Cognitive Training for Nicotine Dependence

Daily smoking, from the Target Quit Date to End of Treatment (EOT), was assessed by a validated timeline follow-back measure. Based on guidelines for smoking cessation trials, the primary outcome was 7-day point prevalence abstinence at EOT, and abstinence was defined as no self-reported smoking (even a puff) for at least 7 days, with in-person verification by carbon monoxide breath levels (CO \<8ppm). Following standard convention, participants who withdrew or were lost to follow-up were considered smokers.

Time frame: End of treatment (Week 12)

Change in performance on the Continuous Performance Task (attention) between Baseline and End of Treatment (Week 12). In this task, participants are presented with a series of letters at 2.5s intervals and are instructed to respond by pressing the space bar if the same letter appears twice in a row. The outcome is the change in the number of commission errors (the number of times the participant responded to a non-target at EOT minus baseline). There are a total of 125 trials, with 20 target trials (response required) and 85 non-target trials (no response required); therefore the possible range for the change score is -85 to 85. Negative numbers indicate a decrease in commission errors (better performance at EOT compared to baseline); positive numbers indicate an increase in commission errors (worse performance at EOT compared to baseline); and 0 indicates no change.

Time frame: Baseline and Week 12 (EOT)

Population: Participants with performance \>3SD from the mean at Baseline were excluded as outliers.

Change in performance on the Go/No-Go Task (response inhibition) between Baseline and End of Treatment (Week 12). In this task, participants are presented with a series of stimuli (the word PRESS in either green or red). Participants are instructed to respond by pressing the spacebar when the stimulus is green, and to withhold a response when the stimulus is red. The outcome is the change in number of commission errors (failure to withhold a response to a red stimulus) from EOT minus baseline. The potential range for the change score is -42 to 42. Negative numbers indicate a decrease in the number of commission errors (improved performance) from baseline to EOT; positive numbers indicate an increase in commission errors (worse performance); 0 indicates no change.

Time frame: Baseline and Week 12 (EOT)

Population: Participants with performance \>3SD from the mean at baseline were excluded as outliers.

Change in performance on the Digit Span Forward task (working memory) between Baseline and End of Treatment (Week 12). In this task, participants are presented with a series of digits on the computer screen at one second intervals. Participants are then required to enter the digits in order. The number of digits in each series ranges from 3 to 7, and the maximum recall span is the length of the largest series entered correctly. The outcome measure is the change score (calculated by subtracting the Baseline score from the end of treatment score). Change scores can range from -4 to 4. Negative numbers indicate worse performance at EOT; positive numbers indicate better performance at EOT; and 0 indicates no change.

Time frame: Baseline and Week 12 (EOT)

Population: Participants with performance \>3SD from the mean at baseline were excluded as outliers.

Daily smoking from the Target Quit Date to 6 month follow-up was assessed by a validated timeline follow-back measure. Based on guidelines for smoking cessation trials, the secondary outcome was 7-day point prevalence abstinence at the 6 month follow-up, and abstinence was defined as no self-reported smoking (even a puff) for at least 7 days, with in-person verification by carbon monoxide breath levels (CO \<8ppm). Following standard convention, participants who withdrew or were lost to follow-up were considered smokers.

Time frame: 6 month follow-up