The anxiolytic and cognitive effects of L-theanine

Although there have been a number of studies investigating the anxiolytic
effects, there have rarely been significant effects of L-theanine in isolation
beyond increases in calmness and relaxation on self-report measures. However,
none of the studies so far has looked at physiological anxiety responses
directly. The Fear-Potentiated Startle (FPS) with threat of shock is a robust
way of inducing and measuring a fear state in almost every individual, allowing
a direct test of anxiolytic effects (Klumpers et al., 2010; METC protocol
#07-165). We will test the hypothesis that L-theanine administration will
provide anxiolytic effects based on reduced FPS and subjective anxiety during
the FPS test and other anxiety test battery scores when compared to a placebo
condition.

A secondary hypothesis is that participants with a higher score on trait
anxiety will show greater improvements when compared to participants with a
lower score. People with a higher level of trait anxiety have more room to
improve and there are indications from previous research that this group
receives stronger beneficial effects of L-theanine (Higashiyama, Htay, Ozeki,
Juneja, & Kapoor, 2011; Kobayashi et al., 1998; Unno et al., 2013). An
interesting result is the study by Higashiyama et al. (2011), where
participants were divided into two groups based on their trait anxiety, as
measured by the Manifest Anxiety Scale scores. Results showed that only
participants with high levels of anxiety received beneficial cognitive effects
of the L-theanine administration based on reaction time and accuracy of a
mental arithmetic task. Given that high levels of anxiety are often detrimental
to cognitive performance, the increased performance is thought to be due to
reduced anxiety.

Primary Objective: The primary objective is to show that L-theanine has
beneficial anxiolytic in healthy individuals. With the current experiment setup
that entails the following effects of L-theanine compared to placebo:
• Reduced startle effect on Fear-Potentiated Startle
• Reduced levels of anxiety after FPS, Trier social stress test and Stroop, as
measured by the STAI state and Bond & Lader Visual Analogue Scale
• Increased levels of calmness as measured by the STAI state and Bond & Lader
Visual Analogue Scale
• Increased alpha band activity during EEG resting state
• Decreased blood pressure, heart rate and alpha amylase levels after FPS,
Trier mental arithmetic test and Stroop


Secondary Objective(s): The secondary objective is to show that for
participants with high levels of trait anxiety, L-theanine can also provide
beneficial cognitive effects due to decreased anxiety. With the current
experiment setup that entails the following effects of L-theanine compared to
placebo for the high anxiety group:
• Increased attentional and reaction time performance on Higashiyama
replication task.
• Increased interference performance on the Stroop
• Increased performance on the Trier mental arithmetic test

This study follows a within subjects, double blind, placebo controlled
crossover design.

Subjects will be administered 200 mg of nutritional supplement L-theanine 30
minutes before start of the test battery. This dosage is in line with previous
research. The product will be obtained from the Dutch company AOV, which
specializes in vitamin and nutritional supplements. Their supplier, Taiyo, is
the only producer of Suntheanine, a synthetically produced form of L-Theanine.
AOV capsules are made from tullulan and contain 200 mg Suntheanin. The
additional material in the capsule is the additive substance
hydroxypropylmethylcellulose (HPMC), used in a variety of food and medicinal
products. The placebo will be an identical looking capsule, also supplied by
AOV.

The burden and risk involved in participating in this study is negligible in
our opinion. Previous research has not found any side effects of L-theanine and
it is regarded safe as a food additive and supplement in the United States.
Additionally, the intensity of the electric shocks is determined on an
individual level, and is well tolerated. Participation is voluntary, and
participants can withdraw from the study at any time, this will be clearly
explained to participants.

The decrease of the number of secondary outcome parameters in study 2 reduces
the burden for the subjects considerably.