The catecholamine neurotransmitter precursor tyrosine increases anger during exposure to severe psychological stress.
Level 2 - randomized trial
Individual randomized controlled trial.
PubMed 25220844 · doi:10.1007/s00213-014-3727-7
What was done
A double-blind, between-subjects randomized controlled trial assessed whether tyrosine supplementation alters responses to severe psychological stress during Survival, Evasion, Resistance, and Escape (SERE) training. Seventy-eight healthy military personnel received either tyrosine (300 mg/kg total, given in food bars as two 150 mg/kg doses 60 minutes before mock interrogations; N = 36) or placebo (N = 36). Profile of Mood States (POMS), salivary cortisol, and heart rate were measured at baseline (preceding academic week) and immediately after mock interrogations.
What was found
Severe stress significantly elevated heart rate, cortisol, and all POMS mood dimensions (tension, depression, anger, fatigue, vigor, confusion; all p < .001). Tyrosine significantly increased anger during stress relative to placebo (treatment-by-session interaction, p = .002). Tyrosine produced no significant changes in other mood subscales, cortisol, or heart rate.
Why it matters
Tyrosine is commonly explored for stress resilience, but in this severe psychological stress model, its primary effect was an isolated increase in subjective anger without modifying cardiovascular or endocrine stress responses.
Limits
The study tested a healthy, highly trained military cohort in an extreme simulated captivity environment, limiting generalizability to civilian populations or milder chronic stressors. Absolute baseline and post-stress values, effect sizes, and exact group dropouts (78 enrolled vs. 72 analyzed) are not provided in the abstract.
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