This study was conducted with the second and third year of middle school students from a middle school in Daegu between 23rd May and 30th May Data was collected using a self-reported questionnaire from students. Of them, 9 students who either withdrew the consent or fail to complete psychological tests were excluded from this study, and a total of students were included in the analyses.

Informed consent was obtained from all subjects. The study was approved by institutional review board of a regional hospital KNUH Caffeine intake during the last 1 month was measured. All caffeinated drinks on the market were investigated and drinks and foods such as highly caffeinated energy drink, coffee, green tea, cola and chocolates were classified.

The product names and pictures were provided as a reference and intake was examined. The investigated amount of intake was converted into the intake per day. Personal history in the questionnaire included current height and weight and changes of height and weight over the last 1 year, current smoking habit and alcohol intake over the last 1 month, a diagnosis of depression and treatment by medical doctors, and the presence of other psychological or physical diseases were included.

Beck Depression Inventory BDI which was developed to evaluate the severity of depression 24 was used for the assessment of depression in this study. In majority of Korean studies, the standard cut-off scores are as follows: 0—9 indicates minimal depression, 10—15 indicates mild depression, 16—23 indicates moderate depression, and 24—63 indicates severe depression.

ISI, a measure of subjective severity of insomnia, developed by Bastien et al. Fifteen and above was interpreted as clinical insomnia. The level of stress was evaluated using Global Assessment of Recent Stress GARS and a higher score indicates a higher level of stress. Statistical analyses were conducted using IBM SPSS statistical software ver.

The subjects were divided into 4 groups according to caffeine intake. Pearson's chi-square test for nominal variables and analysis of variance test and Scheffe's test for continuous variables were used to compare the characteristics of each group. A total of adolescents in the second and third year of a middle school included male The average height was The average weight was Of them, 16 students were clinically diagnosed with depression 6.

According to the self-reported academic achievement, 80 students Two students who missed to fill out their academic achievement were classified into 'no response.

There were no statistically significant differences in sex, history of depression, and smoking habit between the groups. The height cm was taller in a group with a higher intake of caffeine Q1, Alcohol intake was higher in a group with a higher intake of caffeine Q1, The scores of BDI of the groups were 7.

The scores of BAI of the groups were 5. The ISI scores of the groups were 3. The GARS of each group was The OR of Q2, Q3, and Q4 to Q1 were 0. Due to the absence of the cutoff reference of GARS score, the average score of this study, 13, was used as the cutoff.

The OR of Q2, Q3, and Q4 to Q1 for the stress were 0. This study was conducted with a relatively large number of middle school students as a cross sectional study to evaluate the effects of caffeine intake on the psychological status of adolescents.

The results showed that a group with a higher caffeine intake tends to have a higher alcohol consumption, lower academic achievement and a higher score of depression, anxiety, insomnia, and stress.

When influential factors were adjusted, the severity of depression and anxiety increased with statistical significance. This result is contrasted to a previous study reporting that Korean adolescents tend to take a high dose of caffeine to keep awake during examination periods.

Moreover, the average daily caffeine intake in this study Therefore, two studies are not comparable. Furthermore, the influence of study periods and study areas cannot be overlooked. In our study, the amount of caffeine intake had a significant correlation with mild to severe depressive symptoms and borderline insomnia.

This result is consistent with previous studies showing that caffeine intake influences sleep 8 , 9 , 10 , 15 , 31 and causes daytime sleepiness affecting academic achievement.

In addition, persistent caffeine overdose can cause depression and lead to chronic depression as a withdrawal symptom even if caffeine intake is stopped. Several studies have demonstrated the relationship between caffeine and anxiety. The reason for this is that the study was conducted 2 weeks after the examination and anxiety might have been reduced at the point of the study period.

Considering the fact that the half-life of caffeine is 4—6 hours, it is meaningless to measure anxiety after several days or weeks and chronic effects on cognitive function and emotion is expected to be trivial, too.

The odds ratio between stress and caffeine intake showed an increasing tendency but there was no statistical significance, which is contrast to previous study results.

It is thought that the discrepancy is caused by the facts that the stress level was measured some time after the caffeine intake not during the caffeine intake and other influential factors associated with stress were not considered in the analyses.

There are several limitations that need to be addressed in this study. Firstly, this study was conducted 2 weeks after the examination and the fact that caffeine overdose in adolescents is characterized by intensive overdose during a short period of time was not considered when the study was designed.

Nevertheless, this limitation gave us an opportunity to examine usual habit and psychological status. Further studies on adverse effects of caffeine according to caffeine intake patterns by comparing the usual caffeine intake patterns and caffeine intake patterns during a specific period as well as the effects of addiction and withdrawal should be conducted.

Secondly, this study was limitedly conducted with the second and third year of middle school students in a city. Therefore, selection bias cannot be excluded. The differences of psychological status and life patterns between middle school students and other students elementary and high school students were not considered.

Moreover, students living in cities have a greater accessibility to caffeinated drinks than other areas. Thus, the results may differ depending on study locations. Thirdly, data was only collected by self-reported questionnaire. The height and weight were asked to the students instead of measuring them since the study was conducted in the school.

Academic achievement and the diagnosis of depression were also not verified due to ethical issues. It is also possible that the students were not completely honest during the psychological tests.

Lastly, the causality of the relationship cannot be identified since the study was conducted as a cross sectional study. Despite of the limitations, this study is significant because it is the first study that conducted with Korean middle school students to evaluate psychological effects of caffeine.

Whereas the effects of caffeine are well investigated in other countries, data on Korean population lacks especially on adolescent population. In addition, this study showed that negative effects of caffeine are greater in adolescents comparing to adult population.

The data can be used as evidence for health education. Canned coffee, coffee mix, and carbonated drink that are highly accessible drinks contain a large amount of caffeine.

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That is, neither the participants nor the researchers knew when the participants were receiving caffeine or the placebo.

To qualify for the study, the coffee drinkers were asked to fill out a daily diary of caffeine intake for a period of one week. They kept the diary in order to determine the average amount of caffeine they consumed on a daily basis, the type of caffeinated beverages they drank, and the variation from day to day, all of which helped verify the participants as habitual coffee drinkers.

Once the coffee drinkers qualified for the study, their responses to caffeine were measured on two different, randomly chosen days. On one day, the coffee drinkers were given a milligram dose of caffeine in the morning and again at lunchtime.

On the other day, they were given identical capsules containing a placebo at the same time interval. The doses of caffeine -- equal to four cups of coffee -- and the dosage times were chosen to reflect normal patterns of coffee drinking in adults. Half of the study participants received caffeine on the first day of study and the others received it on the second day.

The coffee drinkers were given, on average, two to three days off between study days during which they could consume as many caffeinated beverages as they normally desired.

On both study days, coffee drinkers wore a portable monitor that measured blood pressure and heart rate four times an hour from early morning until bedtime, while they went about their normal daily activities. They were asked to collect urine samples so that the researchers could measure the amount of stress hormones they had produced that day.

They were also asked to keep a diary to record their perceived stress levels as well as their physical position — standing, sitting or lying down — each time the monitor was activated.

When the researchers compared the caffeine days to the placebo days they discovered that caffeine consumption significantly raised systolic and diastolic blood pressure consistently throughout the day and night, and adrenaline levels rose by 32 percent.

The researchers found that the elevated levels persisted as the evening progressed to bedtime. The study also showed that while caffeine increases blood pressure and heart rate, it also amplifies those effects at the times when participants report higher levels of stress during their day, said Lane.

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Get active. Eat healthy. Very dry, irritated or tired eyes? But while the research itself is important, we must not forget that stress is a normal human reaction to events rather than brain chemistry.

The last thing we need is another psychiatric drug that ignores the root of the problem. Previous research has shown a number of positive effects of caffeine, for instance on preventing depression. This study is the first to uncover the neurochemical pathways that enable caffeine to prevent some of the negative effects of stress on the brain.

Caffeine is known to inhibit receptors in the brain for the chemical adenosine. The researchers found that these receptors also control the negative effects of chronic stress and that stress-induced behaviour can be reversed by blocking the receptors.

The results are important, as we do indeed know that chronic stress affects people very badly. In mice, the rather unpleasant stressful situations in this experiment included as damp bedding, sharing living space with others, food and water deprivation, cold baths and cages tilted at 45°.

And these poor mice unsurprisingly showed the behavioural and neurological consequences of this stress. In humans, chronic stress can also have disastrous consequences. For example, my colleagues have shown that the economic crisis in the years between and can be blamed for as many as 1, people in the UK taking their own lives.

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Ricardo Magalhães, Maria Picó-Pérez, Madalena Esteves, Rita Vieira, Teresa C. Castanho, Liliana Amorim, Mafalda Sousa, Ana Coelho, Joana Cabral, Pedro S.

NeuroSpin, CEA, CNRS, Paris-Saclay University, Gif-sur-Yvette, France. Center for Music in the Brain, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark. Psychological Neuroscience Lab, CIPsi, School of Psychology, University of Minho, Braga, Portugal.

You can also search for this author in PubMed Google Scholar. Correspondence to Nuno Sousa. The present study was conducted in accordance with the principles expressed in the Declaration of Helsinki 59th amendment and was approved by the ethics committee of Hospital de Braga.

All participants gave informed written consent after the study aims were explained and were informed of the option to withdraw from the study at any time.

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