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Alterations in brain tryptophan levels cause changes in brain serotonin synthesis, and this has been used to study the implication of altered serotonin levels in humans. In the acute tryptophan depletion (ATD) technique, subjects ingest a mixture of amino acids devoid of tryptophan. This results in a transient decline in tissue tryptophan and in brain serotonin. ATD can result in lower mood and increase in irritability or aggressive responding. The magnitude of the effect varies greatly depending on the susceptibility of the subject to lowered mood or aggressivity. Unlike ATD, tryptophan can be given chronically. Tryptophan is an antidepressant in mild to moderate depression and a small body of data suggests that it can also decrease aggression. Preliminary data indicate that tryptophan also increases dominant behavior during social interactions. Overall, studies manipulating tryptophan levels support the idea that low serotonin can predispose subjects to mood and impulse control disorders. Higher levels of serotonin may help to promote more constructive social interactions by decreasing aggression and increasing dominance. [Copyright &y& Elsevier]

Abstract: Bright light is used to treat winter depression and may also have positive effects on mood in some healthy individuals. However, there is little information on how bright light treatment influences social behavior. We performed a cross-over study in winter comparing the effects of morning bright light administration with placebo (exposure to negative ions) on mood and social behavior in 38 healthy people with mild to moderate seasonality. Each treatment was given for 21days with a washout period of 14days between treatments. An event-contingent recording assessment was used to measure mood, and social behavior along two axes, agreeable-quarrelsome and dominant–submissive, during each 21-day treatment period. During treatments, participants wore a combined light-sensor and accelerometer to test this method for adherence to light treatment self-administered at home. Data were analyzed using multilevel modeling. Bright light improved mood but increased quarrelsome behavior and decreased submissiveness. Data from the light monitor and accelerometer suggested that 21% of the participants did not adhere to bright light treatment; when this group was analyzed separately, there was no change in quarrelsomeness or mood. However, results for individuals who followed the procedure were similar to those reported for the whole sample. [Copyright &y& Elsevier]

Many studies have shown that having a meal together with others increases food intake. In contrast, the effects of having a meal on interactions with others have rarely been examined. More specifically, it is unknown if having a social interaction during a meal alters how people feel, behave, and perceive others. In the present study, 98 working individuals provided information on their everyday social interactions over a three-week period by filling in a form soon after each interaction. Record forms included items representing mood state, interpersonal behaviors, and perceptions of interaction partners. Participants also indicated whether interactions took place during a meal. Engaging in an interaction that involved eating a meal was associated with decreased alertness and, particularly in women, with increased pleasant affect, compared to interactions that did not involve eating a meal. Independently of this, during a meal participants reported fewer dominant and submissive behaviors and more agreeable behaviors, and also perceived interaction partners as more agreeable. These results were largely independent of contextual factors such as the gender and role of the primary social interaction partner, the presence of multiple partners, and the location of the interaction. Overall, social interactions during a meal were more positive in terms of how people felt, behaved, and perceived others. At the same time, agentic behaviors were reduced. These results suggest that shared meals are events in which affiliative bonds are strengthened in the context of weakened displays of hierarchy. [ABSTRACT FROM AUTHOR]

The ratio of the length of the second finger, or digit, to the fourth finger (2D:4D) is influenced by fetal exposure to androgens; a smaller ratio indicates greater androgen exposure. We used event contingent recording to investigate the relation between the 2D:4D ratio and social behavior. Participants completed multiple records of their behavior in events in naturalistic settings; records included information about situational features such as the gender of the person with whom the person was interacting. Men were more agreeable towards women than men; this effect was significantly greater in those with smaller 2D:4D ratios. Men with smaller 2D:4D ratios were also less quarrelsome towards women than towards men. The 2D:4D ratio did not influence social behavior in women. The hormonal environment in which the male fetal brain develops may influence adult social behavior in specific contexts. [ABSTRACT FROM AUTHOR]

Summary: Despite a large body of research in non-human primates, the relationship between naturalistic patterns of social behaviour and basal cortisol levels has been understudied in humans. The present study examined the relationship between patterns of interpersonal functioning and cortisol levels in 23 offspring of parents with bipolar disorder (BD), at high risk for the development of an affective disorder, and 22 offspring of parents with no affective disorder (controls) in late adolescence and young adulthood. Using event-contingent recording, participants rated their dominance, submissiveness, quarrelsomeness, and agreeableness in naturally occurring social interactions over 14 consecutive days and provided salivary cortisol twice daily in the afternoon over the same period. In the full sample, multilevel modelling analyses revealed that dominance was a significant positive predictor of afternoon basal cortisol levels, t (35) =2.58, p <0.05. Moreover, risk group (having a parent with BD or parents with no affective disorder) significantly interacted with mean levels of quarrelsomeness to predict afternoon cortisol levels, t (29) =2.06, p <0.05. Offspring of parents with BD who reported more frequent quarrelsome behaviours exhibited lower levels of afternoon cortisol relative to high-risk offspring reporting few quarrelsome behaviours and control offspring. The results are consistent with evidence that dominance is associated with high cortisol levels in an unstable environment, and suggest that quarrelsomeness among high risk youth contributes to altered hypothalamic–pituitary–adrenal activity. [ABSTRACT FROM AUTHOR]

Abstract: Background: Poor interpersonal functioning may represent a putative prodromal feature of major affective disorder. However, no studies have examined the naturalistic patterns of social behaviours among the offspring of parents with a major affective disorder. The present study assessed daily social interactions among 25 offspring of parents with bipolar disorder and 23 control participants in late adolescence and young adulthood. Methods: Using event-contingent recording procedures, interpersonal behaviours and perceptions were assessed along four scales (quarrelsomeness, agreeableness, dominance, and submissiveness) and were measured during specific social interactions over 14 days. Results: Multilevel modeling analyses revealed no group differences on any of the four scales, but gender by group interactions were was observed. High-risk males reported higher mean levels of quarrelsome behaviour and lower mean levels of agreeable behaviour than high-risk females, whereas low-risk males and females reported comparable levels of affiliative behaviours. High-risk participants reported more externalizing, but not internalizing, problems on the Achenbach Youth Self-Report Form than low-risk participants. Limitations: Although event-contingent recording reduces the self-report bias associated with self-report questionnaires, participants may have been biased in the selection of interactions they chose to record. Conclusions: Overall, the offspring of parents with BD, relative to controls, report no deficits in social functioning in the natural environment. However, high-risk youth displayed elevated externalizing problems and gender-specific patterns of social functioning that may precede the development of major affective disorder. [Copyright &y& Elsevier]

Background: Pharmacological evidence support that enhancement of serotonin (5-HT) neurotransmission is critical for treatment efficacy in obsessive-compulsive disorder (OCD). Surprisingly, acute tryptophan depletion (ATD), a procedure known to reduce 5-HT neurotransmission, carried out in remitted OCD patients on selective serotonin reuptake inhibitors (SSRIs) failed to worsen obsessive-compulsive (OC) symptoms. We hypothesized that the putative symptom exacerbation resulting from ATD would only be observed during symptom provocation but not at rest. Methods: Double-blind placebo-controlled ATD study conducted in 16 OCD patients with stable improvement under either SSRI (n = 8) or specialized cognitive behavior therapy alone (n = 8), coupled with gradual symptom provocation, performed 5 hours after drink ingestion. Results: Acute tryptophan depletion markedly reduced total and free plasma tryptophan levels but did not significantly increase obsessions or compulsions at rest or following symptom provocation. However, subjective distress in response to triggering situations was significantly higher during ATD; significant mood lowering was also present during ATD. Conclusions: These results are consistent with the view that relapses in OC core symptoms in remitted OCD patients may not depend solely on short-term changes in presynaptic 5-HT availability. In contrast to its apparent lack of effect on core OC symptoms, ATD affected the patient’s mood and distress level resulting from provocation. [Copyright &y& Elsevier]

Studies of bulimia nervosa (BN) often report decreased brain serotonin (5-hydroxytryptamine: 5-HT) activity. Across populations, impulsivity has been linked to reduced 5-HT activity, but compulsivity has been associated (at least inconsistently) with an increase. We therefore became interested in the association between behavioral-trait variations and 5-HT status in BN. In 56 bulimic and 29 non-bulimic women, we measured eating symptoms, personality traits, platelet paroxetine binding, and neuroendocrine responses following oral meta-chlorophenylpiperazine (m-CPP). Relative to normal eaters, bulimic women showed reduced density (Bmax) of platelet paroxetine-binding sites, blunted prolactin (PRL) responses following m-CPP, and (as a trend) lower basal PRL levels. However, after effects of binge–purge frequencies, body mass, and other extraneous factors were controlled, PRL levels at baseline and other moments in the serial sampling varied systematically with presence of impulsive and compulsive traits. PRL was generally low in BN, but ‘high-compulsive’/‘low-impulsive’ traits were associated with higher (normal-range) PRL values. Comparable trait-related variations were not observed on paroxetine-binding indices. Our findings suggest that 5-HT status in BN may correspond to impulsive or compulsive traits, and they encourage multidimensional modeling of the pathophysiological role of 5-HT in BN. [Copyright &y& Elsevier]

Given the putative role of serotonin in the modulation of smoking withdrawal and the central actions of nicotine, this study examined the affective and neuroelectric correlates of smoking abstinence and cigarette smoking following depletion of the serotonin precursor, tryptophan. In a randomized, double-blind two session (tryptophan depletion [TD] vs. nondepletion), placebo-controlled design, spectrally analyzed electroencephalogram (EEG), self-ratings of withdrawal symptoms and mood states were assessed in 18 male cigarette smokers before smoking abstinence, 5 h postsmoking abstinence and again following sham smoking and the smoking of one cigarette. Compared to a nutritionally balanced amino acid (AA) mixture containing tryptophan (i.e., placebo mixture), oral ingestion of a similar mixture devoid of tryptophan resulted in a 70% reduction of plasma tryptophan but failed to alter the appearance or reversal (by acute cigarette smoking) of withdrawal symptoms, negative mood states and increased slow wave EEG in male smokers deprived of cigarettes. These results, although not supporting a role for the serotonergic system in acute smoking and early smoking abstinence symptoms, are discussed in relation to the neuropharmacology of smoking behavior and suggestions for future work. [Copyright &y& Elsevier]