| Methods |
Design: five group parallel trial
Purpose: examine the effect of 'covert sensitization' on smoking behaviour |
| Participants |
Patients: smokers
Baseline comparability: yes (number of smoked cigarettes) |
| Interventions |
Placebo: sessions of listening to illusory subliminal messages
Untreated:
‐no sessions with continuous monitoring of smoking rates
‐no sessions with pre‐post monitoring of smoking rates
Experimental:
‐covert sensitization sessions (visualization of feelings of nausea and vomiting as imagining themselves smoking)
‐self control suggestion sessions (told to quit by their own effort)
(Co‐intervention: NS) |
| Outcomes |
Mean number of cigarettes smoked per day |
| Notes |
Standard deviation of untreated and placebo means estimated from t‐test of baseline‐post intervention change in the placebo group |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Adequate sequence generation? |
Unclear risk |
NS |
| Allocation concealment? |
Unclear risk |
NS |
| Blinding?
Treatment provider |
High risk |
Not described as double‐blind (placebo/covert sensitization) |
| Blinding?
Outcome assessor |
Unclear risk |
NS |
| Incomplete outcome data addressed?
All outcomes |
High risk |
Drop‐out > 15% or NS |
| Free of selective reporting? |
High risk |
No protocol available. Standard deviation of untreated and placebo means estimated from t‐test of baseline‐post intervention change in the placebo group |
| Free of other bias? |
Low risk |
|
| No signs of variance inequality or skewness? |
High risk |
Either variance inequality (F‐test statistically significant) or skewness (1.64 standard deviations exceeds the mean) |
| Trial size > 49? |
High risk |
N = 20 |
| Clearly concealed allocation + trial size > 49 + drop‐out max 15% |
High risk |
Trial size < 49 |
