Acute Tryptophan Depletion Moja-De: A Method to Study Central Nervous Serotonin Function in Children and Adolescents

Serotonin (5-HT) is widely implicated as a key neurotransmitter relevant to a range of psychiatric disorders and psychological processes. The role of central nervous 5-HT function underlying these processes can be examined through serotonergic challenge methodologies. Acute tryptophan depletion (ATD) is a key challenge method whereby a diminished dietary intake of tryptophan-the amino acid precursor to brain 5-HT synthesis-results in temporary diminished central nervous 5-HT synthesis. While this particular methodology has been used in adult populations, it was only recently that modifications were made to enable the use of ATD in child and adolescent populations. Additionally, the Moja-De modification of the ATD challenge methodology has demonstrated benefits over other ATD techniques used previously. The aim of this protocol paper is to describe the ATD Moja-De methodology in detail, its benefits, as well as studies that have been conducted to validate the procedure in child and adolescent samples. The ATD Moja-De protocol provides a potential methodology for investigating the role of central nervous 5-HT via manipulation of brain tryptophan availability in human psychopathology from a developmental viewpoint.

Concurrent developmental course of sleep problems and emotional/behavioral problems in childhood and adolescence as reflected by the dysregulation profile

OBJECTIVES

Longitudinal data on the course and relationship of concurrent psychopathology in youth are scarce but are of need for better practical patient care and prevention. This study explores the course of (and relationships over time) between sleep problems and concurrent dimensional difficulties relating to anxiety/depression, attention deficiency, and aggressive behaviors in childhood and adolescence. The latter three may jointly form a broad syndrome, the dysregulation profile.

METHODS

Young people from the Raine Study, a large community cohort sample (N = 1625) were followed from age 5 to 17 years. Developmental courses of sleep problems and its concurrent regulatory difficulties were estimated separately and jointly.

RESULTS

The majority of adolescents reported low levels of problems and which appeared to be stable over time, while a small group (rates between 7.8% and 10.1%) reported enduring problematic developmental courses. Sleep problems and regulatory difficulties shared a strong association in their development over time (individual's probabilities of having the same courses, i.e. low-low and high-high, were between 89.8% and 92.3%). Furthermore, having persistent sleep problems over time was associated with an increased risk of having regulatory difficulties by approximately 10 times, and vice versa.

CONCLUSION

Findings from this study provide empirical evidence for a strong mutual association in the development of sleep problems and difficulties of dysregulation with emotion, cognition, and aggression. It may be suggested that a positive screening of one such psychopathological dimension should lead to a careful assessment, not only to reduce the problem in question but also to prevent the youth from further problems.

Moral Disengagement of Pure Bullies and Bully/Victims: Shared and Distinct Mechanisms

The vast majority of adolescents recognize that bullying is morally wrong, yet bullying remains a problem in secondary schools, indicating young people may disengage from their moral values to engage in bullying. But it is unclear whether the same mechanisms enabling moral disengagement are active for bully/victims (who both bully and are bullied) as for pure bullies (who are not targets of bullying). This study tested the hypotheses that mechanisms of moral disengagement, including blaming the victim and minimizing the impact of bullying, may operate differently in bully/victims compared to pure bullies. From a sample of 1895 students from grades 7-9 (50.6% female; 83.4% from English speaking homes), 1870 provided self-reports on bullying involvement and mechanisms of moral disengagement associated with bullying. Two cut-offs were compared for bullying involvement (as perpetrator and as target of bullying) during the previous school term: a conservative cut-off (every few weeks or more often) and a liberal cut-off (once-or-twice). Using the conservative cut-off, both pure bullies and bully/victims enlisted moral disengagement mechanisms to justify bullying more than did uninvolved students and pure victims, with no significant difference in scores on any of the moral disengagement scales between pure bullies and bully/victims. For the liberal cut-off, bully/victims reported lower overall moral disengagement scores than did pure bullies, and specifically less distortion of consequences, diffusion of responsibility, and euphemistic labeling. This study advances bullying research by extending the role of moral disengagement in bullying episodes beyond pure bullies to victims, both pure victims and bully/victims. Examination of specific moral disengagement mechanisms and the extent of involvement in bullying enabled a more nuanced differentiation between the bullying groups. These results will inform future interventions aimed at reducing the use of moral disengagement mechanisms that sustain bullying and victimization. Targeted interventions are needed to challenge specific moral disengagement mechanisms from the perspectives of pure bullies and bully/victims.

No detectable effects of acute tryptophan depletion on short-term immune system cytokine levels in healthy adults

Objectives: Recent research suggested an influence of diminished central nervous serotonin (5-HT) synthesis on the leptin axis via immunological mechanisms in healthy adult females. However, studies assessing immunological parameters in combination with dietary challenge techniques that impact brain 5-HT synthesis in humans are lacking.  Methods: In the present trial, a pilot analysis was conducted on data obtained in healthy adult humans receiving either different dietary acute tryptophan depletion (ATD) challenge or tryptophan (TRP)-balanced control conditions (BAL) to study the effects of reduced central nervous 5-HT synthesis on serum tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β) and IL-6 concentrations. The data of N = 35 healthy adults were analysed who were randomly subjected to one of the following two dietary conditions in a double-blind between-subject approach: (1) The Moja-De ATD challenge (ATD), or (2) TRP-balanced control condition for ATD Moja-De (BAL). Serum concentrations for the assessment of relevant parameters (TNF-α, IL-1β and IL-6) and relevant TRP-related characteristics after the respective challenge procedures were assessed at baseline (T0) and in hourly intervals after administration over a period of 6 h (T1-T6).  Results: The ATD condition did not result in significant changes to cytokine concentrations for the entire study sample, or in male and female subgroups. Depletion of CNS 5-HT via dietary TRP depletion appears to have no statistically significant short-term impact on cytokine concentrations in healthy adults.  Conclusions: Future research on immunological stressors in combination with challenge techniques will be of value in order to further disentangle the complex interplay between brain 5-HT synthesis and immunological pathways.

Serotonin and aggressive behaviour in children and adolescents: a systematic review

OBJECTIVE

The role of serotonin (5-HT) in human aggression has been the subject of a large number of studies, mostly with adults. Meta-analyses indicate a small but significant inverse relationship between central nervous 5-HT availability and aggression, but genetically informed studies suggest two pathways: one to reactive aggression and the other to proactive aggression.

METHOD

We conducted a systemic review on central nervous 5-HT function in children and adolescents, with attention to the function of aggression.

RESULTS

In total, 675 articles were screened for relevance, with 45 reviewed. These included blood assays (e.g. plasma, 5-HIAA; platelet 5-HTR_2A ), epigenetic studies, retrospective PET studies and 5-HT challenge paradigms (e.g. tryptophan depletion). Overall, findings were mixed, with support both for negative and for positive associations of central nervous 5-HT function with aggression in children and adolescents.

CONCLUSION

We propose factors that may be blurring the picture, including problems in the conceptualization and measurement of aggression in young people, the lack of prospective designs and the bias towards clinical samples of boys. Research needs to account for variance in the both motivation for and implementation of aggression, and look to the behavioural economics literature to consider the roles of reward, vengeance and self-control more clearly.

Using acute tryptophan depletion to investigate predictors of treatment response in adolescents with major depressive disorder: study protocol for a randomised controlled trial

Background

Selective serotonin reuptake inhibitors (SSRIs) are amongst the most prescribed antidepressants for adolescents with depressive symptoms and major depressive disorder. However, SSRIs have significant shortcomings as a first-line treatment considering that not all patients respond to these antidepressants. Amongst paediatric populations, meta-analyses indicate that up to approximately 40% of patients do not respond, and for those who do show benefit, there is substantial heterogeneity in response onset. The neurotransmitter serotonin (5-HT) plays a role in the clinical effectiveness and mechanisms of action of SSRIs. However, the exact and complete mechanism of action and reasons for the low response rate to SSRIs in some adolescent populations remains unknown.

Methods

To examine SSRI response and the role of 5-HT, this study will employ a randomised double-blind within subject, repeated measures design, recruiting adolescent patients with major depressive disorder. Participants will be subjected to acute tryptophan depletion (ATD) and the balanced control condition on two separate study days within a first study phase (Phase A), and the order in which these conditions (ATD/balanced control condition) occur will be random. This phase will be followed by Phase B, where participants will receive open label pharmacological treatment as usual with the SSRI fluoxetine and followed-up over a 12-week period.

Discussion

ATD is a neurodietary method typically used to investigate the impact of lowered brain 5-HT synthesis on mood and behaviour. The major hypothesis of this study is that ATD will be negatively associated with mood and cognitive functioning, therefore reflecting individual serotonergic sensitivity and related depressive symptoms. Additionally, we expect the aforementioned effects of ATD administration on mood to predict clinical improvement with regard to overall depressive symptomatology 12 weeks into SSRI treatment.

Trial registration

Australian and New Zealand Clinical Trials Registry (ANZCTR) ACTRN12616001561471. Registered on 11 November 2016.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-2791-4) contains supplementary material, which is available to authorized users.

Beyond the reactive-proactive dichotomy: Rage, revenge, reward, and recreational aggression predict early high school bully and bully/victim status

The role of reactive and proactive aggression in school bullying perpetration remains unclear. In this study, we explore the predictive value of an expanded model of aggression motives based on the Quadripartite Violence Typology (QVT), which distinguishes between motivational valence (appetitive or aversive) and recruitment of deliberative self-control to derive four classes of motives: Rage, Revenge, Reward, and Recreation. With a sample of 1,802 students from grades 7-9, we assessed aggression motives via self-report, along with self-report of bullying perpetration and victimization, which were used to assign students into categories of Pure Bully, Bully/Victim (B/V), Pure Victim, and Uninvolved. Two structural models were computed to examine the relationship between these four categories of bullying involvement and aggression motives, using conservative and liberal bullying cutoffs. As predicted, B/V status was more strongly related to Rage and Revenge motives. However, B/Vs had higher scores than Pure Bullies for almost all aggression motives, including Recreation. We discuss the implications of addressing Revenge and Recreation, as well as Reward and Rage (which map most clearly to proactive and reactive aggression, respectively) aggression motives, for bullying prevention and intervention strategies, especially among adolescents for whom extant bullying prevention strategies may be ineffective or counterproductive.

Does the Risk Outweigh the Benefits? Adolescent Responses to Completing Health Surveys

The aim of this study is to describe the self-reported experiences of adolescents in population-based samples when completing health-related surveys on topics with varying potential for evoking distress. Survey data were collected in three school-based studies of bullying behaviors (N = 1,771, 12-14 years), alcohol use (N = 823, 12, 15, and 17 years), and electronic image sharing (N = 274, 13 years). Between 5% and 15% of respondents reported being upset at survey completion, but at most 1.4% were entirely negative in their evaluation. Age was not associated with being upset, but younger adolescents were more likely to see benefit in participation. Although concurrent mental health symptoms increased the risk of being upset, this was mostly mitigated by perceived benefits from participation.

Effects of Dietary Acute Tryptophan Depletion (ATD) on NPY Serum Levels in Healthy Adult Humans Whilst Controlling for Methionine Supply-A Pilot Study

Central nervous serotonin (5-HT) can influence behaviour and neuropsychiatric disorders. Evidence from animal models suggest that lowered levels of neuropeptide Y (NPY) may have similar effects, although it is currently unknown whether decreased central nervous 5-HT impact NPY concentrations. Given that the production of NPY is dependent on the essential amino acid methionine (MET), it is imperative to account for the presence of MET in such investigations. Hence, this study sought to examine the effects of acute tryptophan depletion (ATD; a dietary procedure that temporarily lowers central nervous 5-HT synthesis) on serum concentrations of NPY, whilst using the potential renal acid load indicator (PRAL) to control for levels of MET. In a double-blind repeated measures design, 24 adult humans randomly received an AA-load lacking in TRP (ATD) on one occasion, and a balanced control mixture with TRP (BAL) on a second occasion, both with a PRAL of nearly 47.3 mEq of MET. Blood samples were obtained at 90, 180, and 240 min after each of the AA challenges. ATD, and therefore, diminished substrate availability for brain 5-HT synthesis did not lead to significant changes in serum NPY concentrations over time, compared to BAL, under an acute acidotic stimulus.

Nitrous oxide (N2O) and subsequent open-label SSRI treatment of adolescents with depression (NOTAD): study protocol for a randomised controlled trial

Background

The first line of pharmacological treatment for severe depressive disorders in young people is selective serotonin reuptake inhibitors (SSRIs). However, beneficial clinical effects are rarely observed before several weeks into treatment. Nitrous oxide (N₂O) has a long-standing safety record for pain relief and has been used in adults and young people. In adults with severe treatment-resistant depression, a single dose of N₂O had significant antidepressant effects, with maximum antidepressant effects observed 24 h after administration. However, the antidepressant effects of N₂O have never been investigated in adolescents with a confirmed diagnosis of depression in a prospective trial. The aims of this study are to (1) investigate whether a single inhaled N₂O administration leads to antidepressant effects in adolescents with depression at 24 h, (2) determine whether combined N₂O and SSRI administration (commenced after N₂O intervention) provides a clinically significant improvement in mood over and above the benefits from SSRI administration alone, and, (3) investigate whether the effect seen following N₂O administration can be used as a predictor of SSRI treatment response.

Methods/design

In this study, we will use a single-blind, randomised, placebo-controlled design. Patients aged between 12 and 17 years with major depressive disorder will be recruited. This study will consist of two phases: phase A and phase B. During phase A, participants will be randomised to receive either inhaled N₂O or placebo (air) for 1 h. In phase B, participants will receive open-label pharmacological treatment with the SSRI fluoxetine and will be followed over a 12-week period. Participants will undertake mood assessments at 2 and 24 h after N₂O or placebo administration (phase A) and weekly during the 12-week follow up in phase B.

Discussion

We expect an antidepressant effect from a single dose of inhaled N₂O compared with placebo at 24 h after administration. Additionally, we expect that subjects treated with N₂O will also show greater improvements than the placebo group after 6 and 12 weeks into fluoxetine treatment because of potential additive antidepressant effects. Such findings would be of clinical importance because currently children and adolescents often do not experience any symptom alleviation for several weeks following the initiation of SSRIs.

Trial registration

Australian and New Zealand Clinical Trials Registry, ACTRN12616001568404. Registered on 14 November 2016.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-2342-4) contains supplementary material, which is available to authorized users.

Functional connectivity of the vigilant-attention network in children and adolescents with attention-deficit/hyperactivity disorder

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ADHD affects functional connectivity in a brain network for vigilant attention (VA).

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First evidence showing the VA network is intrinsically coupled in older children.

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ADHD patients showed less consistent network connectivity, forming 2 subnetworks.

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Lower network integrity in ADHD is due to both weaker and stronger connections.

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Aberrant connectivity between several regions is linked to ADHD symptomatology.

The ability to maintain attention to simple tasks (i.e., vigilant attention, VA) is often impaired in attention-deficit/hyperactivity disorder (ADHD), but the underlying pathophysiological mechanisms at the brain network level are not clear yet. We therefore investigated ADHD-related differences in resting-state functional connectivity within a meta-analytically defined brain network of 14 distinct regions subserving VA (comprising 91 connections in total), as well as the association of connectivity with markers of behavioural dysfunction in 17 children (age range: 9–14 years) with a diagnosis of ADHD and 21 age-matched neurotypical controls. Our analyses revealed selective, rather than global, differences in the intrinsic coupling between nodes of the VA-related brain network in children with ADHD, relative to controls. In particular, ADHD patients showed substantially diminished intrinsic coupling for 7 connections and increased coupling for 4 connections, with many differences involving connectivity with the anterior insula. Moreover, connectivity strength of several aberrant connections was found to be associated with core aspects of ADHD symptomatology, such as poor attention, difficulties with social functioning, and impaired cognitive control, attesting to the behavioural relevance of specific connectivity differences observed in the resting state.

Disentangling functions of online aggression: The Cyber-Aggression Typology Questionnaire (CATQ)

Aggression in online contexts has received much attention over the last decade, yet there is a need for measures identifying the proximal psychological drivers of cyber-aggressive behavior. The purpose of this study was to present data on the newly developed Cyber-Aggression Typology Questionnaire (CATQ) designed to distinguish between four distinct types of cyber-aggression on dimensions of motivational valence and self-control. A sample 314 undergraduate students participated in the study. The results confirmed the predicted four-factor structure providing evidence for distinct and independent impulsive-aversive, controlled-aversive, impulsive-appetitive, and controlled-appetitive cyber-aggression types. Further analyses with the Berlin Cyberbullying Questionnaire, Reactive Proactive Aggression Questionnaire, and the Behavior Inhibition and Activation Systems Scale provide support for convergent and divergent validity. Understanding the motivations facilitating cyber-aggressive behavior could aid researchers in the development of new prevention and intervention strategies that focus on individual differences in maladaptive proximal drivers of aggression. Aggr. Behav. 43:74-84, 2017. © 2016 Wiley Periodicals, Inc.

Developmental Trajectories of Sleep Problems from Childhood to Adolescence Both Predict and Are Predicted by Emotional and Behavioral Problems

Although the prevalence rates of sleep disorders at different stages of childhood and adolescence have been well established, little is known about the developmental course of general sleep problems. This also holds true for the bidirectional relationship between sleep problems and emotional as well as behavioral difficulties. This longitudinal study investigated the general pattern and the latent trajectory classes of general sleep problems from a large community sample aged 5–14 years. In addition, this study examined the predictive value of emotional/behavioral difficulties (i.e., anxiety/depression, attention problems, and aggressive behavior) on sleep problems latent trajectory classes, and vice-versa. Participants (N = 1993) were drawn from a birth cohort of Western Australian children born between 1989 and 1991 who were followed until 14 years of age. Sleep problems were assessed at ages 5, 8, 10, and 14, respectively, whereas anxiety/depression, attention problems, and aggressive behavior were assessed at ages 5 and 17 years. Latent growth curve modeling revealed a decline in an overall pattern of sleep problems during the observed 10-year period. Anxiety/depression was the only baseline factor that predicted the longitudinal course of sleep problems from ages 5 to 14 years, with anxious and depressed participants showing faster decreasing patterns of sleep problems over time than those without anxiety or depression. Growth mixture modeling identified two classes of sleep problem trajectories: Normal Sleepers (89.4%) and Troubled Sleepers (10.6%). Gender was randomly distributed between these groups. Childhood attention problems, aggressive behavior, and the interaction between gender and anxiety/depression were significantly predictive of membership in the group of Troubled Sleepers. Group membership in Troubled Sleepers was associated with higher probability of having attention problems and aggressive behavior in mid-adolescence. Boys and girls with behavioral difficulties, and girls with emotional difficulties were at increased risk of having sleep problems during later childhood and adolescence. Developmental trajectories of sleep problems were also predictive of behavioral difficulties in later life. Findings from this study provide empirical evidence for the heterogeneity of sleep problems and their development, and emphasize the importance of understanding sleep problems and their relationship to children and adolescents’ mental health.

Bullying prevalence across contexts: a meta-analysis measuring cyber and traditional bullying

Bullying involvement in any form can have lasting physical and emotional consequences for adolescents. For programs and policies to best safeguard youth, it is important to understand prevalence of bullying across cyber and traditional contexts. We conducted a thorough review of the literature and identified 80 studies that reported corresponding prevalence rates for cyber and traditional bullying and/or aggression in adolescents. Weighted mean effect sizes were calculated, and measurement features were entered as moderators to explain variation in prevalence rates and in traditional-cyber correlations within the sample of studies. Prevalence rates for cyber bullying were lower than for traditional bullying, and cyber and traditional bullying were highly correlated. A number of measurement features moderated variability in bullying prevalence; whereas a focus on traditional relational aggression increased correlations between cyber and traditional aggressions. In our meta-analytic review, traditional bullying was twice as common as cyber bullying. Cyber and traditional bullying were also highly correlated, suggesting that polyaggression involvement should be a primary target for interventions and policy. Results of moderation analyses highlight the need for greater consensus in measurement approaches for both cyber and traditional bullying.

Bullying prevalence across contexts: a meta-analysis measuring cyber and traditional bullying

Bullying involvement in any form can have lasting physical and emotional consequences for adolescents. For programs and policies to best safeguard youth, it is important to understand prevalence of bullying across cyber and traditional contexts. We conducted a thorough review of the literature and identified 80 studies that reported corresponding prevalence rates for cyber and traditional bullying and/or aggression in adolescents. Weighted mean effect sizes were calculated, and measurement features were entered as moderators to explain variation in prevalence rates and in traditional-cyber correlations within the sample of studies. Prevalence rates for cyber bullying were lower than for traditional bullying, and cyber and traditional bullying were highly correlated. A number of measurement features moderated variability in bullying prevalence; whereas a focus on traditional relational aggression increased correlations between cyber and traditional aggressions. In our meta-analytic review, traditional bullying was twice as common as cyber bullying. Cyber and traditional bullying were also highly correlated, suggesting that polyaggression involvement should be a primary target for interventions and policy. Results of moderation analyses highlight the need for greater consensus in measurement approaches for both cyber and traditional bullying.

Reactive aggression and peer victimization from pre-kindergarten to first grade: accounting for hyperactivity and teacher-child conflict

BACKGROUND

The role of reactive aggression in the development of peer victimization remains unclear due in part to a failure to account for confounding problems of behavioural undercontrol (e.g., hyperactivity). As well, the school social context has rarely been examined to see whether these risks are mediated by relationships with teachers.

AIMS

This study tests the prospective relations between reactive aggression, hyperactivity, victimization, and teacher-child (T-C) relationship, to determine whether conflict mediates the relationships between externalizing problems and victimization.

SAMPLE

A sample of 1,114 Australian students were followed from pre-kindergarten through first grade.

METHODS

Cross-lagged path analyses were conducted, with comparison of gender-moderating models and autocorrelation models. Full-information maximum likelihood was deployed to account for missingness.

RESULTS

Best fitting models found that the relationship of early externalizing problems to later victimization was mediated by T-C conflict. No evidence of victimization increasing externalizing problems nor gender differences were observed. T-C conflict in kindergarten predicted subsequent increases in victimization, reactive aggression, and hyperactivity.

CONCLUSIONS

Understanding the processes whereby externalizing problems confer risk of victimization involves understanding the whole social context of classrooms, including relationships with teachers. Finer-grained research is needed to better understand how peer dynamics may be influenced by observation of T-C relationships. Pre-service teacher education needs to ensure a focus on the potential social impact of teacher's relationships with students.

Young children's social information processing: Family antecedents and behavioral correlates

Little research has examined whether social information processing (SIP) measures from early childhood predict externalizing problems beyond the shared association with familial risk markers. In the present study, family antecedents and first-grade externalizing behaviors were studied in relation to preschool and 1st-grade SIP using data from the U.S. National Institute for Child Health and Human Development Study of Early Child Care (N=1,364). A subgroup of low-risk children reported only benign attributions in preschool and had few externalizing problems in 1st grade according to both teacher and mother reports. After controlling for gender and cognitive functioning, the authors found that maternal education and authoritarian attitudes were key predictors of this "Pollyanna preschooler" status and of SIP in 1st grade. However, small effect sizes for SIP variables underscore the need for new approaches to measurement and for further research on moderators of the link between SIP and children's behavior.