No antidepressant-like acute effects of bright light on emotional information processing in healthy volunteers.

RATIONALE: Bright light treatment (BLT) is an efficacious antidepressant intervention, but its mechanism of action is not well understood. Antidepressant drugs acutely affect how emotional information is processed, pushing the brain to prioritise positive relative to negative input. Whether BLT could have a similar effect is not known to date. OBJECTIVE: To test whether BLT acutely influences emotional information processing similar to antidepressant drugs, using an established healthy volunteer assay. METHODS: Following a double-blind, parallel-group design, 49 healthy volunteers (18-65 years, 26 females) were randomly allocated to 60-min BLT (≥ 10,000 lux) or sham-placebo treatment early in the morning in autumn/winter. Immediately after treatment, emotional information processing was assessed using the Oxford Emotional Test Battery, a validated set of behavioural tasks tapping into emotional information processing in different cognitive domains. Participants also completed questionnaires before and after treatment to assess changes in subjective state. RESULTS: The BLT group did not show significantly more positively biased emotional information processing compared to the placebo group (p > 0.05 for all measures). After adjustment for pre-treatment scores, there were also no significant post-treatment differences between groups in subjective state (p > 0.05 for all measures). CONCLUSIONS: BLT did not show immediate effects on emotional information processing in an established healthy volunteer assay. Thus, BLT might exert its clinical effects through a different (cognitive) mechanism than other antidepressant interventions. Future studies should corroborate this finding including clinical populations and more intensive treatment regimes, and control for potential chronobiological effects.

Subchronic treatment with St John's wort produces a positive shift in emotional processing in healthy volunteers.

BACKGROUND: The neurocognitive model of antidepressant treatment in depression states that antidepressants work by producing relatively immediate positive shifts in emotional processing, which translate into clinical improvement with time. St John's Wort has shown antidepressant potential in randomised controlled trials; however, its pharmacological actions are broad and it is unknown whether treatment also produces changes in emotional processing. AIMS: We investigated whether short-term treatment with St John's wort has similar effects on emotional processing to those reported with other antidepressants such as selective serotonergic reuptake inhibitors. METHODS: Forty-eight healthy participants were given St John's wort or placebo treatment for seven days. On day 7 they completed a battery of tasks to measure emotional processing and other elements of cognition. RESULTS: St John's wort treatment produced similar changes to other antidepressants, for example reducing recognition of disgusted faces and attention to fearful faces, while increasing memory for positive words. We failed to find evidence for an effect of St John's wort on other aspects of cognition including working memory. CONCLUSIONS: These findings lend support to the theory that the production of early positive biases in emotional processing may be a common feature of all clinically effective antidepressants with diverse pharmacological mechanisms.

Prebiotic intake reduces the waking cortisol response and alters emotional bias in healthy volunteers.

RATIONALE: There is now compelling evidence for a link between enteric microbiota and brain function. The ingestion of probiotics modulates the processing of information that is strongly linked to anxiety and depression, and influences the neuroendocrine stress response. We have recently demonstrated that prebiotics (soluble fibres that augment the growth of indigenous microbiota) have significant neurobiological effects in rats, but their action in humans has not been reported. OBJECTIVES: The present study explored the effects of two prebiotics on the secretion of the stress hormone, cortisol and emotional processing in healthy volunteers. METHODS: Forty-five healthy volunteers received one of two prebiotics (fructooligosaccharides, FOS, or Bimuno®-galactooligosaccharides, B-GOS) or a placebo (maltodextrin) daily for 3 weeks. The salivary cortisol awakening response was sampled before and after prebiotic/placebo administration. On the final day of treatment, participants completed a computerised task battery assessing the processing of emotionally salient information. RESULTS: The salivary cortisol awakening response was significantly lower after B-GOS intake compared with placebo. Participants also showed decreased attentional vigilance to negative versus positive information in a dot-probe task after B-GOS compared to placebo intake. No effects were found after the administration of FOS. CONCLUSION: The suppression of the neuroendocrine stress response and the increase in the processing of positive versus negative attentional vigilance in subjects supplemented with B-GOS are consistent with previous findings of endocrine and anxiolytic effects of microbiota proliferation. Further studies are therefore needed to test the utility of B-GOS supplementation in the treatment of stress-related disorders.

Folic acid supplementation for prevention of mood disorders in young people at familial risk: a randomised, double blind, placebo controlled trial.

BACKGROUND: Clinical mood disorders often become clinically manifest in the later teenage years and early twenties and can be associated with a poor long-term prognosis. The primary prevention of these disorders would therefore have great public health value. Nutritional supplements are a feasible intervention for primary prevention and several epidemiological studies have indicated links between low folate status and depressive symptomatology in the general population. METHOD: A randomised, double blind, parallel group, placebo-controlled trial in which participants, aged 14-24 years, at increased familial risk of mood disorder, were randomised to folic acid (2.5 mg daily) or identical placebo liquid for a maximum of 36 months. Primary outcome data (the onset of a DSM-IV mood disorder) were collected from 112 participants; 56 per group. RESULTS: The incidence of mood disorder in the folic acid and placebo groups were 14.3% and 17.9% respectively, a non-significant difference. However, there was post-hoc evidence that folic acid delayed the time to onset of mood disorder in those participants who became unwell. LIMITATIONS: Small sample size and rate of onset of mood disorders lower than expected. CONCLUSIONS: Although long term folic acid supplementation was well tolerated, with high levels of adherence, there was no evidence that it reduced the incidence of mood disorder compared to those taking placebo.

Acute administration of the cannabinoid CB1 antagonist rimonabant impairs positive affective memory in healthy volunteers.

BACKGROUND: Emotional processing measures are sensitive to acute administration of clinically useful antidepressant drugs. We wished to test the hypothesis that these models would also be able to detect agents likely to cause depression as an adverse effect. The anti-obesity drug and cannabinoid type 1 receptor antagonist, rimonabant, is associated with significant rates of depression and anxiety in clinical use. MATERIALS AND METHODS: Thirty healthy adult volunteers were randomly assigned to receive a single dose of rimonabant (20 mg) or lactose placebo in a double-blind, between-groups design. Three hours after medication administration, subjects undertook an emotional processing test battery including facial emotion recognition, emotional word attentional dot probe, self-relevant word classification, emotional and declarative memory and the emotion-potentiated acoustic startle response. Subjective state was assessed via self-report measures. RESULTS: A single dose of rimonabant did not alter subjective mood. However, rimonabant selectively reduced incidental recall of positive self-relevant adjectives, an effect contrary to that seen following the administration of antidepressants. There were no effects of rimonabant on the other measures of emotional processing. CONCLUSIONS: These results suggest that a single dose of rimonabant decreases positive emotional memory in the absence of changes in subjective state. Further studies are required to examine whether rimonabant might produce a wider range of negative emotional biases with repeated treatment.

The role of serotonin in nonnormative risky choice: the effects of tryptophan supplements on the "reflection effect" in healthy adult volunteers.

Risky decision-making involves weighing good and bad outcomes against their probabilities in order to determine the relative values of candidate actions. Although human decision-making sometimes conforms to rational models of how this weighting is achieved, irrational (or nonnormative) patterns of risky choice, including shifts between risk-averse and risk-seeking choices involving equivalent-value gambles (the "reflection effect"), are frequently observed. In the present experiment, we investigated the role of serotonin in decision-making under conditions of uncertainty. Fifteen healthy adult volunteers received a treatment of 3 g per day of the serotonin precursor, tryptophan, in the form of dietary supplements over a 14-day period, whereas 15 age- and IQ-matched control volunteers received a matched placebo substance. At test, all participants completed a risky decision-making task involving a series of choices between two simultaneously presented gambles, differing in the magnitude of their possible gains, the magnitude of their possible losses, and the probabilities with which these outcomes were delivered. Tryptophan supplements were associated with alterations in the weighting of gains and small losses perhaps reflecting reduced loss-aversion, and a marked and significant diminution of the reflection effect. We conclude that serotonin activity plays a significant role in nonnormative risky decision-making under conditions of uncertainty.

Fos immunocytochemical studies on the neuroanatomical sites of action of acute tyrosine depletion in the rat brain.

RATIONALE: Acute depletion of brain tyrosine using a tyrosine-free amino acid mixture offers a nutritional approach to reduce central catecholamine function. Recent preclinical data suggest that tyrosine-free amino acid mixtures may have region-specific effects through targeting dopamine neurones. OBJECTIVES: Here we used fos immunocytochemistry to examine the neuroanatomical sites of action of a tyrosine-free amino acid mixture administered either alone or combined with amphetamine. METHODS: Rats (male, Sprague Dawley, 240-260 g) were administered (IP) either a tyrosine-free amino acid mixture (1 g/kg), or the same mixture supplemented with tyrosine and phenylalanine (1 g/kg). Mixtures were injected twice (1 h apart) followed 1 h later by amphetamine (2 mg/kg SC). Two hours later, cardiac perfusion was performed and brains were processed for fos immunocytochemistry. Fos positive cells were counted using computer imaging software. RESULTS: The tyrosine-free amino acid mixture alone did not alter fos expression in ten regions of the rat forebrain compared to saline controls. However, the mixture reduced the increase in fos expression evoked by amphetamine. This effect was region-specific and was greatest in caudate putamen, nucleus accumbens, bed nucleus stria terminalis and lateral habenula, and lacking in other areas including cingulate and insular cortices, lateral septum and central amygdaloid nucleus. Moreover, in most regions the effect of the tyrosine-free mixture was less after tyrosine and phenylalanine supplementation. CONCLUSIONS: In summary, a tyrosine-free amino acid mixture reduced amphetamine-induced fos expression but this effect was region-specific and included dopamine-rich regions. These data further support the idea that tyrosine depletion strategies have potential as treatments for mania and other hyperdopaminergic states.