Some baseline variables apparently influence adherence to therapy. In one study, mean daily cigarette consumption, expired carbon monoxide, plasma nicotine and cotinine, and Fagerstrom Tolerance Questionnaire (FTQ) scores (44) were significantly higher in the dropout group than in the adherent group (1). Alterman et al. (25) concluded that greater dependence on tobacco was associated with less patch use, indicating that patients who smoked more cigarettes were less adherent to treatment with patches.

Depression is an important psychological factor associated with cessation of smoking. A higher prevalence of depressive symptoms would theoretically increase the risk of nonadherence to treatment (45). Differing results of studies of this association have been reported. Some studies showed that smokers with a history of major depression who were not depressed at the time of a 4-week treatment programme had a lower abstinence rate than did smokers without a history of depression. In another study, smokers with a history of major depression in an 8-week multicomponent cognitive behavioural group plus nicotine-gum programme, had a significantly higher abstinence rate than smokers with a history of depression who were treated with nicotine plus a standard programme of information (3,45). Ginsberg et al. suggested that cognitive - behavioural sessions emphasizing group cohesion and social support among smokers with a history of depression maintains adherence in this population (45). A satisfactory explanation of this link will require further research (3,24,31).

Other variables, such as gender, racial or ethnic background, history of psychiatric pathology (25), weight gain (29,30), craving and withdrawal symptoms are reported as being potential predictors of patch adherence. However, because there are no validated measures of these variables, the available data are insufficient to assess their effects on adherence.

During an NRT programme, investigators observed some factors that had a positive effect on adherence. These included motivation (25), attendance at cessation classes, access to free NRT, higher education levels, older age, advice from physicians (26), and more frequent contact with physicians and pharmacists

(35). These factors were also reported as predictive of success in stopping smoking. The analysis of the studies showed that these factors have proven to be statistically significant in increasing abstinence rates, but there is no measure proving their association with adherence.