Low-dose tryptophan depletion in recovered depressed women induces impairments in autobiographical memory specificity

• Published in: Psychopharmacologia Vol. 207; no. 3; pp. 499 - 508
• Main Authors: Haddad, Anneke D. M., Williams, J. Mark G., McTavish, Sarah F. B., Harmer, Catherine J.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-12-2009; Springer; Springer Nature B.V
• Subjects: Adult; Adult and adolescent clinical studies; Affect - physiology; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Cognition - physiology; Depression; Depressive Disorder - psychology; Dose-Response Relationship, Drug; Female; Humans; Medical sciences; Memory; Mental depression; Mental Recall - drug effects; Middle Aged; Mood disorders; Neurosciences; Original Investigation; Pattern Recognition, Visual - drug effects; Pharmacology/Toxicology; Psychiatry; Psychology. Psychoanalysis. Psychiatry; Psychomotor Performance - drug effects; Psychopathology. Psychiatry; Psychopharmacology; Tryptophan - blood; Tryptophan - deficiency; Women; Acute tryptophan depletion; Serotonin; Autobiographical memory specificity; Recovered depressed; Mood disorder; Human; Acute; Low dose; Autobiographical memory; Tryptophan; Depression; Depletion; Aminoacid; Neurotransmitter; Female; Woman
• ISSN: 0033-3158; 1432-2072
• DOI: 10.1007/s00213-009-1693-2

Background
Depressed patients perform poorly on tests of autobiographical memory specificity (AMS); this may have negative consequences for other important cognitive abilities, delays recovery from mood episodes, and, in recovered patients, may mediate vulnerability to future episodes. Although the cognitive mechanisms underlying AMS deficits are beginning to be understood, the neurobiological mechanisms remain unclear. Serotonin is implicated in both depression and long-term memory; therefore, temporary lowering of brain serotonin function via acute tryptophan depletion (ATD) offers a means of studying the role of serotonin in autobiographical memory specificity.
Materials and methods
In this study, 24 previously depressed women underwent low-dose ATD or sham depletion and completed tests of initial and delayed memory, recollection- and familiarity-based recognition, and AMS.
Results
ATD did not differentially affect state mood. Compared with sham depletion, ATD impaired immediate recall on the Auditory Verbal Learning Test. Although ATD did not differentially impair recollection- and familiarity-based recognition, it did slow recognition of positive words. ATD also reduced autobiographical memory specificity in response to negative cue words.
Discussion
The results confirm previous findings that low-dose ATD can reinstate depression-congruent biases in cognition without causing depressive mood in vulnerable populations. The ATD-induced reduction in memory specificity suggests that serotonergic dysfunction may mediate depressive deficits in autobiographical memory; the interaction of cognitive and neurobiological vulnerability mechanisms is discussed.