This is the first study to examine the comorbidity between alcohol and drug use disorders and AN by investigating the prevalence of SUD across AN subtypes, by comparing individuals who report binge eating in the underweight state versus those who develop binge eating at normal weight (i.e., not during episodes of AN), and across the entire sample stratified by the presence of binge eating and purging. Our findings indicate that: (1) SUD are most common among individuals with the ANBN subtype; (2) those who endorse purging behavior have higher rates of SUD compared to those who do not report purging; and (3) prevalence of drug use differs across binge eating status.
While our observed prevalence of SUD was higher than other AN samples,3, 9, 10, 23–25
which could be explained by definitional issues (i.e., we used a subthreshold, broader definition for SUD) or cross-cultural differences in SUD — our findings are consistent with several previous studies reporting that individuals with BN or with a history of bulimic symptoms during the course of AN were more likely to report SUD compared to those with RAN.8–11, 26–30
Specifically, in the current study, ANBN participants reported significantly higher levels of drug abuse/dependence than all other AN subtypes, while the RAN group had the lowest prevalence of drug abuse/dependence. This finding supports previous research suggesting that ratio of alcohol abuse/dependence across a sample of inpatient females with BN, ANBN, and RAN was 9:5:1,10
as well as findings from a community sample with Canadian adolescents reporting that binge eaters, particularly those who compensated, were more likely to report substance use.26
Likewise, dietary restraint and bulimic symptoms in Latina adolescents were positively correlated with alcohol, tobacco and illicit drug use.29
Our finding that greater substance use occurred in the purging group suggests that there may be meaningful characteristics associated with classification based on the presence or absence of purging. 12, 13
We also examined the relation of drug category across AN subtypes and found differences in the prevalence of the drug use category across AN subtypes. In the current study, the most frequently used drug was cannabis, followed by hallucinogens. These findings support previous research suggesting that greater pathological eating behavior is associated with not just alcohol and tobacco but also marijuana and other hard substances.26
The prevalence of cannabis use being the highest is consistent with population norms 31
and previous research suggesting that cannabis is the most frequently reported illicit drug among those with restricting and binge eating/purging symptomatology. 8–11
Our findings are not surprising given that epidemiological data indicate that cannabis is the most frequently reported illicit drug.31
What is surprising is that results from this study challenge the commonly held belief that individuals with RAN report lower levels of drug use.3
Nonetheless it is important to note that the prevalence reported in this paper may partly reflect normative experimentation with alcohol, tobacco, and illicit substances, particularly during adolescence and young adulthood. Therefore, results should be interpreted with caution. Unexpectedly, hallucinogen use was the second most commonly reported substance used among those with RAN. While little research exists on the relation between hallucinogen use and eating disorder symptoms, it is possible that the appetite-suppressing effect of hallucinogens, 32
along with the physiological response of changes in perceptions and thoughts which might allow one to “escape” the anxiety associated with the eating disorder, are motivating factors among those who restrict food intake. These motivations may be further encouraged given the availability of some hallucinogens on the internet.33
Elaborating on the association between SUD and AN within the current study, findings also suggest that a higher prevalence of individuals in the BAN and ANBN groups reported greater sedative, stimulant and cocaine use compared to those in the RAN group, with those in the ANBN reporting the greatest use. This finding supports previous research suggesting that cocaine and amphetamine use is greater primarily in individuals with the binge eating/purging subtype of AN.30
The use of stimulants and cocaine among the BAN and ANBN groups may be due to the appetite suppressant effects these drugs may have; thus, their use may be an effort to avoid the consequences of overeating. It has also been hypothesized that an association between SUD and eating disorders reflects an underlying influence of personality traits such as heightened impulsivity.34, 35
Our study was not, however, designed to identify mechanisms underlying the relation between SUD and binge eating/purging AN.
Of final note, our findings suggest that binge eating was related to substance use under certain conditions. Risk for alcohol abuse/dependence and drug abuse/dependence was higher in those who reported binge eating at low weight relative to those who did not binge eat, but differences did not emerge between those who binge ate at low weight versus binge ate only after weight restoration. These findings are inconsistent with previous research suggesting that risk for excessive alcohol consumption is higher in individuals who exhibit binge eating at low weight compared to those who develop binge eating after restoration of normal weight.6
This inconsistency could be due to differences across study design (i.e., longitudinal vs. cross-sectional), and to our smaller sample size. It has also been suggested that reward hypersensitivity may be a common vulnerability factor for both hazardous drinking and disordered eating.36–38
Limitations to our study must be considered. First, participants are primarily of European ancestry and therefore cannot be generalized to other ancestry groups or to males. Second, a healthy comparison group was not available for comparison and our primary interest was examining differences in SUD across the AN subtypes. Third, we did not make distinctions between current and lifetime diagnoses for AN. It is possible that differences in substance use patterns would have emerged had such information been available. Fourth, substance use data also focused on lifetime use only, not frequency and duration of use which could differentiate AN subgroups in unique ways. Additionally, the categorization of drug use is a potential limitation in that the “drug use” group included those who used a substance at least twice but not enough to meet criteria for abuse/dependence. Thus, results related to the “drug use” group need to be interpreted given this knowledge. Finally, causal conclusions pertaining to the development of either eating disorders or SUD cannot be discussed. The nature of any casual relation between AN and SUD is unknown, thus we are unable to ascertain if the eating disorder lead to SUD or if the SUD lead to eating disorder symptomatology. Further, we are not aware if certain substances were specifically used for weight-loss. Additional unexamined factors may have influenced findings. Of particular relevance are data suggesting that depression, negative affect, and anxiety are associated with eating disorders and SUD.39, 40
Future studies should consider depression, negative affect, and anxiety as each relates to the comorbidity of eating disorders and SUD.
Conclusions and Implications
Results from this and other studies highlight the need to assess alcohol and drug use behavior when screening and treating individuals with AN, particularly those with bulimic symptomatology. Our findings support previous research indicating that individuals with lifetime diagnoses of both AN and BN (ANBN group in the current analysis) and those who engage in bulimic behaviors report more alcohol abuse/dependence and drug abuse/dependence than those who only engage in restricting behaviors. These findings are of clinical importance because prior research indicates that individuals presenting with both an eating disorder and SUD may be at heightened risk for physical health complications, including increased lethality,41
and additional psychological comorbidities.7
Given the comorbidity between AN and SUD, particularly among those with ANBN and BAN, it would appear prudent and necessary to combine prevention and treatment efforts in order to better avert the emergence or advancement of these disorders.