Table 4.
Multivariate negative binomial regression model on the willingness to use a CE-drug (n = 2,887)
| |
IRR
a
|
95% CI
b
|
|---|---|---|
| Drug characteristics | ||
| Magnitude of enhancement effect (Ref. 5 percent): |
|
|
|
▪ a factor of two |
1.010 |
[0.849,1.201] |
|
▪ a factor of three |
1.329** |
[1.120,1.577] |
| Probability of enhancement effect (Ref. 5 percent): |
|
|
|
▪ 50 percent |
1.287** |
[1.081,1.533] |
|
▪ 100 percent |
1.392*** |
[1.177,1.646] |
| Severity of side effects (Ref. very light depression): |
|
|
|
▪ moderate depression |
0.924 |
[0.781,1.093] |
|
▪ very strong depression |
0.881 |
[0.746,1.041] |
| Probability of side effects (Ref. one of 1,000,000 users): |
|
|
|
▪ one of 1,000 users |
0.955 |
[0.815,1.119] |
|
▪ every user |
0.634*** |
[0.533,0.754] |
| Drug price (Ref. free): |
|
|
|
▪ 20 Euros |
1.118 |
[0.955,1.310] |
|
▪ 100 Euros |
0.683*** |
[0.572,0.815] |
|
Social environment
|
|
|
| Peer prevalence (Ref. none): |
|
|
|
▪ every second |
1.287*** |
[1.089,1.522] |
|
▪ every one |
1.321** |
[1.113,1.568] |
| Social suggestions (Ref. never): |
|
|
|
▪ sometimes |
0.887 |
[0.749,1.051] |
|
▪ very often |
1.071 |
[0.907,1.265] |
| Social disapproval (Ref. no criticism): |
|
|
|
▪ moderate criticism |
0.926 |
[0.788,1.090] |
|
▪ very strong criticism |
0.713*** |
[0.600,0.846] |
|
Personal characteristics
|
|
|
| Risk attitudes |
1.012 |
[0.980,1.045] |
| Academic procrastination |
1.112** |
[1.034,1.196] |
| Study motivation |
0.897** |
[0.839,0.960] |
| Cognitive test anxiety (CTA) |
1.383*** |
[1.245,1.535] |
| Competencies |
1.048 |
[0.915,1.199] |
| Internalized social norms |
0.673*** |
[0.644,0.702] |
| Prior CE-drug use |
2.409*** |
[1.873,3.097] |
|
Demographic variables
|
|
|
| Male (Ref. female) |
0.949 |
[0.812,1.110] |
| Agec |
0.969 |
[0.928,1.012] |
| Field of study (Ref. sports): |
|
|
|
▪ Linguistics & cultural studies |
1.260 |
[0.792,2.004] |
|
▪ Legal, economic, & social sciences |
1.237 |
[0.763,2.006] |
|
▪ Mathematics & natural sciences |
1.261 |
[0.797,1.995] |
|
▪ Human medicine & health |
1.272 |
[0.710,2.279] |
|
▪ Agriculture, forestry, & nutritional sciences |
1.285 |
[0.716,2.307] |
|
▪ Engineering |
1.845* |
[1.089,3.126] |
|
▪ Arts & science of art |
1.669 |
[0.981,2.839] |
| Log-pseudolikelihood (full model) |
-3566.2 |
|
| Log-pseudolikelihood (base model) | -3848.1 | |
*p < 0.05, **p < .01, ***p < .001 (Wald tests, robust standard errors).
a Adjusted Incidence Rate Ratios (IRR).
b Confidence Intervals (CI).
c Age was treated as a metric variable (see Table 2 for the 14 measured categories).