisol and stress levels was accepted. But on the contrary, there was not enough evidence to support the hypothesis that stress level and memory ability are significantly and negatively related.

Salivary cortisol successfully works as a marker of stress when controlled for sources of variance. Considering the complexities of evaluation methodology of stress level by self-reported questionnaire, unexpected or low covariance between stress level and cortisol level is not abnormal. But, the correlation results of the present study efficiently resembles with outcome of research by Hellhammer, Wüst, & Kudielka (2009). As expected, the said association was moderately high and significantly positive. In a study of relation between examination stress and self-reported stress, Murphy, Denis, Ward, & Tartar (2010) investigated undergraduate students. Their results showed that during examination cortisol concentration was higher compared to non-examination time. Hence, stress of examination was noted to significantly increase cortisol levels. The result of the present study was not under any exam like situation, but the positive correlation value indicates a parallel outcome. In another research by Vreeburg et al. (2010), relation between work-related stress and physical health of the participants was evaluated. Significantly high level of cortisol was found in employees working under enormous pressure with high stress. Although, the present work did not perform a comparative study with working pressure as special experimental situation, a positive linear relation between stress and cortisol level was still present.

Results of the study

Stress level has an adverse impact on spatial ability of children; especially sleep deprivation in young students significantly reduces cognitive enactment. Ahrberg, Dresler, Niedermaier, Steiger, & Genzel (2012) showed that correlation between academic performance and sleep quality was low but significantly positive, indicating low sleep quality with higher academic performance. The present study results of negative correlation between stress level and memory scores indicates decreasing memory capacity with increase in stress level, and are in line with the earlier study. Hinkelmann et al. (2009) worked on impact of cognitive deficiency on depression with 52 patients to show the relatively higher adverse impact of that cognitive deficiency on depression compared to healthy people. Hence, the adverse impact of stress on memory or cognitive ability has been established in earlier researches. The present results are in line with earlier works, but no comparative analysis was performed comparing healthy and depressed patients. De Veld, Riksen-Walraven, & de Weerth (2014) investigated impact of stress on working memory. They showed that working memory performance decreases with introduction of stress, and also emphasized on interaction and curvilinear effects while relating memory to physiology. The complexity of interaction and curvilinear impact was obviated in the current work to assess the linear relationship between stress and memory. Interestingly, relation between stress and memory was statistically insignificant in this lab work, indicating towards the existence of a non-linear relation. Hence, in future study interaction and curvilinear impact of stress on memory needs to be included in the scope of work. Owens, Stevenson, Hadwin, & Norgate (2012) worked with school children and showed that performance of working memory reduces in lieu of anxiety and depression. The academic performance of students decreases with increase in depression levels. The present sample consisted of young healthy subjects, but the results resembled with the said earlier research. Future study should test the results with a longitudinal study design.

Conclusion

In the present work young adults were considered in the sample to estimate the impact of stress on memory and cortisol levels. Previous research works showed that salivary cortisol levels are always higher in increased anxiety or depression. It was also noted that the relation between stress and cortisol levels are true irrespective of age and sample characteristics. In case of hypertension patients, the impact of stress on cortisol levels is much higher. Hence, the assumption of the study was noted to be comprehensively factual. Therefore, it can be inferred from the present results and previous literature that academic performance of students gets severely hampered by increased stress levels. Future study can be conducted with control group to estimate the impact of stress levels on academic performance.

Discussion of the results

The second finding of this work was the relation between stress and memory ability. The digit span test was used to measure the memory ability of the participants. Previous literature on this field indicates substantial work with working memory and stress components. A negative relation between memory ability and DASS 21 stress score was noted, but there was no significant evidence to establish the cogency of correlation. Hence, no noteworthy linear relation was found between stress and memory power, indicating towards presence of non-linear relation. Hence, the hypothesis assumed failed to get accepted in absence of enough statistical evidence.

The outcomes indicate that students should use mediator or practices like yoga to reduce stress levels in order to refute the adverse impact on working memory. This will help students in increasing academic performance.

References

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