Attention Deficit Hyperactivity Disorder (ADHD) is a common neurodevelopmental disorder that affects millions of people worldwide. It is characterized by difficulty in sustaining attention, impulsivity, and hyperactivity. Studies have shown that L-Tyrosine can help reduce symptoms of ADHD, such as hyperactivity, impulsivity, and inattention.

Uses on focus and attention

L-Tyrosine is an amino acid that has been studied for its potential to help with ADHD symptoms. In recent years, a number of double-blind and placebo-controlled studies testing the effects of tyrosine administration on cognition have been published. As one of the first published studies, Colzato et al. (2013) found that the intake of tyrosine had a positive effect on the performance in an n-back working memory task. In another study, Colzato et al. (2014) tested the effect of tyrosine on the performance in a stop-signal task. Colzato et al. (2013, 2014) argue that more challenging cognitive operations exhaust the available cognitive resources mediated by dopamine which can be counteracted by supplementing tyrosine. This suggests that tyrosine can be administered to improve cognitive performance in tasks that are modulated by the prefrontal dopamine system and would thus apply to the executive functions controlled by the PFC. Besides, it may also help improve sleep quality and reduce stress and anxiety, while more research is needed.

How does it work?

L-Tyrosine is the precursor of the neurotransmitter dopamine (DA) and norepinephrine (NE). High densities of dopaminergic neurons are located in the prefrontal cortex (PFC), where DA plays an essential role in mediating executive functions such as working memory, selective top-down attention, behavioral flexibility, and decision-making. DA appears to enhance the efficiency of the prefrontal neural transmission through D1 receptors, which increase the spike rate of pyramidal neurons in selective frequency bands.

However, the relation is not simply linear. While an intermediate level of DA is assumed to result in a higher level of cognitive performance in tasks modulated by the PFC, too low or too high levels of DA are assumed to cause detrimental effects. This relation is referred to as the inverted-U curve hypothesis. In addition to pharmacological modulation of dopaminergic neurotransmission, e.g., with amphetamine, tyrosine has been proposed as a non-pharmacological dietary supplement that might have the potential to "correct" prefrontal DA to the optimal level.

Reference

[1] Frings, C., Domes, G., Friehs, M. A., Gei?ler, C. F., & Schneider, K. (2019). Food for Your Mind? The Effect of Tyrosine on Selective Attention. Journal of Cognitive Enhancement?: Towards the Integration of Theory and Practice, 4 1, 285–295. https://doi.org/10.1007/s41465-019-00146-3