[1] Birdsall TC. 5-Hydroxytryptophan: a clinically-effective serotonin precursor. Alternative Medicine review 1998; 3: 271–280.
[2] Berger M, Gray JA, Roth BL. The expanded biology of serotonin. Annu Rev Med 2009; 60: 355–366.
[3] Reiter RJ, Tan D, Terron MP, et al. Melatonin and its metabolites: new findings regarding their production and their radical scavenging actions. Acta Biochim Pol 2007; 54: 1–9.
[4] Bottiglieri T, Laundy M, Crellin R, et al. Homocysteine, folate, methylation, and monoamine metabolism in depression. J Neurol Neurosurg Psychiatr 2000; 69: 228–232.
[5] Herr N, Bode C, Duerschmied D. The Effects of Serotonin in Immune Cells. Front Cardiovasc Med 2017; 4: 48.
[6] Nau F, Miller J, Saravia J, et al. Serotonin 5-HT2 receptor activation prevents allergic asthma in a mouse model. Am J Physiol Lung Cell Mol Physiol 2015; 308: L191-198.
[7] Hernandez ME, Martinez-Fong D, Perez-Tapia M, et al. Evaluation of the effect of selective serotonin-reuptake inhibitors on lymphocyte subsets in patients with a major depressive disorder. European Neuropsychopharmacology 2010; 20: 88–95.
[8] Nazimek K, Strobel S, Bryniarski P, et al. The role of macrophages in anti-inflammatory activity of antidepressant drugs. Immunobiology 2017; 222: 823–830.
[9] Stone RA, Worsdell YM, Fuller RW, et al. Effects of 5-hydroxytryptamine and 5-hydroxytryptophan infusion on the human cough reflex. Journal of Applied Physiology 1993; 74: 396–401.
[10] Juhl JH. Fibromyalgia and the serotonin pathway. Altern Med Rev 1998; 3: 367–375.
[11] Nutrition Facts for Lean Chicken Breast (Cooked). myfooddata, https://tools.myfooddata.com/nutrition-facts/171140/wt9 (accessed 1 December 2020).
[12] Singer HS, Mink JW, Gilbert DL, et al. Inherited Metabolic Disorders Associated with Extrapyramidal Symptoms. In: Movement Disorders in Childhood. Elsevier, pp. 164–204.
[13] Majewski M, Kozlowska A, Thoene M, et al. Overview of the role of vitamins and minerals on the kynurenine pathway in health and disease. J Physiol Pharmacol 2016; 67: 3–19.
[14] Yabut JM, Crane JD, Green AE, et al. Emerging Roles for Serotonin in Regulating Metabolism: New Implications for an Ancient Molecule. Endocrine Reviews 2019; 40: 1092–1107.
[15] Patrick RP, Ames BN. Vitamin D and the omega-3 fatty acids control serotonin synthesis and action, part 2: relevance for ADHD, bipolar disorder, schizophrenia, and impulsive behavior. The FASEB Journal 2015; 29: 2207–2222.
[16] Teff KL, Young SN, Blundell JE. The effect of protein or carbohydrate breakfasts on subsequent plasma amino acid levels, satiety and nutrient selection in normal males. Pharmacol Biochem Behav 1989; 34: 829–837.
[17] Kardinaal AFM, van Erk MJ, Dutman AE, et al. Quantifying phenotypic flexibility as the response to a high-fat challenge test in different states of metabolic health. FASEB J 2015; 29: 4600–4613.
[18] Kennedy SJ, Ryan L, Clegg ME. The Effects of a Functional Food Breakfast on Gluco-Regulation, Cognitive Performance, Mood, and Satiety in Adults. Nutrients 2020; 12: 2974.
[19] Gendall KA, Joyce PR. Meal-induced changes in tryptophan:LNAA ratio: effects on craving and binge eating. Eat Behav 2000; 1: 53–62.
[20] Turner EH, Loftis JM, Blackwell AD. Serotonin a la carte: supplementation with the serotonin precursor 5-hydroxytryptophan. Pharmacol Ther 2006; 109: 325–338.
[21] Birdsall TC. 5-Hydroxytryptophan: a clinically-effective serotonin precursor. Altern Med Rev 1998; 3: 271–280.
[22] Meyers S. Use of neurotransmitter precursors for treatment of depression. Altern Med Rev 2000; 5: 64–71.
[23] Golden RN, Gaynes BN, Ekstrom RD, et al. The efficacy of light therapy in the treatment of mood disorders: a review and meta-analysis of the evidence. Am J Psychiatry 2005; 162: 656–662.
[24] Lambert GW, Reid C, Kaye DM, et al. Effect of sunlight and season on serotonin turnover in the brain. Lancet 2002; 360: 1840–1842.
[25] Khan S, Duan P, Yao L, et al. Shiftwork-Mediated Disruptions of Circadian Rhythms and Sleep Homeostasis Cause Serious Health Problems. International Journal of Genomics 2018; 2018: 1–11.
[26] Oyane NMF, Bjelland I, Pallesen S, et al. Seasonality is associated with anxiety and depression: the Hordaland health study. J Affect Disord 2008; 105: 147–155.
[27] Winthorst WH, Roest AM, Bos EH, et al. Self-Attributed Seasonality of Mood and Behavior: A Report from the Netherlands Study of Depression and Anxiety. Depression and Anxiety 2014; 31: 517–523.
[28] Grimaldi S, Partonen T, Haukka J, et al. Seasonal vegetative and affective symptoms in the Finnish general population: Testing the dual vulnerability and latitude effect hypotheses. Nordic Journal of Psychiatry 2009; 63: 397–404.
[29] Sansone RA, Sansone LA. Sunshine, serotonin, and skin: a partial explanation for seasonal patterns in psychopathology? Innov Clin Neurosci 2013; 10: 20–24.
[30] Slominski A, Wortsman J, Tobin DJ. The cutaneous serotoninergic/melatoninergic system: securing a place under the sun. FASEB J 2005; 19: 176–194.
[31] Gambichler T, Bader A, Vojvodic M, et al. Impact of UVA exposure on psychological parameters and circulating serotonin and melatonin. BMC Dermatol 2002; 2: 6.
[32] Savitz J, Drevets WC, Smith CM, et al. Putative neuroprotective and neurotoxic kynurenine pathway metabolites are associated with hippocampal and amygdalar volumes in subjects with major depressive disorder. Neuropsychopharmacology 2015; 40: 463–471.
[33] Oxenkrug G. Insulin resistance and dysregulation of tryptophan-kynurenine and kynurenine-nicotinamide adenine dinucleotide metabolic pathways. Mol Neurobiol 2013; 48: 294–301.
[34] Wichers MC, Koek GH, Robaeys G, et al. IDO and interferon-alpha-induced depressive symptoms: a shift in hypothesis from tryptophan depletion to neurotoxicity. Mol Psychiatry 2005; 10: 538–544.
[35] Papp M, Litwa E, Gruca P, et al. Anxiolytic-like activity of agomelatine and melatonin in three animal models of anxiety. Behav Pharmacol 2006; 17: 9–18.
[36] Posadzki PP, Bajpai R, Kyaw BM, et al. Melatonin and health: an umbrella review of health outcomes and biological mechanisms of action. BMC Med 2018; 16: 18.
[37] Miller CL. The Kynurenine pathway: Modeling the interaction between genes and nutrition in Schizophrenia. Journal of Orthomolecular Medicine 2011; 26: 59–84.
[38] Bouayed J, Rammal H, Soulimani R. Oxidative stress and anxiety: relationship and cellular pathways. Oxid Med Cell Longev 2009; 2: 63–67.
[39] Kelly CB, McDonnell AP, Johnston TG, et al. The MTHFR C677T polymorphism is associated with depressive episodes in patients from Northern Ireland. J Psychopharmacol 2004; 18: 567–571.
[40] Wan L, Li Y, Zhang Z, et al. Methylenetetrahydrofolate reductase and psychiatric diseases. Translational Psychiatry 2018; 8: 1–12.
[41] Young SN. How to increase serotonin in the human brain without drugs. J Psychiatry Neurosci 2007; 32: 394–399.
[42] Gezondheidsenquête/Leefstijlmonitor 2019. CBS, https://www.cbs.nl/nl-nl/nieuws/2020/17/helft-nederlanders-voldeed-in-2019-aan-beweegrichtlijnen (23 April 2020).
[43] Hidaka BH. Depression as a disease of modernity: explanations for increasing prevalence. J Affect Disord 2012; 140: 205–214.
[44] Mudyanadzo TA, Hauzaree C, Yerokhina O, et al. Irritable Bowel Syndrome and Depression: A Shared Pathogenesis. Cureus; 10. DOI: 10.7759/cureus.3178.
[45] Cocchi M, Traina G. Tryptophan and Membrane Mobility as Conditioners and Brokers of Gut–Brain Axis in Depression. Applied Sciences 2020; 10: 4933.
[46] Whitney MS, Shemery AM, Yaw AM, et al. Adult Brain Serotonin Deficiency Causes Hyperactivity, Circadian Disruption, and Elimination of Siestas. J Neurosci 2016; 36: 9828–9842.
[47] Hardeland R. Neurobiology, pathophysiology, and treatment of melatonin deficiency and dysfunction. ScientificWorldJournal 2012; 2012: 640389.
[48] Jangid P, Malik P, Singh P, et al. Comparative study of efficacy of l-5-hydroxytryptophan and fluoxetine in patients presenting with first depressive episode. Asian J Psychiatr 2013; 6: 29–34.
[49] Meloni M, Puligheddu M, Carta M, et al. Efficacy and safety of 5-hydroxytryptophan on depression and apathy in Parkinson’s disease: a preliminary finding. European Journal of Neurology 2020; 27: 779–786.
[50] Kaneko I, Sabir MS, Dussik CM, et al. 1,25-Dihydroxyvitamin D regulates expression of the tryptophan hydroxylase 2 and leptin genes: implication for behavioral influences of vitamin D. FASEB J 2015; 29: 4023–4035.
[51] Sabir MS, Haussler MR, Mallick S, et al. Optimal vitamin D spurs serotonin: 1,25-dihydroxyvitamin D represses serotonin reuptake transport (SERT) and degradation (MAO-A) gene expression in cultured rat serotonergic neuronal cell lines. Genes Nutr 2018; 13: 19.
[52] Zhang X, Beaulieu J-M, Sotnikova TD, et al. Tryptophan Hydroxylase-2 Controls Brain Serotonin Synthesis. Science 2004; 305: 217–217.
[53] Verhelst G. Griffonia simplicifolia (Vahl ex DC.) Baill. (Slaapmutsjeskruid). In: Groot handboek geneeskrachtige planten - 9e druk. Wevelgem, Belgium: Mannavita BVBA, 2019.
[54] Schruers K, van Diest R, Overbeek T, et al. Acute L-5-hydroxytryptophan administration inhibits carbon dioxide-induced panic in panic disorder patients. Psychiatry Res 2002; 113: 237–243.
[55] Maron E, Tõru I, Vasar V, et al. The Effect of 5-Hydroxytryptophan on Cholecystokinin-4-Induced Panic Attacks in Healthy Volunteers. J Psychopharmacol 2004; 18: 194–199.
[56] Maffei ME. 5-Hydroxytryptophan (5-HTP): Natural Occurrence, Analysis, Biosynthesis, Biotechnology, Physiology and Toxicology. Int J Mol Sci; 22. Epub ahead of print 26 December 2020. DOI: 10.3390/ijms22010181.
[57] Bruni O, Ferri R, Miano S, et al. l-5-Hydroxytryptophan treatment of sleep terrors in children. Eur J Pediatr 2004; 163: 402–407.
[58] Amer A, Breu J, McDermott J, et al. 5-Hydroxy-L-tryptophan suppresses food intake in food-deprived and stressed rats. Pharmacol Biochem Behav 2004; 77: 137–143.
[59] Rondanelli M, Opizzi A, Faliva M, et al. Relationship between the absorption of 5-hydroxytryptophan from an integrated diet, by means of Griffonia simplicifolia extract, and the effect on satiety in overweight females after oral spray administration. Eat Weight Disord 2012; 17: e22-28.
[60] Nicolodi M, Sicuteri F. Fibromyalgia and Migraine, Two Faces of the Same Mechanism. In: Filippini GA, Costa CVL, Bertazzo A (eds) Recent Advances in Tryptophan Research. Boston, MA: Springer US, pp. 373–379.
[61] Nicolodi M, Sicuteri F. Fibromyalgia and Migraine, Two Faces of the Same Mechanism. In: Filippini GA, Costa CVL, Bertazzo A (eds) Recent Advances in Tryptophan Research. Boston, MA: Springer US, pp. 373–379.
[62] Puttini PS, Caruso I. Primary Fibromyalgia Syndrome and 5-Hydroxy-L-Tryptophan: A 90-Day Open Study. J Int Med Res 1992; 20: 182–189.
[63] Caruso I, Sarzi Puttini P, Cazzola M, et al. Double-blind study of 5-hydroxytryptophan versus placebo in the treatment of primary fibromyalgia syndrome. J Int Med Res 1990; 18: 201–209.
[64] Becker S, Schweinhardt P. Dysfunctional neurotransmitter systems in fibromyalgia, their role in central stress circuitry and pharmacological actions on these systems. Pain Res Treat 2012; 2012: 741746.
[65] Panconesi A. Serotonin and migraine: a reconsideration of the central theory. J Headache Pain 2008; 9: 267–276.
[66] De Giorgis G, Miletto R, Iannuccelli M, et al. Headache in association with sleep disorders in children: a psychodiagnostic evaluation and controlled clinical study--L-5-HTP versus placebo. Drugs Exp Clin Res 1987; 13: 425–433.
[67] Ribeiro CA. L-5-Hydroxytryptophan in the prophylaxis of chronic tension-type headache: a double-blind, randomized, placebo-controlled study. For the Portuguese Head Society. Headache 2000; 40: 451–456.
[68] Esposito M, Precenzano F, Sorrentino M, et al. A Medical Food Formulation of Griffonia simplicifolia/Magnesium for Childhood Periodic Syndrome Therapy: An Open-Label Study on Motion Sickness. J Med Food 2015; 18: 916–920.
[69] Emanuele E, Bertona M, Minoretti P, et al. An open-label trial of L-5-hydroxytryptophan in subjects with romantic stress. Neuro Endocrinol Lett 2010; 31: 663–666.
[70] Trouillas P, Brudon F, Adeleine P. Improvement of cerebellar ataxia with levorotatory form of 5-hydroxytryptophan. A double-blind study with quantified data processing. Arch Neurol 1988; 45: 1217–1222.
[71] Mendlewicz J, Youdim MB. Antidepressant potentiation of 5-hydroxytryptophan by L-deprenil in affective illness. J Affect Disord 1980; 2: 137–146.
[72] Turner EH, Blackwell AD. 5-Hydroxytryptophan plus SSRIs for interferon-induced depression: Synergistic mechanisms for normalizing synaptic serotonin. Medical Hypotheses 2005; 65: 138–144.
[73] Cangiano C, Laviano A, Ben MD, et al. Effects of oral 5-hydroxy-tryptophan on energy intake and macronutrient selection in non-insulin dependent diabetic patients. Int J Obes 1998; 22: 648–654.
[74] Shaw K, Turner J, Del Mar C. Tryptophan and 5-hydroxytryptophan for depression. Cochrane Database Syst Rev 2002; CD003198.
[75] Titus F, Dávalos A, Alom J, et al. 5-Hydroxytryptophan versus methysergide in the prophylaxis of migraine. Randomized clinical trial. Eur Neurol 1986; 25: 327–329.
[76] Shell W, Bullias D, Charuvastra E, et al. A randomized, placebo-controlled trial of an amino acid preparation on timing and quality of sleep. Am J Ther 2010; 17: 133–139.
[77] Das YT, Bagchi M, Bagchi D, et al. Safety of 5-hydroxy-l-tryptophan. Toxicology Letters 2004; 150: 111–122.
[78] Hinz M, Stein A, Uncini T. 5-HTP efficacy and contraindications. Neuropsychiatr Dis Treat 2012; 8: 323–328.
[79] Jacobsen JPR, Krystal AD, Krishnan KRR, et al. Adjunctive 5-Hydroxytryptophan Slow-Release for Treatment-Resistant Depression: Clinical and Preclinical Rationale. Trends Pharmacol Sci 2016; 37: 933–944.
[80] Buckley NA, Dawson AH, Isbister GK. Serotonin syndrome. BMJ 2014; 348: g1626–g1626.
[81] Aliño JJ, Gutierrez JL, Iglesias ML. 5-Hydroxytryptophan (5-HTP) and a MAOI (nialamide) in the treatment of depressions. A double-blind controlled study. Int Pharmacopsychiatry 1976; 11: 8–15.
[82] van Hiele LJ. L-5-Hydroxytryptophan in Depression: the First Substitution Therapy in Psychiatry? Neuropsychobiology 1980; 6: 230–240.
[83] Kious BM, Sabic H, Sung Y-H, et al. An open-label pilot study of combined augmentation with creatine monohydrate and 5-hydroxytryptophan for SSRI- or SNRI-resistant depression in adult women. J Clin Psychopharmacol 2017; 37: 578–583.
[84] Kulkarni SK, Bhutani MK, Bishnoi M. Antidepressant activity of curcumin: involvement of serotonin and dopamine system. Psychopharmacology (Berl) 2008; 201: 435–442.
[85] Mukai T, Kishi T, Matsuda Y, et al. A meta-analysis of inositol for depression and anxiety disorders: INOSITOL AND DEPRESSION AND ANXIETY DISORDERS. Hum Psychopharmacol Clin Exp 2014; 29: 55–63.
[86] Frosini M, Sesti C, Dragoni S, et al. Interactions of taurine and structurally related analogues with the GABAergic system and taurine binding sites of rabbit brain. Br J Pharmacol 2003; 138: 1163–1171.
[87] Salve J, Pate S, Debnath K, et al. Adaptogenic and Anxiolytic Effects of Ashwagandha Root Extract in Healthy Adults: A Double-blind, Randomized, Placebo-controlled Clinical Study. Cureus. Epub ahead of print 25 December 2019. https://doi.org/10.7759/cureus.6466
[88] Jafarpoor N, Abbasi-Maleki S, Asadi-Samani M, et al. Evaluation of antidepressant-like effect of hydroalcoholic extract of Passiflora incarnata in animal models of depression in male mice. J Herbmed Pharmacol 2014; 3: 41–45.
[89] Shulgin A, Shulgin A. 6-MeO-THßC, pinoline. In: TIHKAL: The Continuation, https://isomerdesign.com/PiHKAL/read.php?domain=tk&id=44 (1997, accessed 5 August 2020).