1. Acute Low Dose Tryptophan Depletion in Volunteers at High Risk for Eating Disorders A Pringle¹, M Browning², M Cooper³ & C Harmer² 1Department of Experimental Psychology, University of Oxford 2Department of Psychiatry, University of Oxford 3Isis Education Centre, University of Oxford
BACKGROUND
5-HT is thought to be important in pathophysiology of eating disorders (EDs, Kaye 2008)
EDs are also associated with biases in the processing of emotionally valenced stimuli (Lee & Shafran 2003)
It is not known if these two findings are connected: Could biases in emotional processing represent a psychological outcome of 5-HT abnormality in EDs?
We used low dose ATD in the ED vulnerable group of female dieters to address this question
RESULTS
ATD decreased subjective ratings of sadness and reduced the urge to restrict on the VAS (ps = 0.04; figure 1), though these effects were small in magnitude
ATD increased selective processing of all the emotional word types in the emotional Stroop (figure 2)
In the SSPT the T- group was slower to respond both “me” and “not me” to ED relevant personality and characteristic words (p=0.01), however, this pattern was evident across all wordtypes suggest a non-specific slowing (figure 3)
ATD did not affect performance on the FERT
Figure 1: Changes in VAS ratings
Sad
Urge to restrict
METHOD
26 healthy female dieters randomised to receive low dose amino acid mixture either missing tryptophan (T-) or balanced (T+) (14 T-, 12 T+)
Modified HAM-D and VAS (subjective mood and cogs about eating, weight & shape) pre and 5 hours post mixture ingestion
Emotional Processing task battery 5 hours post ingestion:
Emotional Stroop: ED relevant eating, weight and shape words & depression relevant social threat words
Self Schema Processing Task (SSPT): Categorise 4 groups of personality and characteristic words as “me” or “not me” (generic positive, generic negative, ED relevant negative, Depression relevant negative)
Facial Expression Recognition Task (FERT, Harmer et al )
Figure 2: Emotional Stroop Effects
Main effect of ATD
CAKE HEAVY FLABBY ALONE
CHEERFUL BOSSY UNASSERTIVE EVIL
CONCLUSION
ATD increased selective processing of negatively valenced stimuli including words relating to eating, weight and shape on the emotional Stroop
ATD may also have some effects on subjective ratings of mood (sadness) and cognitions about eating (urge to restrict) in the absence of clinically relevant changes in objective mood
This approach has the potential to link cognitive and biological theories of EDs with implications for our understanding of the aetiology and treatment of these illnesses
Figure 3: SSPT Reaction times
Abbie Pringle is supported by an MRC studentship