Investigation of the effects and aftereffects of naturally occurring upper respiratory tract illnesses on mood and performance

Fever Dreams: An Online Study

In addition to a large variety of somatic symptoms, fever also affects cognition, sleep, and mood. In an online survey with 164 participants, 100 fever dream reports were submitted. Fever dreams were more bizarre and more negatively toned and included more references to health and temperature perception compared to "normal" most recent dreams - findings that are in line with the continuity hypothesis of dreaming. Future studies should follow up this line of research by conducting diary studies during naturally occurring febrile illnesses and sleep laboratory studies with experimentally induced fever. It would also be very interesting to study the effect of thermal stimulation applied during sleep on dream content. This research helps to understand subjective experiences while sleeping in an extreme condition (elevated body temperature).

Task Engagement and Attentional Resources

OBJECTIVE

Two studies tested multivariate models of relationships between subjective task engagement and vigilance. The second study included a stress factor (cold infection). Modeling tested relationships between latent factors for task engagement and vigilance, and the role of engagement in mediating effects of cold infection.

BACKGROUND

Raja Parasuraman's research on vigilance identified several key issues, including the roles of task factors, arousal processes, and individual differences, within the framework of resource theory. Task engagement is positively correlated with performance on various attentional tasks and may serve as a marker for resource availability.

METHOD

In the first study, 229 participants performed simultaneous and successive vigilance tasks. In the second study, 204 participants performed a vigilance task and a variable-foreperiod simple reaction-time task on two separate days. On the second day, 96 participants performed while infected with a naturally occurring common cold. Task engagement was assessed in both studies.

RESULTS

In both studies, vigilance decrement in hit rate was observed, and task performance led to loss of task engagement. Cold infection also depressed both vigilance and engagement. Fitting structural equation models indicated that simultaneous and successive tasks should be represented by separate latent factors (Study 1), and task engagement fully mediated the impact of cold infection on vigilance but not reaction time (Study 2).

CONCLUSIONS

Modeling individual differences in task engagement elucidates the role of resources in vigilance and underscores the relevance of Parasuraman's vision of the field.

APPLICATION

Assessment of task engagement may support diagnostic monitoring of operators performing tasks requiring vigilance.

The Common Cold Impairs Visual Attention, Psychomotor Performance and Task Engagement

A study was conducted to test the effects of naturally-occurring colds on visual attention, psychomotor performance and subjective indices of stress. 204 participants performed a battery of tasks assessing simple reaction time, focused attention, categoric search and vigilance, on two separate occasions. Affective, motivational and cognitive stress state dimensions were measured using a validated questionnaire. On the first occasion, all participants were healthy. On the second occasion, approximately half the sample suffered from a cold. Comparison of cold sufferers with healthy controls showed significant cold effects. In the cold group, response was slower on simple reaction time and focused attention tasks, and detection rate on the vigilance task was lower. Colds reduced subjective task engagement (e.g., lower energy and motivation) and increased distress (e.g., more negative mood). Regression analysis indicated a direct effect of colds on simple reaction time, whereas the cold effect on vigilance appeared to be statistically mediated by reduced task engagement. It is concluded that colds can produce operationally-significant performance deficits on a variety of attentional tasks.

Effects of upper respiratory tract illnesses, ibuprofen and caffeine on reaction time and alertness

RATIONALE

Compared with healthy individuals, those with upper respiratory tract illnesses (URTIs) report reduced alertness and have slower reaction times. It is important to evaluate medication that can remove this behavioural malaise.

OBJECTIVES

The aim of this study was to compare the effects of a combination of ibuprofen plus caffeine with ibuprofen and caffeine alone, and placebo on malaise associated with URTIs, as measured by psychomotor performance and mood testing.

METHODS

Volunteers were randomly assigned to one of four medication conditions as follows: 200 mg ibuprofen and 100 mg caffeine; 200 mg ibuprofen; 100 mg caffeine; placebo. A single oral dose was given and testing followed for 3 h. Efficacy variables were based on the volunteers' performance, measured by psychomotor performance and mood.

RESULTS

The pre-drug results confirmed that those with an URTI had a more negative mood and impaired performance. Results from the simple reaction time task, at both 55- and 110-min post-dosing, showed that a single-dose of caffeinated products (I200/C100 and CAF100) led to significantly faster reaction times than IBU200 and placebo. These effects were generally confirmed with the other performance tasks. Subjective measures showed that the combination of ibuprofen and caffeine was superior to the other conditions. There were no serious adverse events reported, and study medication was well tolerated.

CONCLUSIONS

The results from the post-drug assessments suggest that a combination of ibuprofen and caffeine was the optimum treatment for malaise associated with URTIs in that it had significant effects on objective performance and subjective measures.

Twenty-five years of research on the behavioural malaise associated with influenza and the common cold

Minor illnesses such as the common cold and influenza are frequent and widespread. As well as specific symptoms such as nasal problems and fever, these illnesses are associated with a behavioural malaise. One feature of this malaise is reduced alertness and this has been confirmed using subjective reports and objective measures of performance. Such effects have been obtained with both experimentally induced infections and in studies of naturally occurring illnesses. The mechanisms underlying the effects are unclear but possibly reflect effects of cytokines on the CNS which result in changes in neurotransmitter functioning that lead to reduced alertness. The malaise induced by these illnesses has many real-life consequences and activities such as driving and safety at work may be at risk. These illnesses not only have direct effects on performance and mood but also make the person more sensitive to effects of other negative influences such as noise, alcohol and prolonged work. Countermeasures include ingestion of caffeine and other drugs known to increase alertness.

Effects of chewing menthol gum on the alertness of healthy volunteers and those with an upper respiratory tract illness

Recent research has shown that chewing gum increases subjective alertness. Upper respiratory tract illnesses (URTIs) lead to reduced alertness, and it has been shown that stimulants such as caffeine can reverse this effect. It is now important to determine whether menthol chewing gum can produce a similar effect. Young adults with an URTI (N = 16) and a healthy control group (N = 12) rated their mood and symptoms on two occasions (the first when those with a URTI were ill and the second when both groups were healthy). During each session, volunteers provided a rating while chewing gum and when they were not chewing. Those with a URTI reported reduced alertness, which persisted into convalescence. Chewing gum was associated with greater alertness in both those with URTIs and the healthy group. Chewing gum reduced the severity of nasal symptoms in those with a cold. The effects of the URTI and menthol gum may reflect changes in trigeminal stimulation.

Behavioral effects of upper respiratory tract illnesses: a consideration of possible underlying cognitive mechanisms

Previous research has shown that both experimentally induced upper respiratory tract illnesses (URTIs) and naturally occurring URTIs influence mood and performance. The present study investigated possible cognitive mechanisms underlying the URTI-performance changes. Those who developed a cold (N = 47) had significantly faster, but less accurate, performance than those who remained healthy (N = 54). Illness had no effect on manipulations designed to influence encoding, response organisation (stimulus-response compatilibility) or response preparation. Similarly, there was no evidence that different components of working memory were impaired. Overall, the present research confirms that URTIs can have an effect on performance efficiency. Further research is required to identify the physiological and behavioral mechanisms underlying these effects.

Common Respiratory Tract Infections as Psychological Entities: A Review of the Mood and Performance Effects of Being Ill

The clinical manifestations associated with colds and influenza overshadow the equally important mood and performance impairments. While decreased alertness and increased anxiety can be considered side effects of symptomatology, symptoms alone may not be responsible for the psychomotor and attention deficits of colds and influenza, respectively. An alternative hypothesis, as proposed in this review, suggests that the immune response, in the form of a cytokine cascade, may be responsible for both the physical and psychological symptoms. In particular, patterns of cytokine production for each infection will dictate the symptoms and performance deficits both within and between viruses. This hypothesis can be extended to incorporate infectious mononucleosis, as well as colds and influenza. The efficacy of symptom‐based overthe‐counter medications is then called into question.

Intranasal immune challenge induces sex-dependent depressive-like behavior and cytokine expression in the brain

The association between activation of the immune system and mood disorders has been reported by several studies. However, the mechanisms by which the immune system affects mood are only partially understood. In the present study, we detected depressive-like behavior in a rat animal model which involves the induction of inflammation in the nasal cavities by intranasal (i.n.) instillation of bacterial lipopolysaccharides (LPS). Female rats showed depressive-like behavior as evidenced by the forced swim test after repeated i.n. administration of LPS. These responses were not paralleled by alterations in motor activity as measured by the open field test. In the same animals, corticosterone responses after the swimming sessions were the highest of all the groups evaluated. Real-time RT PCR was used to analyze the transcriptional regulation of the cytokines interleukin-1beta, tumor necrosis factor-alpha, and interleukin-6 in several brain regions. Increased tumor necrosis factor-alpha was detected in the hippocampus and brainstem of female rats challenged with i.n. LPS. These results suggest that peripheral inflammation in the upper respiratory tract is an immune challenge capable of inducing depressive-like behavior, promoting exaggerated glucocorticoid responses to stress, and increasing cytokine transcription in the brain. These results further our understanding of the role that the immune system may play in the pathophysiology of depression.

Selective effects of upper respiratory tract infection on cognition, mood and emotion processing: a prospective study

Observational and experimentally induced infection studies show that upper respiratory tract infections (URTI) affect mood and cognition. This study tested the effects of naturally occurring URTI on cognition, mood and emotional processing, using a prospective design, with a broader array of tests than previous research, and with well matched control participants. Eighty participants (42 younger, M age 20.3 years; 38 older, M age 64.3 years) underwent neuropsychological assessment at baseline. Once a participant had URTI symptoms, s/he and a healthy, matched participant were retested. The Cognitive Drug Research computerised assessment battery was used to assess Power and Continuity of Attention, Quality of Episodic and Working Memory, Speed of Memory, and mood. Additionally, emotional processing was measured on matching of emotionally-negative faces with faces and faces with labels. Forty-two of 80 participants were matched (21 well, 21 ill). Well participants improved in Speed of Memory and face-label reaction time. Despite a lack of fever, ill participants demonstrated significantly smaller improvements. Older participants reported feeling less alert if ill, and less stressed if well, than at baseline. All ill participants reported less contentment than at baseline than well participants. Severity of URTI symptoms correlated with changes in Speed of Memory and mood. Even without fever, infectious disease produces large disturbances in speed of cognitive processing, particularly that reflecting retrieval from memory, and these effects are more marked in older participants. URTIs also affect mood. Future studies need to examine the role of inflammatory molecules and the brain regions implicated in mediating these findings.

Immunity and emotions: lipopolysaccharide increases defensive behaviours and potentiates despair in mice

Many studies have pointed out the relationships between immunity and depression, supporting a neuroimmune hypothesis of depressive disorders. However, despite the growing interest for such a hypothesis and the amount of clinical and experimental data available, the precise nature of this relationship between immunity and depression remains unclear. The present study aimed to investigate further the link between depression and immunity in mice using the modified version of the forced-swimming test. Based on a two-session test, results from our first experiment showed that endotoxin enhanced active defensive behaviours in mice during the first exposure to water, but was associated with increased immobility (i.e., 'behavioural despair') in the subsequent session. In our second experiment, we showed that these effects were blocked by a chronic antidepressant treatment with imipramine. Finally, we suggest a link between immunity and depression, based on the behavioural context in which immune activation takes place. We hypothesize that immune activation, by enhancing reactivity to the negative features of a given situation, increases defensive motivation of subjects, but therefore makes them more vulnerable to the deleterious emotional consequences of failure in defensive strategies.

Neuroimmune-endocrine crosstalk in schizophrenia and mood disorders

This review focuses on possible causes and the impact of different immune states in schizophrenia and major depression. It discusses the fact that, in schizophrenia, an over-activation of the type 2 immune response may dominate, while the type 1 and the pro-inflammatory immune responses are over-activated in major depression. The consequence of these diverse immune states is the activation and, respectively, inhibition of different enzymes in tryptophan/kynurenine metabolism, which may lead to an overemphasis of N-methyl-D-aspartate (NMDA) receptor antagonism in schizophrenia and of NMDA-receptor agonism in depression, resulting in glutamatergic hypofunction in schizophrenia and glutamatergic hyperfunction in major depression. In addition, the activation of the type 1 and the pro-inflammatory immune responses in major depression result in increased serotonin degradation and a serotonergic deficit. While antipsychotics and antidepressants today mainly act on the dopaminergic-glutamatergic and the noradrenergic-serotonergic neurotransmission, anti-inflammatory and immune-modulating therapies might act more basically at the pathophysiological mechanism. The limitations of this concept, however, are critically discussed.

Cytokines and major depression

In the research field of psychoneuroimmunology, accumulating evidence has indicated the existence of reciprocal communication pathways between nervous, endocrine and immune systems. In this respect, there has been increasing interest in the putative involvement of the immune system in psychiatric disorders. In the present review, the role of proinflammatory cytokines, such as interleukin (IL)-1, tumour necrosis factor (TNF)-alpha and interferon (IFN)-gamma, in the aetiology and pathophysiology of major depression, is discussed. The 'cytokine hypothesis of depression' implies that proinflammatory cytokines, acting as neuromodulators, represent the key factor in the (central) mediation of the behavioural, neuroendocrine and neurochemical features of depressive disorders. This view is supported by various findings. Several medical illnesses, which are characterised by chronic inflammatory responses, e.g. rheumatoid arthritis, have been reported to be accompanied by depression. In addition, administration of proinflammatory cytokines, e.g. in cancer or hepatitis C therapies, has been found to induce depressive symptomatology. Administration of proinflammatory cytokines in animals induces 'sickness behaviour', which is a pattern of behavioural alterations that is very similar to the behavioural symptoms of depression in humans. The central action of cytokines may also account for the hypothalamic-pituitary-adrenal (HPA) axis hyperactivity that is frequently observed in depressive disorders, as proinflammatory cytokines may cause HPA axis hyperactivity by disturbing the negative feedback inhibition of circulating corticosteroids (CSs) on the HPA axis. Concerning the deficiency in serotonergic (5-HT) neurotransmission that is concomitant with major depression, cytokines may reduce 5-HT levels by lowering the availability of its precursor tryptophan (TRP) through activation of the TRP-metabolising enzyme indoleamine-2,3-dioxygenase (IDO). Although the central effects of proinflammatory cytokines appear to be able to account for most of the symptoms occurring in depression, it remains to be established whether cytokines play a causal role in depressive illness or represent epiphenomena without major significance.

Effects of upper respiratory tract illnesses in a working population

The aim of the present study was to assess the impact of upper respiratory tract illnesses on efficiency at work. This was done using the 'after-effect' technique with measurements being taken before and after work and the difference between these giving an indication of efficiency over the day. All of the volunteers (N = 48) were tested when healthy to provide baseline data for simple reaction time and mood. When volunteers developed an upper respiratory tract illness (URTI) they (N = 16) repeated the procedure. Those who remained healthy over a three month period (N = 32) were recalled as healthy controls. In addition to the performance test and mood ratings the volunteers kept a sleep log and also rated how demanding the day had been and how much effort they had put in. The results showed that those with URTIs had slower reaction times and a more negative mood both before and after work. Illness did not have an effect on ratings of demand and effort. Those who were ill reported greater sleep disturbance but this could not account for the impaired performance or negative mood states. These results suggest that upper respiratory illnesses may impair performance and well-being at work.

Illness, cytokines, and depression

Various medical conditions that involve activation of the immune system are associated with psychological and neuroendocrine changes that resemble the characteristics of depression. In this review we present our recent studies, designed to investigate the relationship between the behavioral effects of immune activation and depressive symptomatology. In the first set of experiments, we used a double-blind prospective design to investigate the psychological consequences of illness in two models: (1) vaccination of teenage girls with live attenuated rubella virus, and (2) lipopolysaccharide (LPS) administration in healthy male volunteers. In the rubella study, we demonstrated that, compared to control group subjects and to their own baseline, a subgroup of vulnerable individuals (girls from low socioeconomic status) showed a significant virus-induced increase in depressed mood up to 10 weeks after vaccination. In an ongoing study on the effects of LPS, we demonstrated significant LPS-induced elevation in the levels of depression and anxiety as well as memory deficits. These psychological effects were highly correlated with the levels of LPS-induced cytokine secretion. In parallel experiments, we demonstrated in rodents that immune activation with various acute and chronic immune challenges induces a depressive-like syndrome, characterized by anhedonia, anorexia, body weight loss, and reduced locomotor, exploratory, and social behavior. Chronic treatment with antidepressants (imipramine or fluoxetine) attenuated many of the behavioral effects of LPS, as well as LPS-induced changes in body temperature, adrenocortical activation, hypothalamic serotonin release, and the expression of splenic TNF-alpha mRNA. Taken together, these findings suggest that cytokines are involved in the etiology and symptomatology of illness-associated depression.

After-effects of the common cold on mood and performance

The present study examined whether volunteers who had recently had common colds showed impairments in mood and performance in the weeks following the illness. All volunteers (n = 24) were tested when healthy to provide baseline data for simple and choice reaction time tasks, attention and memory tasks and ratings of mood. When participants developed a cold (n = 13) they returned to the laboratory so that the illness could be verified. When they were symptom free they returned to the laboratory and repeated the procedure. They then completed the study with a final session 1 week later. Volunteers (n = 11) who remained healthy over 10 weeks were recalled as controls and also repeated the procedures. The results showed that those who had recently had colds showed few impairments in mental performance and mood. Taken together with the results of previous studies, this suggests that after-effects of viral infection are largely restricted to severe illnesses such as infectious mononucleosis and influenza. After-effects of colds may occur but these probably reflect poor learning at the time of the illness.

Effects of upper respiratory tract illnesses on mood and performance over the working day

The present study examined whether volunteers with common colds showed impairments in objective and subjective indicators of alertness over the course of the working day. All the volunteers (n = 21) were tested when healthy to provide baseline data for simple and choice reaction time tasks, visual search tasks and ratings of mood. These measures were taken before work (08.30 hours), at lunchtime (13.00) and after work (17.30). When participants developed a cold (n = 6) they repeated the procedure. Volunteers (n = 15) who remained healthy were recalled as controls and also repeated the procedures. The results showed that those with colds had significantly slower simple and choice reaction times, and felt less alert, more tense and less sociable. The effects of having a cold on simple reaction time, alertness and anxiety increased over the day. This extends earlier research and shows that some of the effects of upper respiratory tract illnesses on mood and performance will depend on when assessments are made. These results also imply that performance and well-being at work will be impaired by upper respiratory tract illnesses.

Effects of an experimentally induced rhinovirus cold on sleep, performance, and daytime alertness

STUDY OBJECTIVES

There is accumulating evidence that the common cold produces impairments in psychomotor vigilance. This has led some investigators to hypothesize that such illnesses may also have disruptive effects on sleep. While several self-report studies suggest that viral illness may influence sleep parameters, no studies have assessed polysomnographically recorded sleep following viral infections.

DESIGN

Parallel control group comparison.

SETTING

Sleep laboratory in a large urban medical center.

PARTICIPANTS

Twenty-one men and women with susceptibility to the rhinovirus type 23.

INTERVENTIONS

Nasal inoculation with rhinovirus type 23.

MEASUREMENTS

Polysomnographically recorded sleep for five nights (2300-0700 h) post-viral inoculation. Twice daily (1030 and 1430 h) performance assessment during each experimental day using auditory vigilance and divided attention tasks. A multiple sleep latency test (MSLT) was performed daily for the duration of the study.

RESULTS

In symptomatic individuals, total sleep time decreased an average of 23 min, consolidated sleep decreased an average of 36 min, and sleep efficiency was reduced by an average of 5% during the active viral period (experimental days/nights 3-5) compared with the incubation period. Psychomotor performance was impaired. These changes were significantly greater than those observed in asymptomatic individuals.

CONCLUSIONS

The common cold can have detrimental effects on sleep and psychomotor performance in symptomatic individuals during the initial active phase of the illness.

Delayed effects of stress and immune activation

Stress responses play a crucial adaptive role but impose potentially subversive demands on the organism. The same holds for the symptoms of illness as seen after immune activation by pathogens or tissue damage. The responses to immune stimuli and stressors show remarkable similarities and rely on similar control mechanisms in the brain: i.e. they involve neuropeptides of the corticotropin releasing factor (CRF) family. Immune and non-immune challenges lead to responses that normally show a temporal relationship with the duration and intensity of the stimulus and the (re)activity of the stress-responsive systems return to their pre-challenged state within hours or days. However, exposure of animals or man to specific stimuli can induce delayed and long-lasting (weeks, months) alternation in stress responsive systems, resulting in a prolonged period of increased stress vulnerability. Immune stimuli are particularly powerful in eliciting such a stress vulnerable state. Various adaptive changes in the (neuro)biological substrate as seen during this stress vulnerable state also occur in depression, and may be causally related to the depressive symptoms that are often associated with infectious and inflammatory diseases.

Sickness and behaviour in animals: a motivational perspective

Proinflammatory cytokines, produced by the activated immune system, induce a whole set of non-specific symptoms in the infected individual (i.e. hypophagia, adipsia, reduced social interest). However, evidence summarised in this review shows that behavioural changes induced by cytokines are not merely the consequence of a degraded state but reflect motivational reorganisation. If the set-up of these new priorities is expressed by a general decrease in behavioural activities (e.g. immobility, sleepiness), the sick individual remains nevertheless an open system still able to respond to environmental stimuli. If these cues are evaluated as relevant to the new priorities (e.g. cues from scattered pups or cues from nest material when ambient temperature is low), the sick individual interrupts sickness behaviour in order to respond specifically to the cues (e.g. retrieving of the pups or nest building). Once this is done, there is a return to recuperative behaviour. These findings represent a primary characterisation of biobehavioural action of immune stimuli, and they open new perspectives to facilitate further progress in our understanding of cytokine effects on behaviour.

The effects of idazoxan on reaction times, eye movements and the mood of healthy volunteers and patients with upper respiratory tract illnesses

An experiment was carried out to determine whether idazoxan, a drug which increases the turnover of central noradrenaline, removes the malaise (reduced alertness, slower psychomotor performance) associated with upper respiratory tract illness (URTI). Eighty-one volunteers were tested when healthy and 17 returned to the laboratory when they developed URTIs. Those who remained healthy were then recalled as a control group. Volunteers were tested before and after receiving either idazoxan (40mg) or a lactose placebo. Idazoxan removed the URTI-induced slowing in a simple reaction time task and this group performed at a comparable level to the healthy group. No significant stimulant effect of idazoxan was found in the healthy subjects. The results suggest that at least part of the malaise induced by URTIs may reflect reductions in central noradrenaline and that this can be reversed by compounds such as idazoxan.

Effects of the Common Cold on Subjective Alertness, Reaction Time, and Eye Movements

Abstract The present study examined whether volunteers with common colds showed impairments in objective and subjective indicators of alertness. All the volunteers (N = 81) were tested when healthy to provide baseline data for mood, simple and choice reaction time tasks, and an anti-saccadic eye movement task. When subjects developed a cold (N = 17) they returned to the laboratory and repeated the procedure. Volunteers (N = 64) who remained healthy over a 10-week period were recalled as controls. The results showed that those with colds felt significantly less alert and had significantly slower simple and choice reaction times and eye movements. This extends earlier research and shows that electrophysiological measures may also be of use in assessing the behavioral changes induced by upper respiratory tract illnesses.

Effects of the common cold on mood and performance

Previous research has shown that both experimentally-induced and naturally occurring upper respiratory tract illnesses (URTIs) influence mood and mental functioning. None of the previous studies of naturally occurring colds has conducted appropriate virological assays to determine the nature of the infecting agent. This is an essential methodological step in studies of malaise associated with URTIs. The aim of this research was to investigate the effects of naturally occurring colds on mood and objective measures of performance. This was done by first conducting a cross-sectional comparison of 37 healthy people and 158 volunteers with colds and then a longitudinal study in which 100 volunteers developed colds and 87 remained healthy. Virological techniques were used to identify infecting agents and comparisons made across the different groups. The results showed that having a cold was associated with reduced alertness and slowed reaction times. These effects were observed both for colds where the infecting virus was identified and those where it was not. Similar effects were obtained for both rhinovirus and coronavirus colds. One may conclude that upper respiratory tract illnesses lead to a reduction in subjective alertness and impaired psychomotor functioning. This was true for both illnesses where the infecting agent was identified and for those clinical illnesses where no virus was detected. It is now important to identify the mechanisms linking infection and illness with the behavioural changes. Similarly, the impact of these effects on real-life activities such as driving needs examining. Finally, methods of treatment need to be developed which not only treat the local symptoms of the illnesses but remove the negative mood and the performance impairments.

Influence of socioeconomic status on behavioral, emotional and cognitive effects of rubella vaccination: a prospective, double blind study

A double-blind prospective design was used to investigate the immediate and prolonged psychological effects of a specific viral infection, and the role of immune activation in mediating these effects. Subjects were 240 female teenager girls who were vaccinated with rubella vaccine. Based on analysis of levels of antibodies to rubella, subjects were divided into two groups. An experimental group (n = 60), which included subjects who were initially seronegative and were infected following vaccination, and a control group (n = 180), which included subjects who were already immune to rubella before vaccination. Compared with the control group and to their own baseline, low socioeconomic status (SES) subjects within the experimental group showed a significant increase in the severity of depressed mood, social and attention problems, and delinquent behavior. Ten weeks post-vaccination there were no differences between the experimental and control groups in serum levels of interleukin-1 beta, interferon-gamma, soluble interleukin-2 receptors (sIL-2r), and cortisol. However, a significant negative correlation was found between fatigue-related symptoms and sIL-2r levels in the experimental (r = -0.325), but not the control group (r = -0.046). These findings suggest that viral infection can produce prolonged behavioral, emotional and cognitive problems mainly in subjects belonging to the low SES.

Caffeine and the common cold

An experiment was carried out to determine whether caffeinated and decaffeinated coffee removed the malaise (reduced alertness, slower psychomotor performance) associated with having a common cold. One hundred volunteers were tested when healthy and 46 returned to the laboratory when they developed colds. Those subjects who remained healthy were then recalled as a control group. On the second visit subjects carried out two sessions, one pre-drink and another an hour after the drink. Subjects were randomly assigned to one of the following three conditions, caffeinated coffee (1.5 mg/kg caffeine/body weight), decaffeinated coffee or fruit juice. Subjects with colds reported decreased alertness and were slower at performing psychomotor tasks. Caffeine increased the alertness and performance of the colds subjects to the same level as the healthy group and decaffeinated coffee also led to an improvement. These results suggest that drugs which increase alertness can remove the malaise associated with the common cold, and that increased stimulation of the sensory afferent nerves may also be beneficial.