The pathway responsible for the most reinforcing characteristics of addictive substances, in both the general and bariatric patient population, is the mesolimbic dopamine system [29, 30]. This pathway includes dopaminergic neurons in the ventral tegmental area (VTA) of the midbrain and their targets in the limbic forebrain, especially the nucleus accumbens (NAc). Eventually, neuronal signaling from the NAc reaches the frontal cortex, which is heavily involved in the decision-making process. Various drugs of addiction, regardless of its distinct mechanism of action, converge on the mesolimbic pathway and increase dopaminergic transmission to the NAc after acute administration. They can do so either directly, like cocaine, or indirectly, in the case of opioids [29].

In addiction to drugs of abuse, the rewarding effects of food have also been associated with dopamine (DA) release [31]. The mesolimbic pathway, specifically DA effects in the NAc, has been associated with the motivational processes related to appetite [32] and the drive to eat [33, 34]. The role of DA regulation in obesity is evident through research demonstrating an association between the Taq I A allele and reduced DA dopamine-2 (D2) receptors in brain regions [35]. Based on these findings, researchers purport that obese patients with the Taq I A allele may be predisposed to using food to compensate for this reduction in DA D2 receptors and to stimulate DA activity.

Additional important brain regions that interact with the mesolimbic pathway in substance use disorders include the amygdala, hippocampus, and hypothalamus, among many others. In contrast to drugs of abuse, the relationship between the mesolimbic pathway and hypothalamus in food consumption is mediated through several peripheral signaling pathways involving peptides and hormones, such as leptin, insulin, and cholecystokinin [36]. These peripheral signaling pathways are more specific to obesity and food regulation, whereas drugs of abuse rely on direct effects on mesolimbic structures and the reward system [36, 37].

Moreover, chronic drug use is associated with additional adaptations in dopamine function via both dopamine dependent and independent circuits. Chronic exposure of many addictive substances causes an impaired dopamine signaling system due to the body’s attempt to adapt to repeated drug activation (i.e., drug tolerance). Specifically, baseline levels of dopamine are reduced, and normal rewarding stimuli may be less effective at eliciting typical increases in DA transmission. When the person with addiction discontinues substance use, the body can no longer maintain homeostasis, thus resulting in symptoms of withdrawal. Additional disruptions in the corticotropin-releasing factor (CRF) syste m can also contribute to the negative affective symptoms during substance withdrawal [29].

Balancing behaviors that provide a reward immediately versus behaviors that can provide an advantage later is critical for human adaptive functioning. The “now versus later” model has been used to describe how both addictions and obesity are based on an excessive emphasis of obtaining immediate reward in lieu of choosing actions that promote long-term gains. The circuit responsible for now versus later decision-making involves many of the same anatomical structures of the mesolimbic pathway [37]. According to this model, different signaling patterns of DA can favor the now versus later processes. Specifically, phasic signaling of dopamine in the reward pathway signals “now,” whereas tonic signaling in control circuits connected to the reward pathways favors “later.” Areas of the brain that mediate “now” signaling include the ventromedial prefrontal cortex and the NAc. Areas of the brain that mediate the “later” signaling include the medial prefrontal cortex, dorsolateral prefrontal cortex (DLPFC) , anterior cingulate cortex (ACC) , and the caudate [37]. Interestingly, these areas reduce their baseline activity to the body’s attempt to adapt to chronic drug exposure. This results in a dysfunctional decision-making circuit in individuals with addictions leading to “hypofrontality,” defined by impulsive and compulsive substance use behaviors.

This “now versus later” model and resulting impulsive and compulsive behaviors are applicable to obesity. Studies showing reductions in D2 receptor in the striatum (including the NAc) in obese animal models and associated decreases in activity in various regions of the frontal lobe provide further support for the impulsivity and compulsivity observed in eating in some obese patients [38, 39]. The result of these shared pathways between obesity and drug addiction has generated much discussion on the conceptualizing of obesity as “food addiction ”; however, much of the evidence for food addiction is based on rat models, and we have yet to identify specific food substances or molecules that cause addiction to date [40]. Despite these parallels between drug addiction and obesity neurobiological pathways, clinicians should not be preoccupied with justifying food addiction nomenclature and should instead be using the understanding of these shared pathways to develop potential therapeutic alternatives for both substance use and obesity .

Ghrelin is an endogenous molecule that plays an important role in long-term weight regulation. Through several pathways, ghrelin can bind to growth hormone secretagogue receptors in the hypothalamus, which leads to signaling cascades leading to increased food intake [41]. Although plasma ghrelin is elevated in individuals undergoing long-term diets, plasma ghrelin is markedly suppressed following bariatric surgery, and this change in ghrelin is hypothesized to contribute to sustaining weight loss after bariatric surgery [42, 43].

Interestingly, there is some research that ghrelin could also impact the reward system pathways. It is suggested that ghrelin acts on the mesolimbic reward circuit via cholinergic afferents extending to the VTA and enhancing dopamine effects in the brain [44, 45]. Moreover, data from animal models has not shown reproducible results regarding the effects of ghrelin on post-surgery alcohol use [46–48]. Therefore, it is unclear whether decreases in ghrelin post-bariatric surgery could impact the frequency of addictive behavior and substance use in post-bariatric surgery patients.

Leptin , an appetite regulating peptide responsible for satiety, is produced by adipocytes and regulates energy balance by suppressing hunger [49]. Patients with obesity can develop leptin resistance over time, which impairs satiety signaling in response to high-energy stores [50]. Few studies have identified a positive correlation between leptin levels and food-cued brain activations in the mesolimbic area [51, 52]. Thus, the creation of a leptin-resistant state may result in elevations in leptin resulting in altered homeostatic regulation of reward pathways related to food [52].

As noted earlier in this chapter, RYGB has been associated with increased rates of alcohol use disorders post-bariatric surgery [18]. Researchers postulate that increases in alcohol sensitivity and a change in ethanol pharmacodynamics following RYGB may increase alcohol’s reinforcing effects, resulting in the observed increase in AUD rates after bariatric surgery [53].

Post-RYGB patients reach higher peak blood alcohol levels more rapidly than age- and BMI-matched controls ingesting the same amount of ethanol and take longer to return to baseline [54]. There are two potential reasons for this phenomenon. Firstly, post-RYGB patients have rapid emptying of liquids from the gastric pouch into the jejunum, thus resulting in faster speed of absorption. Secondly, the portion of the stomach that secretes alcohol dehydrogenase, which metabolizes alcohol, is bypassed by RYGB [55]. The changes of the effect of alcohol on post-RYGB individuals could make alcohol more reinforcing and an individual more susceptible to AUD post-bariatric surgery .

Data on metabolism of other substances is lacking; however, there is some evidence that these substances can be metabolized in a way that enhances abuse liability in the postoperative phase. Recent data suggests that the propensity for substance abuse may be increased with two substances, namely, opioid pain medications and benzodiazepines [16]. Opioids may also provide benefits to RYGB patients post-surgery because of their effects on the gastrointestinal (GI) tract . Specifically, opioids decrease gastric motility and increase intestinal transit time, which could mitigate adverse effects associated with “dumping syndrome,” a post-RYGB condition characterized by dizziness, nausea, cramps, bloating, diarrhea, chills, and hot flashes, particularly following consumption of sweet foods. Benzodiazepines may have abuse liability because they are rapidly absorbed in the GI tract; the exact nature of benzodiazepine absorption among RYGB patients is unknown [16].

There is conflicting evidence regarding substance use and its impact on weight loss after bariatric surgery [56]. There is some evidence that post-bariatric surgery patients meeting criteria for substance use disorders experienced a lower percentage of total weight loss than those who did not have substance use disorders [23]. Studies have also shown that patients with presurgery substance use who participated in substance use treatment programs before surgery were more likely than patients without substance use disorders to have sustained weight loss postoperatively [57, 58]. It should be noted that patients participating in substance use disorder programs presurgery were more likely to have higher depressive symptoms post-surgery compared to controls [57]. Despite this conflicting data on postoperative substance use and weight loss, the onset of substance use disorders after surgery has been linked to worse mental health outcomes, such as depression and eating psychopathology [59].

In addition to the impact of substance use disorders on patients’ quality of life and mental health, certain substances can have detrimental effects on surgical outcomes. Both nicotine use, specifically cigarette smoking, and alcohol use perioperatively have been associated with increased risk of postoperative ulcers in gastric bypass patients [60]. Moreover, cigarette smoking has been associated with increased incidence of prolonged intubation, re-intubation, sepsis, shock, and length of stay after laparoscopic bariatric surgery [61].

After bariatric surgery, patients who experience substance use relapse can suffer additional medical complications. Given that post-bariatric surgery patients are already at risk of thiamine deficiency and in severe cases, Wernicke encephalopathy , independent of alcohol use, patients who experience a relapse of their alcohol use disorder after surgery are likely to be at increased risks of these nutritional complications [62, 63]. Moreover, opioid use after bariatric surgery can exacerbate constipation immediately after surgery, resulting in increased pain and discomfort. Therefore, knowledge regarding substance-related bariatric surgery complications is essential in effectively counseling patients on potential risks of substance use postoperatively.

The CAGE is a brief questionnaire that was developed by Dr. John A. Ewing in 1970 as a short clinical tool to screen for problem drinking in a patient. It consists of four simple questions [65] (see Table 11.2). Two “yes” responses indicate that the possibility of alcoholism should be investigated further. There have been many studies that validated its use [65–67]. Some studies suggest that positive CAGE testing is associated with a 91–93 % sensitivity for identification of excessive drinking and alcoholism [66, 67]. The advantages of the CAGE are that it is a simple screening tool that is easy to administer even in time-constrained settings. However, other studies suggest that the CAGE is more suitable for screening for advanced alcoholism but are less sensitive in detecting those with mild drinking problems, who actually form a larger proportion of the general population [68].

The AUDIT is a 10-item instrument developed by a six country collaborative project led by the World Health Organization (WHO) to assess alcohol use and alcohol-related consequences and has well-established validity and reliability [68, 69]. A total score (range: 0–40) is calculated using this 10-item questionnaire, each of which is scored from 0 to 4 points, with a higher score reflecting greater severity of AUD (please see the appendix for the copy of an AUDIT questionnaire). Additionally, subsets of items cover different domains of consumption, such as consumption at a hazardous level, symptoms of alcohol dependence, and alcohol-related harm to self and others. These questions were selected from a larger 150-item assessment schedule, which was administered to 1888 persons attending various primary care facilities. They were selected on the basis of their representativeness for these conceptual domains and their perceived usefulness for intervention. Among those diagnosed as having hazardous or harmful alcohol use, 92 % had an AUDIT of 8 or more and 94 % of those with nonhazardous drinking behaviors had scores of less than 8. AUDIT is also a simple method of early detection of harmful drinking behaviors meant for the primary health care setting. A study comparing the AUDIT and the CAGE suggests that AUDIT was superior to the CAGE in the identification of patients with heavy drinking or active alcohol abuse or dependence [70].

The AUDIT has been used to stratify patients in terms of risk in bariatric surgery programs [71]. Positive AUDIT scales for hazardous alcohol use have been used to prompt further investigation, such as additional toxicology screening for additional substances. Studies comparing the AUDIT to structured psychiatric interview have also shown that the AUDIT results in higher rates of alcohol use problems and underscores the need for further clinical assessment to elucidate the presence of an AUD [15].

Due to concerning data regarding the increased risk of developing substance use disorders, namely, alcohol use disorder, after surgery, it is important to discuss these risks and addiction prevention with bariatric surgery candidates early in the presurgery assessment process [71].

Patient education regarding alcohol use after bariatric surgery should include specific information regarding changes in alcohol pharmacokinetics. For example, specific to alcohol, patients should be given information that alcohol might be much more intoxicating after surgery and that a single glass of wine could potentially make the serum alcohol concentration above the legal driving limit in a post-bariatric patient [72]. As well, some bariatric patients can show atypical symptoms of intoxication (e.g., dizziness), and it can take a much longer time for a post-bariatric surgery patient to return to sobriety. The adverse effects of alcohol and other substances of abuse also need to be included in the discussion, as well as the fact that bariatric surgery patients might be at increased risk of alcohol-related problems after surgery. Both patients and families should be given information on available community resources should they feel they need help with addiction after bariatric surgery.

Ashton and colleagues reported the benefit of their alcohol use patient education groups in bariatric surgery candidates [73]. In their study, patients with a history of a substance use disorder or at-risk substance use were referred to a single 90-min group education session. After attending this session, patients reported improved knowledge regarding the negative effects of substance use post-surgery and increased healthy coping strategies. Furthermore, patients reported being more likely to stop drinking after the education group intervention. Therefore, early identification of at risk patients for alcohol use problems presurgery can facilitate patient engagement in presurgery alcohol use interventions; however, further research is needed to determine long-term efficacy of these programs in supporting sustained weight loss in patients with severe obesity .

Motivational interviewing (MI) is both a mindset and a treatment philosophy used to help people evoke their own intrinsic motivation when they experience ambivalence about changing a particular behavior [74]. The theoretical underpinning of MI is such that without motivation, knowledge provided to the patient alone will not generate a change in behavior. As well, only when individuals believe they have a problem, will they be motivated to change more effectively [75, 76]. Motivational interviewing as an intervention for severe obesity management is summarized in a chapter later in this book (see Chap. 20). A large body of research has demonstrated the efficacy of motivational interviewing in reducing drug use and other addictive behaviors including risky sexual behaviors and diet/exercise [77, 78]. Treatment with motivational interviewing both during the pre- and post-bariatric surgery should be offered if available to patients who are identified as being at risk for alcohol or other substance-related disorders .

CBT/relapse prevention is a therapeutic method based on the approach of CBT, which are grounded in the principles of operant conditioning and social learning theories. The goals of CBT/relapse prevention include the identification of drug use within the context of its antecedents and consequences and the generation of effective behavioral alternatives that facilitate one’s ability to stay away from the substance. This therapeutic intervention includes and is not limited to relapse analysis (analyzing high-risk situations for relapse and early warning signs of relapse), drug refusal skill development, affect management skill enhancement, and the identification of cognitive distortions towards the substance of use. There is a large amount of evidence to support the use of cognitive behavioral therapy in the treatment of alcohol use disorders and other substance use disorders [79–81].

A 12-step program is a set of spiritual principles outlining the method to overcome addictive behaviors and originated as alcoholics anonymous (AA) for alcohol use problems. Currently, 12-step programs exist for multiple substances including overeaters anonymous for obesity [82]. Approximately, 9 % of the US general population has attended an AA meeting in their lifetime [83].

The original 12 steps focused on the admission of having a substance use problem and surrendering the hope for recovery through the recognition of the loss of control. It frequently made references to a greater power that could restore balance in the person’s lives and also contained action items to be completed by the recovering participant, such as making amends to friends and family that may have been previously hurt [84]. Since then, the wording of these steps has been altered to remove gender-biased language, and there are secular groups that omit references to a deity or deities. Auxiliary groups to AA, such as Al-Anon and Nar-Anon, are available for the family and caregivers of people suffering from substance use disorders .

There are a variety of other psychosocial treatment modalities, including brief intervention, contingency management/community reinforcement, psychodynamic/interpersonal therapy, drug counseling, family therapy, network therapy, and residential treatment. These modalities should be considered based on weight loss and bariatric surgery program’s availability of such interventions and resources. Ideally, a combination of multiple modalities can support patients in managing addictive disorders in the context of severe obesity.

Limited literature on the efficacy of psychosocial interventions for addictive disorders exists in patients with severe obesity or undergoing bariatric surgery. As a result, current psychosocial management of addictive disorders is extrapolated from literature from general addiction literature.