Characteristics of RCTs
| Characteristics | N (%) of trials |
| Country of origin | |
| USA | 158 (56.6) |
| UK | 20 (7.2) |
| Multinational | 22 (7.9) |
| Other | 79 (28.3) |
| Year of publication | |
| 1971–1983 | 10 (3.6) |
| 1984–1995 | 61 (21.8) |
| 1996–2007 | 111 (39.8) |
| 2008–2019 | 97 (34.8) |
| Trial size (participants) | |
| >500 | 197 (70.6) |
| <500 | 82 (29.4) |
| Class of pharmacotherapy intervention | |
| Antidepressants | 91 (32.6) |
| nAChR partial agonists | 38 (13.6) |
| NRTs | 121 (43.4) |
| Others | 29 (10.4) |
| Trial funding source | |
| Pharmaceutical industry | 156 (55.9) |
| Non-industry | 87 (31.2) |
| Unspecified | 36 (12.9) |
| Additional behavioural support | |
| Yes | 229 (82.1) |
| No | 24 (8.6) |
| Unknown | 26 (9.3) |
| Participant recruitment | |
| Community volunteers | 155 (55.6) |
| Healthcare setting | 78 (28.0) |
| Smoking cessation clinic | 25 (9.00) |
| Unspecified | 21 (7.40) |
nAChR, nicotinic acetylcholine receptor; NRTs, nicotine replacement therapies; RCTs, randomised controlled trials.