Table 1.
Means and standard deviations of the participant background variables for the Internet addiction and non-Internet addiction groups.
| IA |
Non-IA |
Group differences IA (total) versus non-IA (total) | |||||
|---|---|---|---|---|---|---|---|
| Total (n = 20) | Stress (n = 10) | Placebo (n = 10) | Total (n = 56) | Stress (n = 28) | Placebo (n = 28) | ||
| Age (years), M(SD) | 21.2 (4.4) | 19.7 (1.3) | 22.6 (5.9) | 22.9 (4.8) | 23.1 (5.2) | 22.6 (4.6) | t (36.3) = 1.44, p = 0.16 |
| Sex (males/females) | 5/15 | 3/7 | 2/8 | 20/36 | 10/18 | 10/18 | p = 0.42 |
| BMI (kg/m2), M(SD) | 21.3 (3.5) | 21.4 (2.9) | 21.3 (4.2) | 22.1 (2.8) | 22.0 (2.4) | 22.1 (3.2) | t (24.6) = 0.85, p = 0.41 |
| Days after menstruation, M(SD) | 21.3 (12.0) | 23.8 (13.2) | 18.8 (11.3) | 18.2 (11.8) | 17.9 (13.4) | 18.6 (10.3) | t (19.2) = 0.77, p = 0.45 |
| Drinking frequency (days/week) | U (1) = 531.0, p = 0.62 | ||||||
| >4 | 0 | 0 | 0 | 0 | 0 | 0 | |
| 3–4 | 0 | 0 | 0 | 2 | 1 | 1 | |
| 1–2 | 3 | 2 | 1 | 9 | 6 | 3 | |
| <1 | 17 | 8 | 9 | 45 | 21 | 24 | |
| Drinking quantity per drinking day (units/day) | U (1) = 558.0, p = 0.98 | ||||||
| >6 | 1 | 0 | 1 | 3 | 2 | 1 | |
| 5–6 | 1 | 1 | 0 | 8 | 3 | 5 | |
| 3–4 | 7 | 3 | 4 | 12 | 4 | 8 | |
| <3 | 11 | 6 | 5 | 33 | 19 | 14 | |
| Smoking frequency (days/week) | U (1) = 570.0, p = 0.53 | ||||||
| >4 | 0 | 0 | 0 | 1 | 1 | 0 | |
| 3–4 | 0 | 0 | 0 | 0 | 0 | 0 | |
| 1–2 | 0 | 0 | 0 | 0 | 0 | 0 | |
| <1 | 20 | 10 | 10 | 55 | 27 | 28 | |
| Cigaretts per day, M(SD) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.1 (0.5) | 0.1 (0.8) | 0.0 (0.0) | t (55.0) = 1.00, p = 0.32 |
| IAT score, M(SD) | 61.5 (10.2) | 64.4 (12.7) | 58.5 (6.1) | 35.2 (7.1) | 33.7 (6.6) | 36.6 (7.4) | t (26.0) = 10.67, p < 0.01 |
| CES-D score, M(SD) | 20.7 (10.3) | 16.5 (8.8) | 24.9 (10.5) | 11.9 (7.4) | 13.0 (8.6) | 10.9 (5.9) | t (26.2) = 3.49, p < 0.01 |
| STAI-T score, M(SD) | 54.6 (11.1) | 53.3 (10.7) | 55.8 (11.9) | 43.3 (9.9) | 44.2 (10.4) | 42.5 (9.5) | t (30.5) = 4.00, p < 0.01 |
| PSS score, M(SD) | 31.4 (9.5) | 27.9 (8.7) | 34.8 (9.5) | 22.3 (8.3) | 23.0 (7.9) | 21.6 (8.8) | t (30.0) = 3.75, p < 0.01 |
IA: Internet addiction, IAT: the Japanese version of the internet addiction test, CES-D: the Japanese version of the Center for Epidemiologic Studies—Depression Scale, STAI-T: the Japanese version of the Spielberger State Trait Anxiety Inventory—Trait Form, PSS: the Japanese version of the Perceived Stress Scale.