Results : We confirmed the importance of the 4 main factors influencing SC : ( 1 ) environmental factors , ( 2 ) genomic factors , ( 3 ) gene-environment interactions , and ( 4 ) evidence -based interventions .
The model demonstrates the complex network of factors influencing SC .
Background : Smoking behaviour is a major public health problem worldwide .
Several sources have confirmed the implication of genomic factors in smoking behaviour .
These factors interact both with environmental factors and interventions to develop a certain behaviour .
Objectives : Describing the environmental and genomic factors as well as the interventions influencing smoking cessation  ( SC ) and developing a working model incorporating the different factors influencing SC were our main objectives .
Genetic variants in the serotonin transporter influence the efficacy of bupropion and nortriptyline in smoking cessation.
AIMS We investigated whether variants in the serotonin transporter gene ( SLC6A4 ) influence  smoking cessation rates  using antidepressant therapy ( i.e. bupropion and nortriptyline ) . DESIGN Pharmacogenetic ( secondary ) analysis of a r and omized , placebo-controlled efficacy trial of bupropion and nortriptyline for smoking cessation . SETTING Single-centre study , Maastricht University , the Netherl and s. PARTICIPANTS A total of 214 of 255 ( 84 % ) current daily smokers participating in a r and omized controlled efficacy trial . MEASUREMENTS Subjects were genotyped for three functional variants in SLC6A4 ( 5-HTTLPR , STin2 , rs25531 ) . Primary outcome measures were prolonged abstinence from weeks 4 - 12 , 4 - 26 and 4 - 52 . Secondary outcome measures included 7-day point prevalence abstinence at weeks 4 , 12 , 26 and 52 . FINDINGS Carriers of the 5-HTTLPR high-activity L-variant had higher prolonged cessation rates with bupropion than placebo [ odds ratio ( OR ) = 1.44 , 95 % confidence interval ( CI ) = 1.01 - 2.05 , P = 0.04 ] . Combining the three variants result ed in increased prolonged cessation rates for both bupropion and nortriptyline among carriers of four to five high-activity variants ( bupropion : OR = 2.00 , 95 % CI = 1.21 - 3.29 , P = 0.01 ; nortriptyline : OR = 1.91 , 95 % CI = 1.02 - 3.56 , P = 0.04 ) . Similar results were found for point prevalence abstinence . CONCLUSIONS Bupropion and nortriptyline seem to be more effective in smoking cessation among SLC6A4 high-activity variant carriers , probably by blocking the increased serotonin transporter activity , thereby increasing serotonin levels . Prospect i ve studies have to assess if this can improve cessation rates when treatment is targeted at individuals based on their genotypes
Results : We confirmed the importance of the 4 main factors influencing SC : ( 1 ) environmental factors , ( 2 ) genomic factors , ( 3 ) gene-environment interactions , and ( 4 ) evidence -based interventions .
The model demonstrates the complex network of factors influencing SC .
Background : Smoking behaviour is a major public health problem worldwide .
Several sources have confirmed the implication of genomic factors in smoking behaviour .
These factors interact both with environmental factors and interventions to develop a certain behaviour .
Objectives : Describing the environmental and genomic factors as well as the interventions influencing smoking cessation  ( SC ) and developing a working model incorporating the different factors influencing SC were our main objectives .