Effects of dietary omega-3 intake on vigilant attention and resting-state functional connectivity in neurotypical children and adolescents.

BACKGROUND: Vigilant Attention (VA) is a critical cognitive function allowing to maintain our attention, particularly in redundant or intellectually unchallenging situations. Evidence has shown that, as the brain develops, VA abilities rapidly improve throughout childhood and adolescence. Dietary omega-3 polyunsaturated fats (PUFA), playing a critical role for proper brain development and maturation of cortical regions, may contribute to variations in VA abilities. OBJECTIVE: The present study investigated the effect of dietary omega-3 PUFA intake (docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)) on resting-state functional connectivity (rsFC) of a meta-analytically defined VA network in 24 neurotypical children and adolescents (7.3-17.2 years) from the Healthy Brain Network databank. METHODS: Functional MRI and phenotypical information were collected from the Healthy Brain Network databank. Intake of omega-3 DHA and EPA was assessed using a food frequency questionnaire and was adjusted for total calorie intake. Out of scanner VA-related performance was assessed using the VA condition of the Adaptive Cognitive Evaluation tool. RESULTS: Overall, reported intake of omega-3 PUFA was not significantly associated with VA-related performance. Furthermore, energy-adjusted omega-3 intake was not significantly correlated with rsFC within the VA network. A complementary whole-brain analysis revealed that energy-adjusted omega-3 intake was correlated with decreased rsFC between parieto-occipital brain regions. CONCLUSION: The present study was not able to detect a relationship between dietary omega-3 and rsFC or VA performance.

Age-related resting-state functional connectivity of the Vigilant Attention network in children and adolescents.

The development of Vigilant Attention (VA), the ability to focus and maintain our attention to repetitive and cognitively unchallenging tasks over time, has been investigated for more than a decade. The development of this critical executive function across the lifespan has been characterised by a rapid improvement in VA performance throughout childhood and adolescence, a steady improvement in adulthood and a slow decline in older adulthood. However, the development of the neural correlates of VA in children and adolescents remains poorly understood. Using a cross-sectional design, the present study used a meta-analytically defined VA network in children and adolescents to explore the developmental trend of the resting-state functional connectivity (rsFC) within the VA network across two independent cohorts. The results showed a linear and non-linear decrease of rsFC between the left and right VA brain regions across age. However, the results could not be reproduced in the replication cohort, potentially due to a smaller sample size. Based on previous findings from behavioural studies, the present findings suggest that changes in rsFC may underlie a developmental shift in cognitive strategies in neurotypical children and adolescents.

Latest guidelines for the management of the anxiety disorders - a report from The International Anxiety Disorders Society Conference, Melbourne 2014.

OBJECTIVE: The International Anxiety Disorders Society Conference, held in Melbourne in November 2014, enabled key researchers from Australia and internationally to interact with mental health practitioners with an interest in clinical anxiety disorders. The proceedings of previous conferences in 2006 and 2011 formed the basis of two well-received textbooks on anxiety disorders; this time we have taken up the invitation to publish the proceedings as articles in this issue of Australasian Psychiatry. At the end of the first day of the conference a lecture and linked international expert panel explored the topic of guidelines for the management of the anxiety disorders in conjunction with an engaged audience for 90 minutes - key elements of this discussion are presented here. CONCLUSIONS: Guidelines for anxiety disorder management should be applied with caution in clinical practice settings.

Systematic review and network meta-analysis of agomelatine for the treatment of generalized anxiety disorder in adult patients.

This systematic literature review aimed to assess the efficacy and tolerability of agomelatine versus approved medications for the treatment of generalized anxiety disorder (GAD) in adult patients. We selected randomized controlled trials on various medications used to treat GAD in adult patients. An existing systematic literature review (Kong et al., 2020) was used to identify relevant studies published before 2020. Outcomes of remission and discontinuation due to adverse events (AEs) were analyzed, following a random-effects network meta-analysis approach. Of 25 identified studies, 20 and 22 studies were included in the network meta-analysis for studying the remission and discontinuation (due to AEs) outcomes, respectively. A statistically significant difference in the remission rate was observed between agomelatine and pregabalin [odds ratio (OR), 2.22; 95% confidence interval (CI), 1.19-4.21]. For the other comparators, the results were nonsignificant; however, all the point estimates were in favor of agomelatine. Similarly, for discontinuation because of AEs, the point estimates leaned consistently toward agomelatine suggesting its higher tolerability. The probabilities of agomelatine having the highest remission rate and lowest discontinuation (due to AEs) rate were 67% and 68%, respectively. Based on its demonstrated effectiveness and tolerability, agomelatine can be considered as a drug of choice for the treatment of GAD.

The role of flumazenil in generalised anxiety disorder: a pilot naturalistic open-label study with a focus on treatment resistance.

Background: Anxiety disorders are highly prevalent and chronic disorders with treatment resistance to current pharmacotherapies occurring in approximately one in three patients. It has been postulated that flumazenil (FMZ) is efficacious in the management of anxiety disorders via the removal of α4ß2δ gamma-aminobutyric acid A receptors. Objective: To assess the safety and feasibility of continuous low-dose FMZ infusions for the management of generalised anxiety disorder (GAD) and collect preliminary efficacy data. Design: Uncontrolled, open-label pilot study. Method: Participants had a primary diagnosis of generalised anxiety disorder (GAD) and received two consecutive subcutaneous continuous low-dose FMZ infusions. Each infusion contained 16 mg of FMZ and was delivered over 96 ± 19.2 h. The total dose of FMZ delivered was 32 mg over approximately 8 days. Sodium valproate was given to participants at risk of seizure. The primary outcome was the change in stress and anxiety subscale scores on the Depression Anxiety Stress Scale-21 between baseline, day 8, and day 28. Results: Nine participants with a primary diagnosis of GAD were treated with subcutaneous continuous low-dose FMZ infusions; seven participants met the criteria for treatment resistance. There was a significant decrease in anxiety and stress between baseline and day 8 and baseline and day 28. There was also a significant improvement in subjective sleep quality from baseline to day 28 measured by the Jenkins Sleep Scale. No serious adverse events occurred. Conclusion: This study presents preliminary results for subcutaneous continuous low-dose FMZ's effectiveness and safety in GAD. The findings suggest that it is a safe, well-tolerated, and feasible treatment option in this group of patients. Future randomised control trials are needed in this field to determine the efficacy of this treatment.

Utility of pharmacogenetic testing to optimise antidepressant pharmacotherapy in youth: a narrative literature review.

Pharmacogenetics (PGx) is the study and application of how interindividual differences in our genomes can influence drug responses. By evaluating individuals' genetic variability in genes related to drug metabolism, PGx testing has the capabilities to individualise primary care and build a safer drug prescription model than the current "one-size-fits-all" approach. In particular, the use of PGx testing in psychiatry has shown promising evidence in improving drug efficacy as well as reducing toxicity and adverse drug reactions. Despite randomised controlled trials demonstrating an evidence base for its use, there are still numerous barriers impeding its implementation. This review paper will discuss the management of mental health conditions with PGx-guided treatment with a strong focus on youth mental illness. PGx testing in clinical practice, the concerns for its implementation in youth psychiatry, and some of the barriers inhibiting its integration in clinical healthcare will also be discussed. Overall, this paper provides a comprehensive review of the current state of knowledge and application for PGx in psychiatry and summarises the capabilities of genetic information to personalising medicine for the treatment of mental ill-health in youth.

Long-Term Management of Generalised Anxiety Disorder with Low-Dose Continuous Infusions of Flumazenil: A Case Series.

BACKGROUND: Generalised anxiety disorder (GAD) is a common anxiety disorder associated with social and occupational impairment. Recently, a theory was postulated that dysfunctional gamma aminobutyric acid type A receptors (GABAA) are implicated in anxiety symptomology, which could be corrected by flumazenil, an antagonist at the benzodiazepine binding site on the GABAA receptor. METHOD: Participants had a primary diagnosis of GAD and were treated initially with an eight-day continuous low-dose flumazenil infusion (total 32 mg at a rate of 4 mg/24 h). Some participants were re-treated with a further four- or eight-day infusion. Treatment response was measured as a 50% reduction in anxiety or stress scores on the Depression Anxiety Stress Scale-21 (DASS-21). Remission was measured as scores ≤3 or ≤7 on the anxiety and stress subscales of the DASS-21, respectively. RESULTS: Eight cases are reported. All cases met the criteria for treatment response on the anxiety and stress subscale of the DASS-21. Remission was achieved in seven participants on the anxiety subscale and in five on the stress subscale. No changes in hepatic, renal, or haematological function were likely attributed to flumazenil. CONCLUSION: Data suggest that low-dose continuous flumazenil infusion manages GAD symptoms and is safe. Although these results are promising, future randomised control trials are required to confirm these results.

Nabilone Impairs Spatial and Verbal Working Memory in Healthy Volunteers.

Background: Memory impairments and psychosis-like experiences can be adverse effects of cannabis use. However, reports on the cognitive impact of cannabis use are not consistent. There are also limited studies on the psychotomimetic effects of cannabinoid compounds to reveal the association between cannabis and psychosis. Therefore, we investigated the effect of acute cannabinoid intoxication on verbal working memory (VWM) and spatial working memory (SWM) following oral doses of the synthetic cannabinoid agonist, nabilone (1-2 mg, oral). We further investigated the effect of nabilone on psychosis-like experiences (schizotypy scores) and associations of schizotypy with VWM and SWM. Methods: Healthy participants (n=28) completed spatial and digit span tasks across different delay conditions (0, 6, 12, and 18 sec) after receiving nabilone (1-2 mg, PO) or placebo in a randomized, double-blind, counterbalanced, crossover manner. A subset of participants completed a short battery of schizotypy measures (n=25). Results: Nabilone impaired VWM (p=0.03, weak effect size η2=0.02) and SWM (p=0.00016, η2=0.08). Nabilone did not significantly change overall schizotypy scores. Schizotypy scores were negatively correlated with working memory (WM) averaged across all delays and both modalities, under placebo (ρ=-0.41, p=0.04). In addition, there were significant negative correlations between occasions of cannabis use and overall WM averaged scores across drug treatments (ρ=-0.49, p=0.007) and under placebo (ρ=-0.45, p=0.004). The results showed that the drug effect in the less frequent cannabis users was more pronounced on the SWM (p<0.01) and VWM (p<0.01), whereas there appeared to be little drug effect in the frequent cannabis users. Conclusion: Low doses of synthetic cannabinoid impaired SWM and VWM, indicating that exogenous activation of the cannabinoid system influences cognitive performance. Further, the results replicated previous findings that schizotypy is correlated with deficits in WM. Clinical Trial Registry Name: Nabilone and caffeine effects on the perceptions of visually, auditory, tactile and multimodal illusions in healthy volunteers. Clinical Trial Registration Number: CT-2018-CTN-02561 (Therapeutic Goods Administration Clinical Trial Registry) and ACTRN12618001292268 (The Australian New Zealand Clinical Trials Registry).

Meta-analysis of the neural correlates of vigilant attention in children and adolescents.

Vigilant Attention (VA), defined as the ability to maintain attention to cognitively unchallenging activities over a prolonged period of time, is critical to support higher cognitive functions and many behaviours in our everyday life. Evidence has shown that VA rapidly improves throughout childhood and adolescence until young adulthood and tends to decline in older adulthood. Although neuroimaging studies have extensively investigated this cognitive function in adults, the neural correlates of VA in neurotypical children and adolescents remain unclear. The current meta-analysis reviewed and examined functional neuroimaging studies in paediatric populations that used behavioural tasks involving VA. The selected studies (N = 25) were analyzed using the activation likelihood estimation method. Findings showed convergence of activation in mainly right-lateralized brain areas, including dorsomedial frontal cortex and parieto-temporal areas, and are consistent with previous literature on the neural correlates of VA. Results are discussed in terms of their functional and developmental implications for VA in children and adolescents.

Antidepressant-induced jitteriness/anxiety syndrome: systematic review.

BACKGROUND: Early worsening of anxiety, agitation and irritability are thought to be common among people commencing antidepressants, especially for anxiety disorders. This phenomenon, which may be termed jitteriness/anxiety syndrome, is cited as an explanation for early treatment failure and caution in using selective serotonin reuptake inhibitors (SSRIs). However, we believe that it is inconsistently defined and that robust evidence to support the phenomenon is lacking. AIMS: To review systematically all evidence relating to jitteriness/anxiety syndrome to identify: constituent symptoms; medications implicated; disorders in which it was reported; incidence; time course; management strategies; relationship of this syndrome to therapeutic response; distinction between syndrome and akathisia; relationship between syndrome and suicide; and genetic predispositions. METHOD: A systematic search identified articles and these were included in the review if they addressed one of the above aspects of jitteriness/anxiety syndrome. RESULTS: Of 245 articles identified, 107 articles were included for review. No validated rating scales for jitteriness/anxiety syndrome were identified. There was no robust evidence that the incidence differed between SSRIs and tricyclic antidepressants, or that there was a higher incidence in anxiety disorders. Published incidence rates varied widely from 4 to 65% of people commencing antidepressant treatment. Common treatment strategies for this syndrome included a slower titration of antidepressant and the addition of benzodiazepines. Conclusive evidence for the efficacy of these strategies is lacking. There was conflicting and inconclusive evidence as to whether the emergence of this syndrome had a predictive value on the response to treatment. It appears to be a separate syndrome from akathisia, but evidence for this assertion was limited. The effect of jitteriness/anxiety syndrome on suicide rates has not been evaluated. Three studies examined genetic variations and side-effects from treatment, but none was specifically designed to assess jitteriness/anxiety syndrome. CONCLUSIONS: Jitteriness/anxiety syndrome remains poorly characterised. Despite this, clinicians' perception of this syndrome influences prescribing and it is cited to support postulated mechanisms of drug action. We recommend systematised evaluation of side-effects at earlier time points in antidepressant trials to further elucidate this clinically important syndrome.

Efficacy of a standardised saffron extract (affron®) as an add-on to antidepressant medication for the treatment of persistent depressive symptoms in adults: A randomised, double-blind, placebo-controlled study.

BACKGROUND: As a stand-alone intervention, saffron has efficacy for the treatment of mild-to-moderate depression. However, research as an adjunct agent is limited. AIMS: The effects of saffron as an adjunct to pharmaceutical antidepressants in adults with persistent depression was investigated. METHODS: In this eight-week, randomised, double-blind, placebo-controlled study, adults with persistent depression, currently taking a pharmaceutical antidepressant were given a placebo or a saffron extract (affron®, 14 mg b.i.d.). Primary outcome measures included the clinician-rated Montgomery-Åsberg Depression Rating Scale (MADRS) and self-rated MADRS (MADRS-S). Secondary outcome measures included the Antidepressant Side-Effect Checklist (ASEC) and Short Form-36 Health Survey (SF-36). RESULTS: Of the 160 participants enrolled, 139 provided usable data. Based on the MADRS, depressive symptoms decreased more in participants taking saffron compared with a placebo, with reductions of 41 and 21%, respectively (p = 0.001). However, scores on the MADRS-S decreased 27 and 26% in the saffron and placebo conditions, respectively (p = 0.831). Saffron was associated with a greater reduction in adverse effects of antidepressants (p = 0.019), although this was non-significant after covarying for baseline values (p = 0.449). Quality of life improved in both groups with no significant between-group differences (p = 0.638). CONCLUSION: Adjunctive administration of a standardised saffron extract (affron®) for eight weeks was associated with a greater improvement in depressive symptoms as measured by the clinician-rated MADRS but not the self-report MADRS-S. Given the conflicting results, further research is needed to clarify the clinical benefits of saffron as an adjunctive treatment for adults with persistent depressive symptoms despite antidepressant drug treatment.

Is the association of hypertension and panic disorder explained by clustering of autonomic panic symptoms in hypertensive patients?

BACKGROUND: Autonomic nervous system dysfunction may be implicated in the association of hypertension with panic attacks and panic disorder. We hypothesised that panic symptoms of autonomic origin are more common in attacks experienced by hypertensive than normotensive patients, that autonomic panic symptoms cluster together as a distinct factor, and that this factor is more prevalent in hypertensive patients with panic than in normotensives. METHODS: We analysed all 346 structured questionnaires completed by primary care and hospital clinic patients who had reported experiencing full (n=287) or limited symptom panic attacks (n=59) (268 with hypertension, and 78 never having had hypertension). Frequency of sweating, flushes, and racing heart, symptoms selected prospectively as being most likely of autonomic origin, were compared between hypertensive and normotensive patients. Principal component analysis was performed with varimax orthogonal rotation. Using logistic regression, odds ratios were calculated for association of factor scores with hypertension. RESULTS: Sweating and flushes were significantly more common among hypertensive patients than normotensives (sweating; 65% v 46%, p=0.003, flushes; 55% v 40%, p=0.019). There was no significant difference between groups for frequency of racing heart nor any of the remaining panic symptoms analysed as secondary endpoints. Principal component analysis yielded four factors with eigenvalues >1.0. Factor 1 was dominated by autonomic symptoms, notably sweating and flushes, which had loadings of 0.68 and 0.61. On regression only this autonomic factor showed a significant association with hypertension, the odds ratio being 1.37 (95% C.I. 1.05 to 1.77, p=0.018). CONCLUSIONS: These findings support the possibility that autonomic dysfunction contributes to the association of hypertension with panic.

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.

Development and validation of the Generalized Anxiety Disorder Inventory (GADI).

The psychometric tools used for the assessment of generalized anxiety disorder (GAD) either do not conform to the current concept of the condition or have important limitations. We aimed to develop and validate a new questionnaire for the assessment of symptom profile and severity of GAD. An original pool of potential scale items was subjected to a series of studies in non-clinical and clinical populations, in order to determine the final composition of the scale. The psychometric properties of the new scale, the Generalized Anxiety Disorder Inventory (GADI), were evaluated using a factor analytic model suitable for ordinal data and the Graded Response Model. The precision of measurement of the GADI was quantified through the item information functions.A total of 197 outpatients and 522 non-clinical subjects participated in four studies and completed the GADI. The final 18-item scale was derived from an original pool of 30 potential items. The GADI showed good reliability, convergent and divergent validity. The scale comprises three factors, relating to cognitive, somatic and sleep symptoms. It accurately distinguished GAD patients from non-patient controls. The cognitive factor also distinguished GAD from other anxiety disorders and depression. The GADI is a useful tool in the assessment of the breadth of symptoms and the severity of generalized anxiety disorder in clinical settings.

Effects of tryptophan depletion on selective serotonin reuptake inhibitor-remitted patients with obsessive compulsive disorder.

BACKGROUND: Serotonergic antidepressants are first-line medication therapies for obsessive-compulsive disorder, however it is not known if synaptic serotonin availability is important for selective serotonin reuptake inhibitor efficacy. The present study tested the hypothesis that temporary reduction in central serotonin transmission, through acute tryptophan depletion, would result in an increase in anxiety in selective serotonin reuptake inhibitor-remitted obsessive-compulsive disorder patients. METHODS: Eight patients (four males) with obsessive-compulsive disorder who showed sustained clinical improvement with selective serotonin reuptake inhibitor treatment underwent acute tryptophan depletion in a randomized, double-blind, placebo-controlled, within-subjects design, over two days one week apart. Five hours after consumption of the depleting/sham drink the participants performed a personalized obsessive-compulsive disorder symptom exposure task. Psychological responses were measured using the Spielberger State Anxiety Inventory, Yale-Brown Obsessive Compulsive Scale and Visual Analogue Scales. RESULTS: Free plasma tryptophan to large neutral amino acid ratio decreased by 93% on the depletion day and decreased by 1% on the sham day, as anticipated. Psychological rating scores as measured by Visual Analogue Scale showed a significant decrease in perceived control and increase in interfering thoughts at the time of provocation on the depletion day but not on the sham day. A measure of convergent validity, namely Visual Analogue Scale Similar to past, was significantly higher at the time of provocation on both the depletion and sham days. Both the depletion and time of provocation scores for Visual Analogue Scale Anxiety, Spielberger State Anxiety Inventory, Yale-Brown Obsessive Compulsive Scale and blood pressure were not significant. CONCLUSIONS: Acute tryptophan depletion caused a significant decrease in perceived control and increase in interfering thoughts at the time of provocation. Acute tryptophan depletion had no effect on the Spielberger State Anxiety Inventory or Visual Analogue Scale Anxiety measures, which suggests that the mechanism of action of selective serotonin reuptake inhibitors may be different to that seen in panic, social anxiety and post-traumatic stress disorder. Successful selective serotonin reuptake inhibitor treatment of obsessive-compulsive disorder may involve the ability of serotonin to switch habitual responding to goal-directed behaviour.

Serotonin regulation of the human stress response.

Acute tryptophan depletion (ATD) is a technique that has been used to evaluate the effects on humans of acutely reducing serotonin neurotransmission. We have developed a model using a single breath of 35% CO(2) that activates the hormonal axis and produces autonomic and behavioural arousal, thus modelling a stress response. This study combines ATD and single breath 35% CO(2) inhalation to study stress responses in volunteers. A randomised, double-blinded, placebo-controlled, cross-over trial involving 14 healthy adult volunteers aged between 18 and 65 years was undertaken. Subjects underwent double-blind tryptophan depletion over 2 days and were then crossed over 1 week later. During each study day, at the time of peak depletion, participants were single blinded to receive a single breath of 35% CO(2) or air. This was followed 40 min later by the other gas. Psychological outcomes were assessed with the Spielberger State Anxiety Inventory (SSAI), Visual Analogue Scales (VAS), Panic Inventory (PI), Panic and Agoraphobia Scale (PSI) and Beck Depression Inventory (BDI). Physiological outcome was measured by serial plasma cortisol, prolactin and tryptophan levels, pulse and blood pressure. Tryptophan depletion did not exacerbate 35% CO(2) inhalation effects on anxiety symptoms. Single breath CO(2) robustly increased plasma cortisol levels in comparison to an air inhalation; this was less certain for prolactin levels. ATD influenced the HPA axis (associated with higher cortisol levels), apparently independent of CO(2) or air inhalation stressors. ATD and 35% CO(2) inhalation both induced a pressor response and bradycardia in these normal volunteers. Thirty-five percent CO(2) inhalation and ATD independently activate the human stress response, but do not appear to produce synergistic effects when combined, at least for the conditions produced in this study.

Evidence for serotonin function as a neurochemical difference between fear and anxiety disorders in humans?

The relationships between serotonin and fear and anxiety disorders have been much studied yet many important questions remain, despite selective serotonin reuptake inhibitors having been the primary treatments for these disorders for some time. In order to explore this issue we performed a pooled analysis of six of our studies in remitted patients with a fear/anxiety disorder who were exposed to syndrome-specific aversive stimulation under acute tryptophan depletion. We based our analysis on the hypothesis that the inconsistencies observed in the studies could be predicted by Deakin and Graeff's theory about the dual role of serotonin in responses to threats, whereby serotonin is critical to prevent fear (panic) but not anxiety. In accordance with this view, our results give support to a dissociation of the disorders traditionally grouped under fear and anxiety-related disorders in terms of different roles of serotonin in modulation of responses to aversive stimulation. Implications for future studies and psychiatric nosology are discussed.

Tryptophan depletion reverses the therapeutic effect of selective serotonin reuptake inhibitors in social anxiety disorder.

BACKGROUND: Tryptophan depletion studies have suggested that central serotonin (5-hydroxytryptamine, 5-HT) function mediates the therapeutic effect of selective serotonin reuptake inhibitors (SSRIs) in depression and panic disorder. The present study tested the hypothesis that temporary reduction in central 5-HT transmission, through acute tryptophan depletion, could reverse the therapeutic effect of the SSRIs in social anxiety disorder (SAD) patients. METHODS: Fourteen patients with SAD who showed sustained clinical improvement with SSRI treatment underwent tryptophan depletion in a double-blind, placebo-controlled, crossover design, over 2 days 1 week apart. At the peak time of depletion, the participants also underwent three behavioral challenges: autobiographical script, verbal task, and neutral script. Psychological outcome was assessed with the Spielberger State Anxiety Inventory (STAI) Form Y-1 and visual analog scales (VAS) measuring anxiety, depression, and somatic symptoms. RESULTS: Anxiety was significantly increased on the depletion day compared with the control day, both on the STAI Form Y-1 and composite VAS score. Furthermore, there was a significant depletion x time interaction, explained mainly by the anxiogenic effect of the autobiographical script. In contrast, the verbal and the neutral tasks failed to differentiate between depletion and placebo. CONCLUSIONS: Tryptophan depletion induced significant increase of anxiety in treated SAD patients, which was more prominent during the recital of an autobiographical script. This finding supports the notion that SSRIs improve social anxiety by increasing 5-HT availability. The autobiographical script seems to be a more robust challenge test for SAD than the stressful verbal task.

Inhalation of 35% CO(2) results in activation of the HPA axis in healthy volunteers.

BACKGROUND: The hypothalamo-pituitary-adrenal (HPA) axis is a major stress responsive system in humans. Although there are numerous ways of testing responsiveness of the HPA in experimental animals, this is much more difficult in man. Hypercapnea is a very stressful stimulus for humans and has been used as an anxiogenic probe in psychiatric patients. We have now investigated whether the simple challenge of a single 35% inhalation of CO(2) activates the neuroendocrine system as evidenced by changes in HPA activity, as well as cardiovascular and subjective responses, in healthy volunteers. METHODS: Fourteen healthy male volunteers were recruited. They underwent single vital capacity inhalation of room air and 35% CO(2), in a single blind fashion. Neuroendocrine, cardiovascular and subjective fear measures were taken at regular intervals. RESULTS: CO(2) inhalation produced significant activation of the HPA axis in all subjects, as measured with plasma cortisol. Heart rate was decreased and systolic blood pressure was significantly increased shortly after the inhalation of CO(2). The subjects reported short-lived symptoms of fear with the experimental gas. CONCLUSIONS: Single vital capacity inhalation of 35% CO(2) activated the HPA axis in healthy volunteers. It also had a significant cardiovascular and psychological (anxiogenic) effect, as expected from previous published studies. The test is potentially useful in studying the responsivity of the HPA axis in health and disease.