Table 1 Number of participants, response and quitting rates in seven experimental groups

	Self help	All counselled	Planned number of sessions (total duration of sessions)
	Self help	All counselled	5 (50 minutes)	7 (Booster) (80 minutes)	3 (105 minutes)	5 (Booster) (135 minutes)	5 (210 minutes)	7 (Booster) (240 minutes)
Enrolled participants	1564	4758	1289	263	819	812	749	826
Followed 6 months	743	2411	653	120	431	434	409	433
Response rate	0.48	0.52	0.51	0.46	0.53	0.53	0.55	0.52
Respondent quit rate	0.160**	0.208**	0.198*	0.308*	0.162	0.203	0.232	0.224
95% CI	0.134 to 0.187	0.192 to 0.224	0.167 to 0.228	0.226 to 0.391	0.128 to 0.197	0.165 to 0.241	0.191 to 0.273	0.185 to 0.263
Enrolled quit rate	0.076**	0.108**	0.100*	0.141*	0.085	0.108	0.127	0.117
95% CI	0.063 to 0.089	0.100 to 0.117	0.084 to 0.116	0.099 to 0.183	0.066 to 0.105	0.087 to 0.130	0.103 to 0.151	0.095 to 0.139
Mean number of sessions completed	–	–	1.56	1.83	0.74	0.92	1.38	1.51

**0.005 significance level for the difference between these two rates (χ² test).
*0.05 significance level for the difference between these two rates (χ² test).
No other planned comparisons found significant differences between rates.