| Participación del sistema opioide endógeno en la adicción a la nicotina | 82 |
| 11 / 2012 | 12 / 2012 | 01 / 2013 | 02 / 2013 | 03 / 2013 | 04 / 2013 | 05 / 2013 | |
| Participación del sistema opioide endógeno en la adicción a la nicotina | 10 | 20 | 12 | 7 | 11 | 12 | 10 |
| 1 | Spain | 38 |
| 2 | Mexico | 18 |
| 3 | United States of America | 6 |
| 4 | Argentina | 5 |
| 5 | Colombia | 3 |
| 6 | Peru | 3 |
| 7 | Venezuela | 3 |
| 8 | Ukraine | 2 |
| 9 | Brazil | 1 |
| 10 | Chile | 1 |
| 1 | Madrid | 10 |
| 2 | Mexico | 10 |
| 3 | Salamanca | 4 |
| 4 | Valencia | 4 |
| 5 | Maracay | 3 |
| 6 | Tarragona | 3 |
| 7 | Alhama | 2 |
| 8 | Barcelona | 2 |
| 9 | Lanús | 2 |
| 10 | Lugo | 2 |