Table 3 Meta-regression analysis of study level covariates of lifetime prevalence of any substance, khat, alcohol, and cigarettes smoking among students in Ethiopia

 Year of publication

0.0060609

− 11.68013

0.0124317

0.638

 Study year

13.89607

− 0.0082915

9.605409

0.182

 Sample size

− 0.0003494

0.7741379

0.0002403

0.180

 Female proportion

0.0037158

0.4131199

0.0045819

0.438

 Mean age

− 0.0387067

1.317451

0.0389781

0.347

 Study year

− 0.0020241

4.325688

0.0052509

0.704

 Year of publication

− 0.0021067

4.495044

0.0051577

0.687

 Sample size

0.0000108

0.2432449

0.0000275

0.698

 Female proportion

− 0.100255

0.2853794

0.11553259

0.526

 Mean age

0.0084523

0.0811581

0.0094737

0.383

 Year of publication

0.0042828

− 8.160433

0.0242541

0.863

 Study year

0.0255544

− 50.95082

0.022354

0.275

 Sample size

0.0000688

0.5277942

0.0000622

0.319

 Female proportion

− 0.0035171

0.5924492

0.0042616

0.425

 Mean age

− 0.005842

0.3477194

0.0223419

0.798

 Year of publication

0.0018767

− 3.622797

0.0055397

0.741

 Study year

0.0035468

− 6.980033

0.0053445

0.521

 Sample size

0.0000605

0.097251

0.0430878

0.171

 Female proportion

0.0014625

0.1013142

0.0017218

0.414

 Mean age

− 0.0173243*

0.4966166

0.0075743

0.043