Table 3. Open in new tab The effects of...

Task

SMD (LCI, UCI; P-value)

I² [%] (LCI, UCI)

SMD re-expressed (CI)

SRT, first hour: Kahathuduwa et al. (2017)³⁶; Dassanayake et al. (2022)³⁸; Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²

100 mg theanine dose from Dassanayake et al. (2022)³⁸

−0.04 (−0.78, 0.70; 0.87)

87.09 (59.29, 99.09)

−1.29 ms (−23.44, 20.86)

200 mg theanine dose from Dassanayake et al. (2022)³⁸

−0.09 (−0.95, 0.77; 0.77)

90.12 (68.59, 99.31)

−2.64 ms (−28.30, 23.03)

400 mg theanine dose from Dassanayake et al. (2022)³⁸

0.06 (−0.47, 0.60; 0.73)

76.15 (26.95, 98.23)

1.92 ms (−13.97, 17.81)

SRT, second hour: Baba et al. (2021)⁴⁰; Haskell et al. (2008)⁴¹

−0.11 (−1.22, 1.00; 0.42)

0.00 (0.00, 99.78)

−5.13 ms (−55.43, 45.18)

CR time, first hour: Kahathuduwa et al. (2017)³⁶; Dassanayake et al. (2022)³⁸; Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²

100 mg theanine dose from Dassanayake et al. (2022)³⁸

−0.35 (−0.61,−0.10; 0.02)

0.00 (0.00, 88.21)

−18.17 ms (−31.44,−4.91)

200 mg theanine dose from Dassanayake et al. (2022)³⁸

−0.32 (−0.64, 0.01; 0.05)

0.29 (0.00, 92.09)

−16.28 ms (−32.87, 0.31)

400 mg theanine dose from Dassanayake et al. (2022)³⁸

−0.35 (−0.62,−0.08; 0.03)

0.00 (0.00, 89.01)

−17.83 ms (−31.63,−4.03)

CR time, second hour: Kahathuduwa et al., (2018)²¹; Haskell et al., (2008)⁴¹

−0.69 (−4.82, 3.44; 0.28)

49.55 (0.00, 99.88)

−36.9 ms (−257.78, 183.97)

CR accuracy, first hour: Kahathuduwa et al. (2017)³⁶; Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²

−0.10 (−1.14, 0.93; 0.71)

72.36 (0, 99.29)

−0.33 % (−3.66, 3.01)

RVIP reaction time, second hour: Dassanayake et al. (2022)³⁸; Haskell et al. (2008)⁴¹

100 mg theanine dose from Dassanayake et al. (2022)³⁸

−0.01 (−1.78, 1.76; 0.96)

26.02 (0.00, 99.91)

−0.46 ms (−103.91, 102.99)

200 mg theanine dose from Dassanayake et al. (2022)³⁸

−0.21 (−0.78, 0.36; 0.13)

0.00 (0.00, 99.30)

−12.17 ms (−45.04, 20.70)

400 mg theanine dose from Dassanayake et al. (2022)³⁸

−0.17 (−0.30,−0.04; 0.04)

0.00 (0.00, 85.76)

−9.74 ms (−16.92,−2.56)

RVIP accuracy, second hour: Dassanayake et al. (2022)³⁸; Haskell et al. (2008)⁴¹

100 mg theanine dose from Dassanayake et al. (2022)³⁸

0.07 (−0.94, 1.07; 0.55)

0.00 (0.00, 99.87)

0.48% (−6.61, 7.57)

200 mg theanine dose from Dassanayake et al. (2022)³⁸

0.18 (−0.01, 0.37; 0.05)

0.00 (0.00, 96.29)

1.27% (−0.08, 2.62)

400 mg theanine dose from Dassanayake et al. (2022)³⁸

0.17 (0.10, 0.23; 0.02)

0.00 (0.00, 66.62)

1.21% (0.75, 1.67)

DVT reaction time, second hour: Baba et al. (2021)⁴⁰; Haskell et al. (2008)⁴¹

0.06 (−0.24, 0.36; 0.23)

0.00 (0.00, 95.35)

2.15 ms (−8.09, 12.39)

DVT accuracy, second hour: Baba et al. (2021)⁴⁰; Haskell et al. (2008)⁴¹

−0.05 (−1.68, 1.59; 0.77)

0.00 (0.00, 99.87)

−0.34 % (−12.01, 11.33)

MD (LCI, UCI; P-value)

I² [%] (LCI, UCI)

RVIP reaction time, first hour: Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²

−2.34 (−96.44, 91.76; 0.81)

0.00 (0.00, 19.84)

RVIP accuracy, first hour: Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²

0.92 (−6.49, 8.33; 0.36)

0.00 (0.00, 92.21)

Serial 3 subtractions, first hour: Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²

−0.21 (−9.45, 9.03; 0.82)

0.00 (0.00, 96.91)

Serial 7 subtractions, first hour: Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²

0.18 (−14.57, 14.94; 0.90)

30.47 (0.00, 97.74)

Task

SMD (LCI, UCI; P-value)

I² [%] (LCI, UCI)

SMD re-expressed (CI)

SRT, first hour: Kahathuduwa et al. (2017)³⁶; Dassanayake et al. (2022)³⁸; Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²

100 mg theanine dose from Dassanayake et al. (2022)³⁸

−0.04 (−0.78, 0.70; 0.87)

87.09 (59.29, 99.09)

−1.29 ms (−23.44, 20.86)

200 mg theanine dose from Dassanayake et al. (2022)³⁸

−0.09 (−0.95, 0.77; 0.77)

90.12 (68.59, 99.31)

−2.64 ms (−28.30, 23.03)

400 mg theanine dose from Dassanayake et al. (2022)³⁸

0.06 (−0.47, 0.60; 0.73)

76.15 (26.95, 98.23)

1.92 ms (−13.97, 17.81)

SRT, second hour: Baba et al. (2021)⁴⁰; Haskell et al. (2008)⁴¹

−0.11 (−1.22, 1.00; 0.42)

0.00 (0.00, 99.78)

−5.13 ms (−55.43, 45.18)

CR time, first hour: Kahathuduwa et al. (2017)³⁶; Dassanayake et al. (2022)³⁸; Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²

100 mg theanine dose from Dassanayake et al. (2022)³⁸

−0.35 (−0.61,−0.10; 0.02)

0.00 (0.00, 88.21)

−18.17 ms (−31.44,−4.91)

200 mg theanine dose from Dassanayake et al. (2022)³⁸

−0.32 (−0.64, 0.01; 0.05)

0.29 (0.00, 92.09)

−16.28 ms (−32.87, 0.31)

400 mg theanine dose from Dassanayake et al. (2022)³⁸

−0.35 (−0.62,−0.08; 0.03)

0.00 (0.00, 89.01)

−17.83 ms (−31.63,−4.03)

CR time, second hour: Kahathuduwa et al., (2018)²¹; Haskell et al., (2008)⁴¹

−0.69 (−4.82, 3.44; 0.28)

49.55 (0.00, 99.88)

−36.9 ms (−257.78, 183.97)

CR accuracy, first hour: Kahathuduwa et al. (2017)³⁶; Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²

−0.10 (−1.14, 0.93; 0.71)

72.36 (0, 99.29)

−0.33 % (−3.66, 3.01)

RVIP reaction time, second hour: Dassanayake et al. (2022)³⁸; Haskell et al. (2008)⁴¹

100 mg theanine dose from Dassanayake et al. (2022)³⁸

−0.01 (−1.78, 1.76; 0.96)

26.02 (0.00, 99.91)

−0.46 ms (−103.91, 102.99)

200 mg theanine dose from Dassanayake et al. (2022)³⁸

−0.21 (−0.78, 0.36; 0.13)

0.00 (0.00, 99.30)

−12.17 ms (−45.04, 20.70)

400 mg theanine dose from Dassanayake et al. (2022)³⁸

−0.17 (−0.30,−0.04; 0.04)

0.00 (0.00, 85.76)

−9.74 ms (−16.92,−2.56)

RVIP accuracy, second hour: Dassanayake et al. (2022)³⁸; Haskell et al. (2008)⁴¹

100 mg theanine dose from Dassanayake et al. (2022)³⁸

0.07 (−0.94, 1.07; 0.55)

0.00 (0.00, 99.87)

0.48% (−6.61, 7.57)

200 mg theanine dose from Dassanayake et al. (2022)³⁸

0.18 (−0.01, 0.37; 0.05)

0.00 (0.00, 96.29)

1.27% (−0.08, 2.62)

400 mg theanine dose from Dassanayake et al. (2022)³⁸

0.17 (0.10, 0.23; 0.02)

0.00 (0.00, 66.62)

1.21% (0.75, 1.67)

DVT reaction time, second hour: Baba et al. (2021)⁴⁰; Haskell et al. (2008)⁴¹

0.06 (−0.24, 0.36; 0.23)

0.00 (0.00, 95.35)

2.15 ms (−8.09, 12.39)

DVT accuracy, second hour: Baba et al. (2021)⁴⁰; Haskell et al. (2008)⁴¹

−0.05 (−1.68, 1.59; 0.77)

0.00 (0.00, 99.87)

−0.34 % (−12.01, 11.33)

MD (LCI, UCI; P-value)

I² [%] (LCI, UCI)

RVIP reaction time, first hour: Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²

−2.34 (−96.44, 91.76; 0.81)

0.00 (0.00, 19.84)

RVIP accuracy, first hour: Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²

0.92 (−6.49, 8.33; 0.36)

0.00 (0.00, 92.21)

Serial 3 subtractions, first hour: Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²

−0.21 (−9.45, 9.03; 0.82)

0.00 (0.00, 96.91)

Serial 7 subtractions, first hour: Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²

0.18 (−14.57, 14.94; 0.90)

30.47 (0.00, 97.74)

Table 3.

Open in new tab

The effects of theanine, compared to placebo, on simple reaction time, choice reaction time and accuracy, rapid visual information processing reaction time and accuracy, digit vigilance task reaction time and accuracy, and serial 3 and 7 subtractions.

Task	SMD (LCI, UCI; P-value)	I² [%] (LCI, UCI)	SMD re-expressed (CI)
SRT, first hour: Kahathuduwa et al. (2017)³⁶; Dassanayake et al. (2022)³⁸; Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²
100 mg theanine dose from Dassanayake et al. (2022)³⁸	−0.04 (−0.78, 0.70; 0.87)	87.09 (59.29, 99.09)	−1.29 ms (−23.44, 20.86)
200 mg theanine dose from Dassanayake et al. (2022)³⁸	−0.09 (−0.95, 0.77; 0.77)	90.12 (68.59, 99.31)	−2.64 ms (−28.30, 23.03)
400 mg theanine dose from Dassanayake et al. (2022)³⁸	0.06 (−0.47, 0.60; 0.73)	76.15 (26.95, 98.23)	1.92 ms (−13.97, 17.81)
SRT, second hour: Baba et al. (2021)⁴⁰; Haskell et al. (2008)⁴¹	−0.11 (−1.22, 1.00; 0.42)	0.00 (0.00, 99.78)	−5.13 ms (−55.43, 45.18)
CR time, first hour: Kahathuduwa et al. (2017)³⁶; Dassanayake et al. (2022)³⁸; Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²
100 mg theanine dose from Dassanayake et al. (2022)³⁸	−0.35 (−0.61,−0.10; 0.02)	0.00 (0.00, 88.21)	−18.17 ms (−31.44,−4.91)
200 mg theanine dose from Dassanayake et al. (2022)³⁸	−0.32 (−0.64, 0.01; 0.05)	0.29 (0.00, 92.09)	−16.28 ms (−32.87, 0.31)
400 mg theanine dose from Dassanayake et al. (2022)³⁸	−0.35 (−0.62,−0.08; 0.03)	0.00 (0.00, 89.01)	−17.83 ms (−31.63,−4.03)
CR time, second hour: Kahathuduwa et al., (2018)²¹; Haskell et al., (2008)⁴¹	−0.69 (−4.82, 3.44; 0.28)	49.55 (0.00, 99.88)	−36.9 ms (−257.78, 183.97)
CR accuracy, first hour: Kahathuduwa et al. (2017)³⁶; Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²	−0.10 (−1.14, 0.93; 0.71)	72.36 (0, 99.29)	−0.33 % (−3.66, 3.01)
RVIP reaction time, second hour: Dassanayake et al. (2022)³⁸; Haskell et al. (2008)⁴¹
100 mg theanine dose from Dassanayake et al. (2022)³⁸	−0.01 (−1.78, 1.76; 0.96)	26.02 (0.00, 99.91)	−0.46 ms (−103.91, 102.99)
200 mg theanine dose from Dassanayake et al. (2022)³⁸	−0.21 (−0.78, 0.36; 0.13)	0.00 (0.00, 99.30)	−12.17 ms (−45.04, 20.70)
400 mg theanine dose from Dassanayake et al. (2022)³⁸	−0.17 (−0.30,−0.04; 0.04)	0.00 (0.00, 85.76)	−9.74 ms (−16.92,−2.56)
RVIP accuracy, second hour: Dassanayake et al. (2022)³⁸; Haskell et al. (2008)⁴¹
100 mg theanine dose from Dassanayake et al. (2022)³⁸	0.07 (−0.94, 1.07; 0.55)	0.00 (0.00, 99.87)	0.48% (−6.61, 7.57)
200 mg theanine dose from Dassanayake et al. (2022)³⁸	0.18 (−0.01, 0.37; 0.05)	0.00 (0.00, 96.29)	1.27% (−0.08, 2.62)
400 mg theanine dose from Dassanayake et al. (2022)³⁸	0.17 (0.10, 0.23; 0.02)	0.00 (0.00, 66.62)	1.21% (0.75, 1.67)
DVT reaction time, second hour: Baba et al. (2021)⁴⁰; Haskell et al. (2008)⁴¹	0.06 (−0.24, 0.36; 0.23)	0.00 (0.00, 95.35)	2.15 ms (−8.09, 12.39)
DVT accuracy, second hour: Baba et al. (2021)⁴⁰; Haskell et al. (2008)⁴¹	−0.05 (−1.68, 1.59; 0.77)	0.00 (0.00, 99.87)	−0.34 % (−12.01, 11.33)
	MD (LCI, UCI; P-value)	I² [%] (LCI, UCI)
RVIP reaction time, first hour: Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²	−2.34 (−96.44, 91.76; 0.81)	0.00 (0.00, 19.84)
RVIP accuracy, first hour: Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²	0.92 (−6.49, 8.33; 0.36)	0.00 (0.00, 92.21)
Serial 3 subtractions, first hour: Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²	−0.21 (−9.45, 9.03; 0.82)	0.00 (0.00, 96.91)
Serial 7 subtractions, first hour: Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²	0.18 (−14.57, 14.94; 0.90)	30.47 (0.00, 97.74)

Task	SMD (LCI, UCI; P-value)	I² [%] (LCI, UCI)	SMD re-expressed (CI)
SRT, first hour: Kahathuduwa et al. (2017)³⁶; Dassanayake et al. (2022)³⁸; Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²
100 mg theanine dose from Dassanayake et al. (2022)³⁸	−0.04 (−0.78, 0.70; 0.87)	87.09 (59.29, 99.09)	−1.29 ms (−23.44, 20.86)
200 mg theanine dose from Dassanayake et al. (2022)³⁸	−0.09 (−0.95, 0.77; 0.77)	90.12 (68.59, 99.31)	−2.64 ms (−28.30, 23.03)
400 mg theanine dose from Dassanayake et al. (2022)³⁸	0.06 (−0.47, 0.60; 0.73)	76.15 (26.95, 98.23)	1.92 ms (−13.97, 17.81)
SRT, second hour: Baba et al. (2021)⁴⁰; Haskell et al. (2008)⁴¹	−0.11 (−1.22, 1.00; 0.42)	0.00 (0.00, 99.78)	−5.13 ms (−55.43, 45.18)
CR time, first hour: Kahathuduwa et al. (2017)³⁶; Dassanayake et al. (2022)³⁸; Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²
100 mg theanine dose from Dassanayake et al. (2022)³⁸	−0.35 (−0.61,−0.10; 0.02)	0.00 (0.00, 88.21)	−18.17 ms (−31.44,−4.91)
200 mg theanine dose from Dassanayake et al. (2022)³⁸	−0.32 (−0.64, 0.01; 0.05)	0.29 (0.00, 92.09)	−16.28 ms (−32.87, 0.31)
400 mg theanine dose from Dassanayake et al. (2022)³⁸	−0.35 (−0.62,−0.08; 0.03)	0.00 (0.00, 89.01)	−17.83 ms (−31.63,−4.03)
CR time, second hour: Kahathuduwa et al., (2018)²¹; Haskell et al., (2008)⁴¹	−0.69 (−4.82, 3.44; 0.28)	49.55 (0.00, 99.88)	−36.9 ms (−257.78, 183.97)
CR accuracy, first hour: Kahathuduwa et al. (2017)³⁶; Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²	−0.10 (−1.14, 0.93; 0.71)	72.36 (0, 99.29)	−0.33 % (−3.66, 3.01)
RVIP reaction time, second hour: Dassanayake et al. (2022)³⁸; Haskell et al. (2008)⁴¹
100 mg theanine dose from Dassanayake et al. (2022)³⁸	−0.01 (−1.78, 1.76; 0.96)	26.02 (0.00, 99.91)	−0.46 ms (−103.91, 102.99)
200 mg theanine dose from Dassanayake et al. (2022)³⁸	−0.21 (−0.78, 0.36; 0.13)	0.00 (0.00, 99.30)	−12.17 ms (−45.04, 20.70)
400 mg theanine dose from Dassanayake et al. (2022)³⁸	−0.17 (−0.30,−0.04; 0.04)	0.00 (0.00, 85.76)	−9.74 ms (−16.92,−2.56)
RVIP accuracy, second hour: Dassanayake et al. (2022)³⁸; Haskell et al. (2008)⁴¹
100 mg theanine dose from Dassanayake et al. (2022)³⁸	0.07 (−0.94, 1.07; 0.55)	0.00 (0.00, 99.87)	0.48% (−6.61, 7.57)
200 mg theanine dose from Dassanayake et al. (2022)³⁸	0.18 (−0.01, 0.37; 0.05)	0.00 (0.00, 96.29)	1.27% (−0.08, 2.62)
400 mg theanine dose from Dassanayake et al. (2022)³⁸	0.17 (0.10, 0.23; 0.02)	0.00 (0.00, 66.62)	1.21% (0.75, 1.67)
DVT reaction time, second hour: Baba et al. (2021)⁴⁰; Haskell et al. (2008)⁴¹	0.06 (−0.24, 0.36; 0.23)	0.00 (0.00, 95.35)	2.15 ms (−8.09, 12.39)
DVT accuracy, second hour: Baba et al. (2021)⁴⁰; Haskell et al. (2008)⁴¹	−0.05 (−1.68, 1.59; 0.77)	0.00 (0.00, 99.87)	−0.34 % (−12.01, 11.33)
	MD (LCI, UCI; P-value)	I² [%] (LCI, UCI)
RVIP reaction time, first hour: Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²	−2.34 (−96.44, 91.76; 0.81)	0.00 (0.00, 19.84)
RVIP accuracy, first hour: Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²	0.92 (−6.49, 8.33; 0.36)	0.00 (0.00, 92.21)
Serial 3 subtractions, first hour: Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²	−0.21 (−9.45, 9.03; 0.82)	0.00 (0.00, 96.91)
Serial 7 subtractions, first hour: Haskell et al. (2008)⁴¹; Dodd et al. (2015)⁴²	0.18 (−14.57, 14.94; 0.90)	30.47 (0.00, 97.74)

Abbreviations: CR, choice reaction; DVT, digit vigilance task; I², proportion of variation in the observed effects attributable to variation in the true effect; LCI, lower CI; MD, mean difference; RVIP, rapid visual information processing; SMD, standardized mean difference; SRT, simple reaction time; UCI, upper CI.

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