In a paper that was recently published (open access) in Neuroethics, Dr. Hannah Maslen, Prof. Julian Savulescu, and I provide an ethical analysis of the use of Deep Brain Stimulation (DBS) in the treatment of treatment-refractory anorexia nervosa (AN). In this post, I shall briefly summarise the first half of this paper, in which we explain why the use of DBS in the treatment of AN raises new ethical questions, and describe the different mechanisms that DBS might operate upon.
Deep brain stimulation is an invasive neurological procedure that has been successfully used to ameliorate motor symptoms associated with neurological conditions such as Parkinson’s disease. The procedure involves the implantation of electrodes into a targeted area of the patient’s brain, through which an electrical impulse may be transmitted. Stimulation of the targeted brain area occurs when the physician activates a pulse generator, which is normally implanted subcutaneously below the patient’s clavicle.
Following its success in the treatment of Parkinson’s disease, DBS has been increasingly considered in the treatment of a range of psychiatric conditions. In the past couple of years, a number of case studies have suggested that DBS might be effectively used in the treatment of anorexia nervosa [AN]. This is highly significant for two reasons. First, other methods employed in the treatment of AN, such as cognitive-behavioural therapy (CBT) and ‘talk therapy’ have only limited effectiveness. Second, AN is a highly dangerous disorder; indeed, it has the highest mortality rate of any psychiatric disorder in adolescence (NICE Guidelines 2004, 7).
How is DBS different from other treatment methods used in the context of AN? One intuitive difference between DBS and other commonly used treatment methods in this context (such as CBT) is that DBS changes the subject’s thought patterns by directly altering brain function. In contrast, CBT can be understood to only indirectly alter the subject’s brain function, in so far as such changes only occur following the change in thought patterns that CBT seeks to evince. We may thus describe DBS as a direct brain intervention (Focquaert and Schermer 2015).
In view of Levy’s parity principle (Levy 2007), the mere fact that an intervention is direct rather than indirect in this sense is not a sufficient basis for claiming that it is morally problematic. We might also note that pharmacological interventions and other neurosurgical interventions that might be used in psychiatry are direct in this sense. However, DBS differs from other existing direct treatment methods in AN for a number of reasons. First, the degree of stimulation can be precisely adjusted to the needs of the individual patient, and it is also reversible; as well as deactivating stimulation for a period of time, the implanted pulse generator can be surgically removed. Second, and more importantly, DBS allows for more precise and selective targeting of neuronal activation than other existing direct interventions.
This latter aspect of DBS raises an important question for how it should be implemented in the treatment of AN, since the effects of DBS will depend upon the brain area that is stimulated. In the remainder of the post, I shall describe three mechanisms that DBS might plausibly operate on in the treatment of AN, and indicate some of the ethical questions that each target raises. This discussion is necessarily sketchy due to considerations of length; for further detail, please see the full paper.
1. Modification of Aberrant Reward Processing
In some case reports, DBS has been used to target the Nucleus Accumbens of patients suffering from AN, and has had positive outcomes in terms of weight recovery and other pathologies (Park, Godier, and Cowdrey 2014). This is interesting because the Nucleus Accumbens is part of the Ventral Striatum, which is directly implicated in reward processing. Accordingly, the success of DBS targeted at this site suggests that DBS might be used to modify aberrant reward processing in sufferers of AN; it might even be viewed as serving to increase the desirability of food to the patient, or their motivation to eat.
However, things are perhaps not as simple as this. It is important to draw a theoretical (and neurologically supported) distinction here between ‘wanting’ and ‘liking, whereby ‘wanting’ denotes motivational salience, whilst ‘liking’ denotes pleasure taken in an object. Furthermore, wanting and liking can occur at a conscious (explicit) or subconscious (implicit) level. Usually, wanting and liking work in concert; we tend to want the things we like. Since I like the taste of wine, I feel the motivational pull of drinking wine. However, on one view, wanting and liking cease to work in concert in AN, and there can be conflicts between the patient’s explicit and implicit wants and likes. It may be that the patient implicitly wants food in the absence of explicit liking (Park, Godier, and Cowdrey 2014).
With this in mind, it is too simplistic to say that DBS would impose a desire for food, since the use of the term ‘desire’ can lead to conflations of wanting and liking, and implicit and explicit drives. Rather than considering whether the positive outcomes following DBS of areas associated with reward processing suggests that the procedure ‘imposes a desire for food’, we should consider the effects it has on implicit and/or explicit drives, and on liking and wanting. Does DBS here make an explicit want implicit? If so, then stimulation might in some cases be understood to reveal to the patient what she ‘really wants’ at a higher-order level, which in turn could be understood to facilitate her autonomy on many accounts of that concept. Alternatively, DBS of this area might be construed as imposing a liking for food. This might put the patient at risk of psychological harm if this ‘liking’ is incongruous with her wants. Moreover, on certain rationalist accounts of autonomy, even if DBS amplifies the patient’s liking of food in accordance with an explicit want, this may undermine her autonomy if this incongruous with her negative evaluation of eating; she will like and want to do something that she thinks she has very strong reasons to refrain from doing.
2. Increased Comparative Control Over The Drive Towards Compulsive Behaviour
Alternatively, it might be argued that AN is characterised by the patient’s aberrant control over a compulsive behaviour. On this view, it might be claimed that AN patients suffer from hyperactive weight-loss compulsion, where weight-loss behaviours that may have started out as goal-driven, have themselves become rewarding, in abstraction from the behaviour’s effects on weight. These behaviours become habitual and very difficult to resist, driven by an overwhelmingly strong motivational desire. DBS might plausibly be used to normalise aberrant control over compulsive desires by targeting the cortico-striatal thalamic circuit (CSTC) (Park, Godier, and Cowdrey 2014).
DBS could plausibly combat this damaging habitual behaviour either by reducing the patient’s compulsive want to refrain from eating, or by increasing their top-down control over the want without actually reducing the want itself. Again the effect of DBS would depend upon which neural components were targeted.
Would reducing the patient’s compulsive want increase her autonomy? This would plausibly be the case if the want were in conflict with the patient’s higher order volitions, desires, or evaluations. However, if the patient actually identifies with the compulsive desire, or positively evaluates the pursuit of thinness, then reducing the compulsive want would not necessarily serve to increase her autonomy on many plausible accounts. The strength of her pathologically compulsive desire is helping her to get what she really wants. In contrast, it seems that the increase of top-down control would serve to enhance the patient’s autonomy regardless of her higher-order desires or evaluations; it would be up to the agent whether or not to exert this control over her strong desires.
2. Regulation of Aversive Mood and Affect
AN might also be construed as a disorder of emotional processing, and DBS might be applied to brain areas which play a role in the modulation of emotional states such as the subcallosal cingulate Some studies suggest that the stimulation of this area may indirectly lead to increased body weight since improved mood may enhance uptake of conventional indirect treatments for AN (Lipsman et al. 2013)..
Regulation of aversive mood and affect does not directly affect the patient’s drives and desires, although it may do so indirectly. As such, the potential threat to autonomy is arguably reduced, in so far as the patient may psychologically mediate the indirect changes to her motivational desires following the induced affective changes. However, we might be concerned that changes to the patient’s mood may pose a threat to their feeling of authenticity, of feeling that they are living in accordance with their “true self”. One’s emotional states are often thought to be central to one’s sense of identity, of ‘who you are’. Are affective states induced via a direct brain intervention likely to be considered authentic to the agent? Should this matter? Such concerns will be familiar to readers who have followed the neuroethical debate surrounding human enhancement drugs. However, we should note that the alteration of affect in the context of AN is likely to be more nuanced by virtue of the fact that many AN patients report that their sense identity is importantly tied to their condition (Tan et al. 2007).
Accordingly, there are a number of ways in which DBS might be implemented in the treatment of AN, each of which raise different concerns about the patient’s autonomy and authenticity. I have not had space here to discuss different accounts of these latter concepts, and the implications that different accounts might have for the above concerns. Moreover, I have not addressed the question of how much we should care about patient autonomy or authenticity in the context of treatment-refractory anorexia, or whether such patients are competent to make autonomous decisions. I hope to address these issues in next week’s post.
References
Focquaert, Farah, and Maartje Schermer. 2015. “Moral Enhancement: Do Means Matter Morally?” Neuroethics 8 (2): 139–51.
Levy, Neil. 2007. Neuroethics. Cambridge: Cambridge University Press.
Lipsman, Nir, D. Blake Woodside, Peter Giacobbe, Clement Hamani, Jacqueline C. Carter, Sarah Jane Norwood, Kalam Sutandar, et al. 2013. “Subcallosal Cingulate Deep Brain Stimulation for Treatment-Refractory Anorexia Nervosa: A Phase 1 Pilot Trial.” Lancet (London, England) 381 (9875): 1361–70.
NICE Guidelines. 2004. “Eating Disorders Core Interventions in the Treatment and Management of Anorexia Nervosa, Bulimia Nervosa, and Related Eating Disorders.”
Park, Rebecca J., Lauren R. Godier, and Felicity A. Cowdrey. 2014. “Hungry for Reward: How Can Neuroscience Inform the Development of Treatment for Anorexia Nervosa?” Behaviour Research and Therapy 62 (November): 47–59.
Tan, Jacinta, Anne Stewart, Ray Fitzpatrick, and R. A. Hope. 2007. “Competence to Make Treatment Decisions in Anorexia Nervosa: Thinking Processes and Values.” Philosophy, Psychiatry, & Psychology 13 (4).
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