Changes in Prevalence of Depression and Anxiety Following Smoking Cessation: Results From an International Cohort Study (ATTEMPT)

Smoking cessation improves physical health and reduces the risk of premature death (Taylor et al. 2002; Doll et al. 2004). However, its effect on mental health is uncertain (West & Jarvis, 2005). Cross-sectional studies consistently show a clear association between smoking and poor mental health, with current smokers having a higher prevalence of several psychiatric disorders including depression and anxiety than never-and ex-smokers (Glassman et al. 1990; Breslau et al. 1994; Breslau, 1995; Breslau & Klein, 1999; Farrell et al. 2001; Degenhardt et al. 2001; Benjet et al. 2004; Grant et al. 2004; Wiesbeck et al. 2008). This may be due to several reasons. Smoking behaviour and poor mental health may share a common aetiology based on genetic vulnerability (Kendler et al. 1993), early childhood environment (Goodwin et al. 2004) and personality traits (Goodwin & Hamilton, 2002). In addition, smoking may worsen mental health and stopping may improve it, or people with worse mental health could be more likely to start smoking and find it more difficult to stop, e.g. because they self-medicate (Breslau et al. 1998). Indeed, longitudinal studies show both that psychiatric illnesses lead to later smoking uptake (Brown et al. 1996; Patton et al. 1998; Breslau et al. 1998, 2004) and that starting to smoke increases the risk of subsequent psychiatric morbidity (Johnson et al. 2000; Klungsoyr et al. 2006; Steuber & Danner, 2006; Boden et al. 2010; Kang & Lee, 2010), suggesting a reciprocal relationship. However, most research has focused on either the onset of mental illness following uptake of smoking or uptake of smoking following the onset of mental illness. Less is known about the effects of smoking cessation on mental health in general and depression and anxiety in particular.

A large body of opinion postulates that smoking may, through the actions of nicotine, have beneficial effects on mental health, for example, acting as an anxiolytic, and aid in self-medication to relieve perceived psychological or physiological symptoms (Morrell & Cohen, 2006; Morissette et al. 2007; Ziedonis et al. 2008). If that were the case, one might expect mental health to deteriorate, particularly in vulnerable individuals who stop smoking. In agreement with this, some reports indicate increased incidence of depressive episodes in people with a history of major depressive disorder who have stopped smoking, linking these to cessation (Flanagan & Maany, 1982; Glassman et al. 1990, 2001; Aubin, 2009). Moreover, general population studies have shown that mood disturbances do not necessarily resolve following a month of abstinence from smoking (Gilbert et al. 1999, 2002). Furthermore, smokers with a history of depression or those who experience more negative affect during a quit attempt are more likely to relapse (Kassel et al. 2003; Piasecki et al. 2003; Rohde et al. 2004).

However, short- to longer-term cessation has also been associated with a decrease in stress and anxiety and no worsening of depressed mood in the general population (West & Hajek, 1997; Hajek et al. 2010; Bolam et al. 2011) and with a faster recovery among those with a current diagnosis of depression or anxiety (Jamal et al. 2012). While there is evidence that acute negative affect may precipitate relapse (Shiffman & Waters, 2004), meta-analyses have failed to corroborate findings that a history of depression predicts smoking cessation outcomes (Hitsman et al. 2003; Covey et al. 2006). In addition, randomized controlled trials of smoking cessation interventions show that smokers with mental illness can achieve abstinence rates comparable with those of general population samples (Banham & Gilbody, 2010).

Given these contradictory findings, more research is needed into the association of mental health with smoking cessation to better understand causal relationships (Morrell & Cohen, 2006). However, much of what we know about the impact of smoking cessation on mental health comes from randomized controlled trials rather than naturalistic, observational studies, and cohort studies that can address the issue by comparing continuing smokers with those who stop are relatively rare (Ziedonis et al. 2008). Most large-scale studies in this area tend to be cross-sectional and retrospective (Mykletun et al. 2008; McClave et al. 2009) and prospective studies have often parochial and small sample sizes (Covey et al. 1997; Glassman et al. 2001; Gilbert et al. 2002), limiting the conclusions that can be drawn.

Thus, there is an expressed need for longitudinal data on this issue with regular follow-up in a sample that is representative of the general population of smokers. This paper reports on the impact of smoking cessation on self-reported depression and anxiety using data from ATTEMPT, the largest longitudinal, multinational general population study yet to be conducted on this topic. Specifically, we investigate the following questions: (1) What is the impact of short-term (<3 months) and longer-term (≥ 3 months) smoking cessation on the prevalence of depression and anxiety in a general population sample? (2) What is the impact of short- and longer-term smoking cessation on the prevalence of depression and anxiety among smokers with a history of these conditions?

A total of 45% of participants (n = 1640) completed both baseline and follow-up online questionnaires. Those lost to follow-up differed on a number of socio-economic and smoking but on only a few physical and mental health characteristics. Those lost to follow-up were slightly more likely to report a lifetime diagnosis of any mental health problem, in particular depression [χ² = 4.6, degrees of freedom (df) = 1, p = 0.032], but no other differences were apparent. Lifetime prevalence of depression and anxiety in the retained sample was 22.3% (95% CI 20.2–24.2%) and 27.4% (95% CI 25.1–29.4%), respectively. Overall, a third (37.5%, 95% CI 35.2–39.8%) reported any lifetime diagnosis (Table 1).

At 12 months, 7.5% (95% CI 6.3–8.9%) of smokers had stopped for at least 3 months and 9.7% (95% CI 8.3–11.2%) for less than 3 months. There were few differences in baseline variables according to smoking status at follow-up (Table 1). Those who were smokers at the 12-month follow-up had been more nicotine dependent (F = 10.5, df_between = 2, df_within = 1610, p < 0.001) and less likely to have previously made a quit attempt at baseline (χ² = 16.4, df = 2, p < 0.001) than recent ex-smokers. They also scored marginally lower on the EQ-5D than longer-term ex-smokers (F = 3.4, df_between = 2, df_within = 1603, p = 0.035).

Depression and anxiety as assessed in this cohort of smokers were common, with one in three reporting a lifetime diagnosis of either condition, and one in four experiencing recent symptoms. These estimates are broadly similar to previous studies confirming much higher incidence and prevalence rates among smokers than non-smokers (Perez-Stable et al. 1990; Breslau et al. 1991; Grant et al. 2004; Lawrence et al. 2009; McClave et al. 2009). In agreement with previous research (West & Hajek, 1997; McClave et al. 2009; Bolam et al. 2011), this study provides evidence that smoking cessation in the general population does not result in an increase in mental health problems and may be associated with a decrease in depression. Similar to a cross-sectional analysis, these effects appeared largely independent of the length of abstinence (Mykletun et al. 2008).

In contrast to some (Glassman et al. 1990, 2001; Covey et al. 1997) but not other studies (Haustein et al. 2002; Jamal et al. 2012), there was no evidence of an exacerbation of symptoms following smoking cessation among those with a history of mental health problems. This divergence may be due to a number of factors. This analysis provides a larger sample than most previous studies and includes participants from several countries. In addition, it is possible that the association of smoking cessation and deterioration in mental health may be a function of the severity of past mental health problems which was not assessed in the current study. However, even in studies reporting an increased risk of depressive episodes following cessation, rates were very low (Morrell & Cohen, 2006; Ziedonis et al. 2008), suggesting that this may be an issue for only a small proportion of smokers with a history of mental health problems.

In line with previous studies in general or patient populations, being married (Weissman et al. 1996; Frech & Williams, 2007) or in employment (Murphy & Athanasou, 1999) was independently associated with lower rates of depression and men were less likely than women to display anxiety symptoms (West & Hajek, 1997; Lewinsohn et al. 1998; Pigott, 1999; McClave et al. 2009). In addition, as shown previously, greater nicotine dependence was associated with anxiety (Goodwin et al. 2011), and improvement in general health was associated with better mental health (Wise & Taylor, 1990; Sherbourne et al. 1996; Patten, 2001; Ruo et al. 2003; Evans et al. 2005; Beard et al. 2007; Janney et al. 2008; Carek et al. 2011).

This study has some limitations. As data were collected online, smoking status and mental health were assessed by self-report rather than clinical assessment. However, self-report in surveys has been shown to be a valid indicator of both current smoking (Patrick et al. 1994) and mental health status (McChargue & Werth, 2007). While the use of prescription as an indicator is problematic, as prescription policies and practices vary between countries of included participants, several measures of mental health were used to increase reliability, yielding similar results, and country was included as a confounder in analysis. Moreover, prevalence estimates and observed associations with a range of sociodemographic variables replicate previous findings of studies using standard measures of mental health, further corroborating this approach. Whilst numerous covariates were included in the analysis, it is possible that inclusion of other uncontrolled variables, for instance, common vulnerability factors for both mental health and smoking such as impulsivity or neuroticism (Bienvenu et al. 2001; Hooten et al. 2005), could have altered results. In addition, self-selection cannot be excluded as an explanation for the findings. However, this problem could only be overcome using a randomized controlled design, which would be unethical, and sensitivity analysis showed that it is unlikely that self-selection alone can account for the observed associations. Lastly, given that this sample comprises Internet users, aged 35–64 years, who volunteered to participate, this may affect the generalizability of findings. However, previous analysis has shown that characteristics of this sample show high congruence with characteristics of equivalent national probability-based samples of the respective countries of participants (West et al. 2006). This study also had strengths. The longitudinal design allowed for an analysis of temporal associations in a large sample drawn from the general population across different countries, controlling for a multitude of confounders, which strengthens the generalizability of findings.

Our findings add substantially to a growing literature suggesting that smoking cessation may not only be beneficial for physical but also mental health in the general population and that it does not exacerbate symptoms of depression or anxiety among those with a history of these conditions. These outcomes may be explained by the adverse effects that chronic smoking has on neurophysiological substrates, being linked to changes in monoamine oxidase activity (Fowler et al. 1996) and levels of brain-derived neurotrophic factor (Kim et al. 2007) which have been implicated in the aetiology of psychopathology (Pintar & Breakefield, 1982; Sen et al. 2008). It has also been postulated that the frequent unpleasant withdrawal symptoms experienced by smokers may lead to the development and maintenance of mental health problems (Parrott, 2006). In this context it is important to reiterate that smokers with mental health problems are just as motivated to stop smoking as those in the general population and that smoking cessation interventions are equally effective in this group of smokers (Campion et al. 2008; Ziedonis et al. 2008). Thus smokers with and without current psychiatric comorbidities should be encouraged to stop smoking given the great benefits that smoking cessation provides.