Loneliness, HPA stress reactivity and social threat sensitivity: Analyzing naturalistic social challenges.

Loneliness has been linked to poor health through an increased activation of threat surveillance mechanisms, such as the hypothalamic-pituitary-adrenal axis (HPA). The socio-cognitive model (Cacioppo & Hawley) proposes that lonely people have an increased social threat sensitivity which activates the HPA axis. The current study examined the impact of loneliness on HPA stress reactivity and social threat sensitivity in response to naturally occurring social challenges. Participants (N = 45) were prospective undergraduates attending a 3-day university preparation programme over the summer, prior to commencing their university studies. Cortisol levels and perceived stress were measured before and after an ice breaker session on Day 1 and a lecture session on Day 3. Social threat sensitivity was also measured on the first and third day. When meeting unfamiliar peers in the ice breaker session, HPA stress reactivity was evident, but it was not markedly different in those who reported high levels of loneliness than those with low levels. The high loneliness group had higher levels of perceived stress and increased social threat sensitivity than the low loneliness group on both testing days. The findings show partial support for the socio-cognitive model of loneliness because increased threat sensitivity was demonstrated in the high loneliness group. The findings indicate that lonely people do not respond in a physiologically different way to specific social challenges, but they typically report higher social threat sensitivity and higher perceived stress than their non-lonely peers.

Exploring the Association between Alzheimer's Disease, Oral Health, Microbial Endocrinology and Nutrition.

Longitudinal monitoring of patients suggests a causal link between chronic periodontitis and the development of Alzheimer's disease (AD). However, the explanation of how periodontitis can lead to dementia remains unclear. A working hypothesis links extrinsic inflammation as a secondary cause of AD. This hypothesis suggests a compromised oral hygiene leads to a dysbiotic oral microbiome whereby Porphyromonas gingivalis, a keystone periodontal pathogen, with its companion species, orchestrates immune subversion in the host. Brushing and chewing on teeth supported by already injured soft tissues leads to bacteremias. As a result, a persistent systemic inflammatory response develops to periodontal pathogens. The pathogens, and the host's inflammatory response, subsequently lead to the initiation and progression of multiple metabolic and inflammatory co-morbidities, including AD. Insufficient levels of essential micronutrients can lead to microbial dysbiosis through the growth of periodontal pathogens such as demonstrated for P. gingivalis under low hemin bioavailability. An individual's diet also defines the consortium of microbial communities that take up residency in the oral and gastrointestinal (GI) tract microbiomes. Their imbalance can lead to behavioral changes. For example, probiotics enriched in Lactobacillus genus of bacteria, when ingested, exert some anti-inflammatory influence through common host/bacterial neurochemicals, both locally, and through sensory signaling back to the brain. Early life dietary behaviors may cause an imbalance in the host/microbial endocrinology through a dietary intake incompatible with a healthy GI tract microbiome later in life. This imbalance in host/microbial endocrinology may have a lasting impact on mental health. This observation opens up an opportunity to explore the mechanisms, which may underlie the previously detected relationship between diet, oral/GI microbial communities, to anxiety, cognition and sleep patterns. This review suggests healthy diet based interventions that together with improved life style/behavioral changes may reduce and/or delay the incidence of AD.

Prospective memory deficits in illicit polydrug users are associated with the average long-term typical dose of ecstasy typically consumed in a single session.

RATIONALE: Neuroimaging evidence suggests that ecstasy-related reductions in SERT densities relate more closely to the number of tablets typically consumed per session rather than estimated total lifetime use. To better understand the basis of drug related deficits in prospective memory (p.m.) we explored the association between p.m. and average long-term typical dose and long-term frequency of use. METHOD: Study 1: Sixty-five ecstasy/polydrug users and 85 nonecstasy users completed an event-based, a short-term and a long-term time-based p.m. task. Study 2: Study 1 data were merged with outcomes on the same p.m. measures from a previous study creating a combined sample of 103 ecstasy/polydrug users, 38 cannabis-only users, and 65 nonusers of illicit drugs. RESULTS: Study 1: Ecstasy/polydrug users had significant impairments on all p.m. outcomes compared with nonecstasy users. Study 2: Ecstasy/polydrug users were impaired in event-based p.m. compared with both other groups and in long-term time-based p.m. compared with nonillicit drug users. Both drug using groups did worse on the short-term time-based p.m. task compared with nonusers. Higher long-term average typical dose of ecstasy was associated with poorer performance on the event and short-term time-based p.m. tasks and accounted for unique variance in the two p.m. measures over and above the variance associated with cannabis and cocaine use. CONCLUSIONS: The typical ecstasy dose consumed in a single session is an important predictor of p.m. impairments with higher doses reflecting increasing tolerance giving rise to greater p.m. impairment.

Stress reactivity and cognitive performance in a simulated firefighting emergency.

BACKGROUND: During emergencies maladaptive behavior can reduce survival. This study compared the effects of a basic firefighter training course on 21 volunteers (with no firefighting experience) with age and gender-matched controls. METHODS: Stress reactivity (salivary cortisol and anxiety) were monitored across the course: day 1 (classroom), day 2 (physical equipment training), and day 3 (simulated fire emergency). Cognitive performance (visual attention, declarative and working memory) considered important in surviving a fire emergency were measured immediately post-training or after a 20-min delay. RESULTS: Prior to threat subjects showed an anticipatory cortisol increase but no corresponding increase in self-reported anxiety. On day 3 cortisol was higher in firefighters tested immediately after (10.37 nmol x L(-1) and 20 min after training (7.20 nmol L(-1)) compared to controls (3.13 nmol x L(-1)). Differences in cognitive performance were observed post-threat, with impairments in visual declarative memory in the firefighting subjects tested immediately, and working memory impairments observed in those tested after a 20-min delay. CONCLUSIONS: Cognitive impairments were found following a simulated emergency and could explain maladaptive responses observed during real fires. Moreover, the results suggest the type of cognitive impairments observed may be time dependent, with different cognitive difficulties becoming evident at different times following an emergency.

Loneliness trajectories from middle childhood to pre-adolescence: impact on perceived health and sleep disturbance.

The current study is the first to examine the association between chronic loneliness and perceived health, school absence due to illness, sleep duration and disturbance, in a sample of pre-adolescents (N = 209). Loneliness was measured in three collection waves that were 18 months apart and covered the ages 8-11 years. Using growth mixture modeling, two groups were identified with discrete growth patterns of loneliness: (a) relatively high, reducing loneliness (48%), and (b) low, stable loneliness (52%). At age 11 years, those in the relatively high, reducing lonely group reported higher levels of depressive symptoms, poorer general health, took longer to get to sleep, and had greater sleep disturbance than children in the low, stable loneliness group. These findings suggest that there may be long-term health effects of experiencing high loneliness in middle childhood, even when loneliness levels reduce to normal levels at pre-adolescence.

Effects of ecstasy/polydrug use on memory for associative information.

RATIONALE: Associative learning underpins behaviours that are fundamental to the everyday functioning of the individual. Evidence pointing to learning deficits in recreational drug users merits further examination. OBJECTIVES: A word pair learning task was administered to examine associative learning processes in ecstasy/polydrug users. METHODS: After assignment to either single or divided attention conditions, 44 ecstasy/polydrug users and 48 non-users were presented with 80 word pairs at encoding. Following this, four types of stimuli were presented at the recognition phase: the words as originally paired (old pairs), previously presented words in different pairings (conjunction pairs), old words paired with new words, and pairs of new words (not presented previously). The task was to identify which of the stimuli were intact old pairs. RESULTS: Ecstasy/ploydrug users produced significantly more false-positive responses overall compared to non-users. Increased long-term frequency of ecstasy use was positively associated with the propensity to produce false-positive responses. It was also associated with a more liberal signal detection theory decision criterion value. Measures of long term and recent cannabis use were also associated with these same word pair learning outcome measures. Conjunction word pairs, irrespective of drug use, generated the highest level of false-positive responses and significantly more false-positive responses were made in the divided attention condition compared to the single attention condition. CONCLUSIONS: Overall, the results suggest that long-term ecstasy exposure may induce a deficit in associative learning and this may be in part a consequence of users adopting a more liberal decision criterion value.

The effect of energy drinks on cortisol levels, cognition and mood during a fire-fighting exercise.

RATIONALE: Acute stress has been associated with changes in cognitive performance and mood, and these have been in part associated with stress-related increased release of cortisol. Both glucose and caffeine consumed in isolation have been shown to moderate cortisol response and affect cognitive performance and affect mood; however, there has been very little research into their behavioural and physiological effects when taken in combination. The aim of this study was to assess the effect of the two substances in combination under stressful and physically demanding conditions (fire-fighting training) on cognition, mood and cortisol release. METHODS: Using a double-blind, mixed measures design, 81 participants were administered a 330-ml drink containing either (1) 50 g glucose and 40 mg caffeine, (2) 10.25 g of fructose/glucose and 80 mg caffeine or a placebo drink and tested across a range of cognitive tasks, mood and physiological measures. RESULTS: The results showed an increase in grip strength and improved memory performance after ingestion of the drink containing 50 g glucose and 40 mg caffeine, and both active drinks resulted in improved performance on the information-processing task compared to the placebo. In terms of mood effects, the drink containing 50 g glucose and 40 mg caffeine led to a reduction in anxiety and significantly reduced self-reported levels of stress following the fire-fighter training. CONCLUSIONS: Based on the results of this study, in situations of stress combined with physical performance, administration of an energy drink containing glucose and caffeine might be an easy to implement and cost effective way to maintain mental performance levels and to ameliorate the negative effects of stress on mood.

The effect of mood-context on visual recognition and recall memory.

Although it is widely known that memory is enhanced when encoding and retrieval occur in the same state, the impact of elevated stress/arousal is less understood. This study explores mood-dependent memory's effects on visual recognition and recall of material memorized either in a neutral mood or under higher stress/arousal levels. Participants' (N = 60) recognition and recall were assessed while they experienced either the same o a mismatched mood at retrieval. The results suggested that both visual recognition and recall memory were higher when participants experienced the same mood at encoding and retrieval compared with those who experienced a mismatch in mood context between encoding and retrieval. These findings offer support for a mood dependency effect on both the recognition and recall of visual information.