Physiological changes during physical and psychological stress

Changes in urine catecholamines, blood pressure and heart rate during two physical exercise test sessions (35% VO_2max and 50% VO_2max) and one psychological stress session which involved reading under delayed auditory feedback (DAF) were compared. Increases in both the haemodynamic parameters and in the excretion of catecholamines were found in response to all three tests. The changes in adrenaline (A) did not differentiate between the test situations. Noradrenaline (NA) levels were significantly larger for physical exercise conditions and graded according to the relative workload. The ratio ΔNA/ΔA was similar for both physical tests but statistically different for the DAF session. Significant and positive correlations between haemodynamic parameters and catecholamine excretion were found only for the DAF test. These correlations and the differences in catecholamine excretion suggest different bodily responses to physical and psychological stress. These findings may have practical implications in industrial field studies.     

Impact of caffeine and psychological stress on blood pressure in black and white men

The purpose of this study was to examine the effects of caffeine and psychological stress on systolic blood pressure (SBP) and heart rate (HR) in 40 healthy Black and White male regular coffee drinkers. Half the subjects had a positive family history of hypertension (FH+), and half did not. The effects of 250 mg of caffeine versus placebo (3 mg) in decaffeinated coffee were compared in a within-subject, double-blind, cross-over design. SBP and HR were measured at rest, after caffeine ingestion, during mental arithmetic stress, and during recovery. Results confirmed previous findings with White men that a moderate dose of caffeine produced significant increases in SBP and little effect on HR and that the pressor effects of caffeine and stress combined additively. Contrary to expectations, no overall race or family history differences in SBP levels or in SBP reactivity were observed. FH+ Blacks, however, evidenced slower SBP recovery than Whites. Whites evidenced higher overall HR levels than blacks, but this difference was not specific to caffeine or to mental stress. Mechanisms of racial differences in reactivity underlying differential risk for hypertension are discussed, as well as the utility of caffeine as a pharmacologic probe for such differences.     

Human coffee drinking: manipulation of concentration and caffeine dose.

In a residential research ward coffee drinking was studied in 9 volunteer human subjects with histories of heavy coffee drinking. A series of five experiments was undertaken to characterize adlibitum coffee consumption and to investigate the effects of manipulating coffee concentration, caffeine dose per cup, and caffeine preloads prior to coffee drinking. Manipulations were double-blind and scheduled in randomized sequences across days. When cups of coffee were freely available, coffee drinking tended to be rather regularly spaced during the day with intercup intervals becoming progressively longer throughout the day; experimental manipulations showed that this lengthening of intercup intervals was not due to accumulating caffeine levels. Number of cups of coffee consumed was an inverted U-shaped function of both coffee concentration and caffeine dose per cup; however, coffee-concentration and dose-per-cup manipulations did not produce similar effects on other measures of coffee drinking (intercup interval, time to drink a cup, within-day distribution of cups). Caffeine preload produced dose-related decreases in number of cups consumed. As a whole, these experiments provide some limited evidence for both the suppressive and the reinforcing effects of caffeine on coffee consumption. Examination of total daily coffee and caffeine intake across experiments, however, provides no evidence for precise regulation (i.e., titration) of coffee or caffeine intake.     

Reinforcing effects of caffeine in coffee and capsules.

In a residential research ward the reinforcing and subjective effects of caffeine were studied under double-blind conditions in volunteer subjects with histories of heavy coffee drinking. In Experiment 1, 6 subjects had 13 opportunities each day to self-administer either a caffeine (100 mg) or a placebo capsule for periods of 14 to 61 days. All subjects developed a clear preference for caffeine, with intake of caffeine becoming relatively stable after preference had been attained. Preference for caffeine was demonstrated whether or not preference testing was preceded by a period of 10 to 37 days of caffeine abstinence, suggesting that a recent history of heavy caffeine intake (tolerance/dependence) was not a necessary condition for caffeine to function as a reinforcer. In Experiment 2, 6 subjects had 10 opportunities each day to self-administer a cup of coffee or (on different days) a capsule, dependent upon completing a work requirement that progressively increased and then decreased over days. Each day, one of four conditions was studied: caffeinated coffee (100 mg/cup), decaffeinated coffee, caffeine capsules (100 mg/capsule), or placebo capsules. Caffeinated coffee maintained the most self-administration, significantly higher than decaffeinated coffee and placebo capsules but not different from caffeine capsules. Both decaffeinated coffee and caffeine capsules were significantly higher than placebo capsules but not different from each other. In both experiments, subject ratings of "linking" of coffee or capsules covaried with the self-administration measures. These experiments provide the clearest demonstrations to date of the reinforcing effects of caffeine in capsules and in coffee.     

Interactive Effects of Caffeine Consumption and Stressful Circumstances on Components of Stress: Caffeine Makes Men Less,But Women More Effective as Partners Under Stress

We tested whether increased caffeine consumption exacerbates stress and disrupts team performance, and we explored whether “tend and befriend” characterizes women's coping. We gave decaffeinated coffees, half of which contained added caffeine, to coffee drinkers in same‐sex, same‐aged dyads. We measured individual cognitive appraisals, emotional feelings, bodily symptoms, coping, and performance evaluations, together with dyad memory, psychomotor performance, and negotiation skills under higher or lower stressful conditions. Evidence consistent with the first hypothesis was weak, but we found that women performed better than did men on collaborative tasks under stress, provided caffeine had been consumed. The usefulness of multi component, cognitive‐relational approaches to studying the effects of caffeine on stress is discussed, together with special implications of the effects for men.     

Cardiovascular reactivity, mood, and task performance in deprived and nondeprived coffee drinkers

Forty habitual, heavy coffee drinkers (M = 5.7 cups/day) participated in two experimental sessions. Participants were deprived of their morning coffee for one of the laboratory sessions, not deprived the other. During each session, subjects consumed 12 oz of caffeinated coffee, decaffeinated coffee, or caffeine-free herbal tea. Measurements of heart rate, blood pressure, mood, and catecholamine response to deprivation and consumption of the beverage, alone and in combination with challenging tasks, were made. This study found that caffeine continues to cause blood pressure increases with chronic, heavy consumption and that these effects do not appear to habituate with regular use. Subjects reacted to behavioral challenge with fewer negative mood effects if they had consumed caffeine or coffee. Mild caffeine deprivation was associated with symptoms of stress.     

BEHAVIORAL TREATMENT OF CAFFEINISM: REDUCING EXCESSIVE COFFEE DRINKING

Excessive coffee drinking can have deleterious effects because of the large amounts of caffeine that are ingested. Caffeine is thought to be addicting, and prolonged and excessive use can lead to caffeinism, a condition that has serious behavioral and physiological side effects. The present study developed and evaluated a treatment program to reduce excessive daily coffee drinking to moderate and presumably safer levels. Three habitual coffee drinkers received individualized changing criterion programs that systematically and gradually reduced their daily caffeine intake. The coffee drinkers were required to self-monitor and plot their daily intake of caffeine. They received monetary prizes for not exceeding the treatment phase criteria and forfeited a portion of their pretreatment deposit when they did. Their coffee drinking decreased from almost nine cups per day (over 1100 mg of caffeine) during baseline to less than three cups per day (less than 343 mg) at the end of treatment or a reduction of 69%. The treatment effect was maintained during a 10-month follow-up, averaging a 67% reduction from baseline. The program appears to be a reasonable method of reducing and then maintaining daily caffeine intake at less harmful levels.     

PSYCHOPHYSIOLOGICAL REACTIONS TO INFUSIONS OF A MIXTURE OF ADRENALINE AND NORADRENALINE

F rankenhaeuser , M. & J ärpe , G. Psychophysiological reactions to infusions of a mixture of adrenaline and noradrenaline. Scand. J. Psychol ., 1962, 3 , 21–29.—Psychophysiological reactions to a mixture of adrenaline and noradrenaline (average dose 6.99 + 6.99 μg/min.) given as a continuous intravenous drip for periods of about 40 min. were studied in 11 subjects. Control data were obtained from placebo infusions. The catecholamine infusions produced marked subjective and overt symptoms as well as changes in heart rate and blood pressure. These reactions were—on the whole—similar to those produced by infusions of adrenaline only. Time experience was also affected by the catecholamines in that more was retained of the previously perceived time intervals.     

Conditioning and the placebo effect: The effects of decaffeinated coffee on simple reaction time in habitual coffee drinkers

An experiment is reported in which reaction time was repeatedly assessed in six subjects (habitual coffee drinkers) up to 90 min after the administration of decaffeinated coffee (i.e. placebo), 250 mg caffeine in coffee and at equivalent times on control days. As predicted reaction time was shorter (but not significantly so) immediately after the administration of the two coffee preparations. This finding was taken to support the hypothesis that through a process akin to classical conditioning, drug effects may become associated with the cues that precede and are concurrent with their administration. The findings are critically assessed and related to previous studies. Finally, it is argued that the conditioning hypothesis can account for a number of clinical findings about the placebo response as observed in therapeutic trials.     

INTERINDIVIDUAL DIFFERENCES IN CATECHOLAMINE EXCRETION DURING STRESS

Measurements of adrenaline and noradrenaline excretion during inactivity and stress, and ratings of 22 personality variables were obtained for 110 subjects. Six factors were extracted by a factor analysis. Two of the factors were associated with personality variables, three primarily with catecholamines, and one with both types of variables. The 'mixed.' factor was tentatively interpreted as indicating that individuals with depressive tendencies respond to stressors with a relatively smaller rise in adrenaline excretion. This finding is in line with current theories concerning the role of catecholamines in affective psychoses.     

Night-rest urinary catecholamine excretion in relation to aspects of free time, work and background data in a teacher group

Free time, work and background data were related to night-rest catecholamine excretion rates in a teacher group (n = 137) during an autumn term. The explained interindividual variance increased slightly towards the end of the term. Adrenaline excretion was predicted better than noradrenaline, notedly by coffee consumption, amount of physical activity, and subjective stress feelings which explained 16% of the variance in adrenaline excretion during night rest. However, the results indicated that the differences in catecholamine excretion during night rest remained mostly unpredictable.     

Catecholamine training effects from exercise programs: A bridge to exercise-temperament relationships

Three studies were conducted to test whether a catecholamine training effect results from a long-term aerobic exercise program. Study I showed significant increases in urinary adrenaline and noradrenaline following moderate mental stress/challenge for male aerobics subjects after a semester of training. Control groups of nonexercisers and continuously in-condition marathoners showed no comparable pre- to post semester catecholamine increases. Male and female Aerobics subjects were contrasted with nonexercisers across a semester in Study 2; the hypothesis was confirmed that postsemester increases in catecholamines occurred only following an episode of mental challenges/stress, and not following base-rate-rest conditions. Under conditions of more active challenge than in Studies 1 and 2, women subjects in Study 3 provided directional but nonsignificant support for the Study 2 findings. The results are discussed in the context of literature on the relationship of catecholamine availability during challenge/stress to temperament and on the relationship of aerobic training to temperament. At a theoretical level, the question is discussed of increased catecholamine availability being a likely mediator in the exercise program to temperament relationship.This research was supported by a grant from the Research Council of the University of Nebraska Lincoln. Our thanks to Prof. James Crabbe for assistance in recruiting subjects in Study 2, and to Pamela Brown and Prof. Wes Sime for assistance with Study 3.     

Hypertension risk and caffeine's effect on cardiovascular activity during mental stress in young men

Examined the cardiovascular effects of caffeine plus behavioral stress in men low versus high in risk of essential hypertension. Caffeine (3.3 mg/kg, equivalent to 2 to 3 cups of coffee) or placebo was given on alternate days to 19 low-risk men (negative for parental hypertension and low-normal resting blood pressure, BP) and 20 high-risk men (positive history, high-normal BP). Forty minutes later, each worked for 15 min on a demanding psychomotor task during which BP, cardiac output, and vascular resistance were determined. During rest, caffeine raised vascular resistance in both groups. During the task, it supra-additively increased the systolic BP response by enhancing the rise in cardiac output, producing equivalent BP rises in both groups. Due to the higher resting pressures of the high-risk men, caffeine plus the task resulted in 50% of these having transient BP of 140/90 mg Hg or greater. Caffeine in combination with mental stress may produce undesirable BP in those at risk for hypertension.     

Effects of flight workload on urinary catecholamine responses in experienced military pilots

This study investigated the flight responses induced by strenuous aerobatic demonstration flight and an air-to-air combat maneuvering flight in experienced pilots. Subjects were 54 military male pilots on a volunteer basis: 8 T-4 pilots (M= 35.8 yr., SD=4.9), 15 F-4 pilots (M=32.6 yr., SD=5.1), 13 F-15 pilots (M=33.8 yr., SD=1.0), and 18 F-2 pilots (M=33.7 yr., SD=3.9). Samples of urine were collected approximately 30 min. before and 20 min. after the flights. The postflight adrenaline in all pilots was significantly higher than at preflight, while a significant increase in noradrenaline at postflight was not observed. The post-/preflight ratio of adrenaline in all pilots was relatively similar and high. These findings might be regarded as a result of autonomic nervous system response to the flight workload of military pilots. Especially is increment in sympathetic activity considered to play an important part in psychological adaptation to flight.     

Inhibitory avoidance deficit following short-term adrenalectomy in the rat: the role of adrenal catecholamines

Impaired retention of an inhibitory avoidance response was observed in rats subjected to adrenalectomy (ADX) up to 120 hr before the single learning trial. Corticosterone substitution failed to normalize this behavioral deficit. Rats ADX 240 hr prior to the learning trial showed a normalized behavior. Adrenomedullectomy (ADXM) 48 or 240 hr before learning caused a similar impairment as in short-term ADX rats. The 240-hr ADX rats subjected to corticosterone substitution showed the same behavioral deficit as short-term ADX rats or ADXM ones. Immediate postlearning subcutaneous injection of adrenaline in a dose range of 0.005-5.0 micrograms/kg or of noradrenaline (0.005-0.5 microgram/kg) to 48-hr ADX rats resulted in a dose-related improvement of later retention behavior. Higher doses of catecholamines were less or ineffective. Postlearning treatment of 48-hr ADXM rats with adrenaline (0.5-500 micrograms/kg) caused a similar pattern of behavioral changes. It is concluded that adrenal catecholamines play an important role in the modulation of consolidation of memory. In addition, the high circulating ACTH levels that follow long-term ADX may correct for the behaviorial deficit induced by the absence of adrenomedullary catecholamines.     

Percolating ideas: The effects of caffeine on creative thinking and problem solving

Caffeine is the most widely consumed psychotropic drug in the world, with numerous studies documenting the effects of caffeine on people’s alertness, vigilance, mood, concentration, and attentional focus. The effects of caffeine on creative thinking, however, remain unknown. In a randomized placebo-controlled between-subject double-blind design the present study investigated the effect of moderate caffeine consumption on creative problem solving (i.e., convergent thinking) and creative idea generation (i.e., divergent thinking). We found that participants who consumed 200 mg of caffeine (approximately one 12 oz cup of coffee, n = 44), compared to those in the placebo condition (n = 44), showed significantly enhanced problem-solving abilities. Caffeine had no significant effects on creative generation or on working memory. The effects remained after controlling for participants’ caffeine expectancies, whether they believed they consumed caffeine or a placebo, and changes in mood. Possible mechanisms and future directions are discussed.     

The acute effects of caffeine on evoked response,vigilance, and activity level in hyperkinetic children

Seventeen hyperkinetic children who had previously responded to sympathomimetic amines were given three different dosages of caffeine in counterbalanced order (placebo, and low and high doses equivalent to one and three cups of coffee). One hour following ingestions they were tested, double-blind on measures of visual evoked response, alpha time, vigilance, and activity level. There was a significant effect on evoked response. The behavioral measures tended to be affected in a dose-related manner but not to a statistically significant degree. It is concluded that although centrally active, caffeine does not show the congruence between behavioral and central effects that other stimulants useful in behavioral management have shown.     

Catecholamine output in school children as related to performance and adjustment

Johansson, G. Frankenhaeuser, M. & Magnusson, D. Catecholamine output in school children as related to performance and adjustment. Scand. J. Psychol., 1973, 14, 20–28.-Excretion of two catecholamines, adrenaline and noradrenaline, was studied in a group of 240 children, sampled from a longitudinal study, during a "passive" period (viewing a film) and a subsequent "active" period (performing an arithmetic test). In the group of boys the mean adrenaline excretion increased significantly during the active as compared with the passive period. Among the children of both sexes, those who increased their adrenaline output during the arithmetic test as compared with the preceding passive period, performed better on the test in terms of speed and endurance, than did children who did not respond to mental work by adrenaline increase. Significant positive correlations were found between the secretion of both catecholamines and teachers' ratings indicating good social adjustment and emotional stability, as well as with measures of the pupils' subjective satisfaction with their school environment.     

Role of monoamines in the control by hormones of sexual receptivity in the female rat.

The involvement of indole- and catecholamines in the hormonal regulation of sexual receptivity has been investigated in ovariectomized female rats. Drugs that reduce 5-hydroxytryptamine, dopamine, and adrenaline or increase noradrenaline neurotransmission tended to facilitate the occurrence of estrous behavior in estrogen-treated females, and drugs having opposite effects tended to inhibit receptivity induced by estrogen and progesterone. Estrogen decreased noradrenaline turnover in cortex and brain stem; progesterone enhanced this effect in brain stem but prevented it in cortex. Both hormones tended to block noradrenaline uptake in hypothalamus in vitro. In a schedule used to induce receptivity, estrogen accelerated serotonin turnover, an effect prevented by progesterone. Thus a number of monoamines may be involved in the control by hormones of estrous behavior. Furthermore, hormones affect both amine turnover and uptake mechanisms.     

The effects of smoking and urinary pH on a detection task

Performance was measured in a detection task over a period of 50 min. Subjects were either non-smokers or smoked more than 15 cigarettes per day. No smoking was allowed during the task, but smokers were all asked to smoke a cigarette immediately before doing it. One hour previously, subjects had been given a double-blind dose of a substance which would shift the pH of their urine either upwards or downwards, by small amounts sufficient to affect the rate of renal excretion of nicotine in the smokers. The pH manipulation had no effect on the performance of the non-smokers, who improved steadily throughout the task. After some 40 min of performance, the deprived smokers showed less improvement than the non-smokers, and the smokers whose urine had been made acid improved less than those whose had been made alkaline. The results are interpreted as evidence for a phasic effect on performance of small degrees of nicotine deprivation, which has consequences for theories of nicotine dependence.