Linden, David J. (2011). The Compass of Pleasure: How Our Brains Make Fatty Foods, Orgasm, Exercise, Marijuana, Generosity, Vodka, Learning, and Gambling Feel So Good. New York: Viking. 2011.
Scrivere opere di popular science non è affatto facile. Il mondo anglosassone ha una lunga tradizione, ma soprattutto ha un modo diverso di avvicinarsi al problema, tradito (come spesso accade) dal linguaggio: noi diciamo divulgazione scientifica (e l’immagine è quella dell’uomo di scienza o di cultura, dell’intellettuale insomma, che sparge i suoi tesori al popolo come un seminatore d’altri tempi, e poi chi è in grado di raccogliere le perle bene, e gli altri si arrangino), e loro fanno riferimento piuttosto al concetto di public understanding of science. Si sposta cioè l’accento sulle azioni e sulle politiche – ivi incluse le opere divulgative – atte a diffondere la comprensione degli avanzamenti delle scienze a tutta la popolazione: dove sono le persone che la compongono a giudicare in ultima istanza del successo delle politiche e delle azioni e i divulgatori a essere accountable del successo o dell’insuccesso delle politiche o delle singole azioni – ivi incluse, come dicevamo, le opere divulgative.
Il seminatore di Jean-François Millet
David Linden è uno scienziato (insegna neuroscienze alla Johns Hopkins di Baltimora) e i contenuti del suo libro sono davvero interessanti (riporterò alcune citazioni più avanti), ma si lascia prendere la mano dalla voglia di essere “leggero”, che si traduce nell’essere spiritoso a tutti i costi, con esiti non sempre convincenti. Insomma, cade negli stessi eccessi in cui – a mio parere (la mia recensione è qui) –cadeva Natalie Augier nel suo The Canon: soprattutto all’inizio di ogni capitolo, Linden si sente in dovere di condire di frizzi e lazzi il suo testo: come diceva Richard Dawkins della Augier (ma il suo voleva essere un complimento) ”Every sentence sparkles with wit and charm […] An intoxicating cocktail” (e dire che, dato il tema del libro, Linden di intossicazioni dovrebbe intendersi).
A parte questo difetto “letterario”, il lavoro di Linden è interessantissimo e, pur accumulando un grandissimo numero di informazioni nuove (almeno per me e, sospetto, per la maggior parte dei lettori: andate a leggere le citazioni che riporto alla fine per convincervene), ha un filo conduttore molto definito e una tesi di fondo unificante.
La tesi centrale del libro è che nel nostro cervello esista un circuito neurologico e un meccanismo unico (incentrato sul neurotrasmettitore dopamina) per il “piacere”, quale che ne sia la declinazione (da quello legato all’assunzione di sostanze psicoattive a quello sessuale, da quello legato al cibo a quello legato al gioco, fino al piacere “astratto” della conoscenza). Questa tesi smentisce molti luoghi comuni sul meccanismo delle dipendenze, ed è singolarmente vicino a quanto proposto il 12 aprile 2011 dall’American Society of Addiction Medicine.
Prima di lasciare la parola all’autore (con una presentazione radiofonica del libro e alcune citazioni), riporto la definizione di addiction proposta dall’ASAM (questo il link). Inutile sottolinearne l’importanza nel dibattito su “droghe” e legalizzazione.
Addiction is a primary, chronic disease of brain reward, motivation, memory and related circuitry. Addiction affects neurotransmission and interactions within reward structures of the brain, including the nucleus accumbens, anterior cingulate cortex, basal forebrain and amygdala, such that motivational hierarchies are altered and addictive behaviors, which may or may not include alcohol and other drug use, supplant healthy, self-care related behaviors. Addiction also affects neurotransmission and interactions between cortical and hippocampal circuits and brain reward structures, such that the memory of previous exposures to rewards (such as food, sex, alcohol and other drugs) leads to a biological and behavioral response to external cues, in turn triggering craving and/or engagement in addictive behaviors.
The neurobiology of addiction encompasses more than the neurochemistry of reward. The frontal cortex of the brain and underlying white matter connections between the frontal cortex and circuits of reward, motivation and memory are fundamental in the manifestations of altered impulse control, altered judgment, and the dysfunctional pursuit of rewards (which is often experienced by the affected person as a desire to “be normal”) seen in addiction–despite cumulative adverse consequences experienced from engagement in substance use and other addictive behaviors. The frontal lobes are important in inhibiting impulsivity and in assisting individuals to appropriately delay gratification. When persons with addiction manifest problems in deferring gratification, there is a neurological locus of these problems in the frontal cortex. Frontal lobe morphology, connectivity and functioning are still in the process of maturation during adolescence and young adulthood, and early exposure to substance use is another significant factor in the development of addiction. Many neuroscientists believe that developmental morphology is the basis that makes early-life exposure to substances such an important factor.
Genetic factors account for about half of the likelihood that an individual will develop addiction. Environmental factors interact with the person’s biology and affect the extent to which genetic factors exert their influence. Resiliencies the individual acquires (through parenting or later life experiences) can affect the extent to which genetic predispositions lead to the behavioral and other manifestations of addiction. Culture also plays a role in how addiction becomes actualized in persons with biological vulnerabilities to the development of addiction.
Other factors that can contribute to the appearance of addiction, leading to its characteristic bio-psycho-socio-spiritual manifestations, include:
- The presence of an underlying biological deficit in the function of reward circuits, such that drugs and behaviors which enhance reward function are preferred and sought as reinforcers;
- The repeated engagement in drug use or other addictive behaviors, causing neuroadaptation in motivational circuitry leading to impaired control over further drug use or engagement in addictive behaviors;
- Cognitive and affective distortions, which impair perceptions and compromise the ability to deal with feelings, resulting in significant self-deception;
- Disruption of healthy social supports and problems in interpersonal relationships which impact the development or impact of resiliencies;
- Exposure to trauma or stressors that overwhelm an individual’s coping abilities;
- Distortion in meaning, purpose and values that guide attitudes, thinking and behavior;
- Distortions in a person’s connection with self, with others and with the transcendent (referred to as God by many, the Higher Power by 12-steps groups, or higher consciousness by others); and
- The presence of co-occurring psychiatric disorders in persons who engage in substance use or other addictive behaviors.
Addiction is characterized by:
- Inability to consistently Abstain;
- Impairment in Behavioral control;
- Craving; or increased “hunger” for drugs or rewarding experiences;
- Diminished recognition of significant problems with one’s behaviors and interpersonal relationships; and
- A dysfunctional Emotional response.
The power of external cues to trigger craving and drug use, as well as to increase the frequency of engagement in other potentially addictive behaviors, is also a characteristic of addiction, with the hippocampus being important in memory of previous euphoric or dysphoric experiences, and with the amygdala being important in having motivation concentrate on selecting behaviors associated with these past experiences.
Although some believe that the difference between those who have addiction, and those who do not, is the quantity or frequency of alcohol/drug use, engagement in addictive behaviors (such as gambling or spending), or exposure to other external rewards (such as food or sex), a characteristic aspect of addiction is the qualitative way in which the individual responds to such exposures, stressors and environmental cues. A particularly pathological aspect of the way that persons with addiction pursue substance use or external rewards is that preoccupation with, obsession with and/or pursuit of rewards (e.g., alcohol and other drug use) persist despite the accumulation of adverse consequences. These manifestations can occur compulsively or impulsively, as a reflection of impaired control.
Persistent risk and/or recurrence of relapse, after periods of abstinence, is another fundamental feature of addiction. This can be triggered by exposure to rewarding substances and behaviors, by exposure to environmental cues to use, and by exposure to emotional stressors that trigger heightened activity in brain stress circuits.
In addiction there is a significant impairment in executive functioning, which manifests in problems with perception, learning, impulse control, compulsivity, and judgment. People with addiction often manifest a lower readiness to change their dysfunctional behaviors despite mounting concerns expressed by significant others in their lives; and display an apparent lack of appreciation of the magnitude of cumulative problems and complications. The still developing frontal lobes of adolescents may both compound these deficits in executive functioning and predispose youngsters to engage in “high risk” behaviors, including engaging in alcohol or other drug use. The profound drive or craving to use substances or engage in apparently rewarding behaviors, which is seen in many patients with addiction, underscores the compulsive or avolitional aspect of this disease. This is the connection with “powerlessness” over addiction and “unmanageability” of life, as is described in Step 1 of 12 Steps programs.
Addiction is more than a behavioral disorder. Features of addiction include aspects of a person’s behaviors, cognitions, emotions, and interactions with others, including a person’s ability to relate to members of their family, to members of their community, to their own psychological state, and to things that transcend their daily experience.
Behavioral manifestations and complications of addiction, primarily due to impaired control, can include:
- Excessive use and/or engagement in addictive behaviors, at higher frequencies and/or quantities than the person intended, often associated with a persistent desire for and unsuccessful attempts at behavioral control;
- Excessive time lost in substance use or recovering from the effects of substance use and/or engagement in addictive behaviors, with significant adverse impact on social and occupational functioning (e.g. the development of interpersonal relationship problems or the neglect of responsibilities at home, school or work);
- Continued use and/or engagement in addictive behaviors, despite the presence of persistent or recurrent physical or psychological problems which may have been caused or exacerbated by substance use and/or related addictive behaviors;
- A narrowing of the behavioral repertoire focusing on rewards that are part of addiction; and
- An apparent lack of ability and/or readiness to take consistent, ameliorative action despite recognition of problems.
Cognitive changes in addiction can include:
- Preoccupation with substance use;
- Altered evaluations of the relative benefits and detriments associated with drugs or rewarding behaviors; and
- The inaccurate belief that problems experienced in one’s life are attributable to other causes rather than being a predictable consequence of addiction.
Emotional changes in addiction can include:
- Increased anxiety, dysphoria and emotional pain;
- Increased sensitivity to stressors associated with the recruitment of brain stress systems, such that “things seem more stressful” as a result; and
- Difficulty in identifying feelings, distinguishing between feelings and the bodily sensations of emotional arousal, and describing feelings to other people (sometimes referred to as alexithymia).
The emotional aspects of addiction are quite complex. Some persons use alcohol or other drugs or pathologically pursue other rewards because they are seeking “positive reinforcement” or the creation of a positive emotional state (“euphoria”). Others pursue substance use or other rewards because they have experienced relief from negative emotional states (“dysphoria”), which constitutes “negative reinforcement.“ Beyond the initial experiences of reward and relief, there is a dysfunctional emotional state present in most cases of addiction that is associated with the persistence of engagement with addictive behaviors. The state of addiction is not the same as the state of intoxication. When anyone experiences mild intoxication through the use of alcohol or other drugs, or when one engages non-pathologically in potentially addictive behaviors such as gambling or eating, one may experience a “high”, felt as a “positive” emotional state associated with increased dopamine and opioid peptide activity in reward circuits. After such an experience, there is a neurochemical rebound, in which the reward function does not simply revert to baseline, but often drops below the original levels. This is usually not consciously perceptible by the individual and is not necessarily associated with functional impairments.
Over time, repeated experiences with substance use or addictive behaviors are not associated with ever increasing reward circuit activity and are not as subjectively rewarding. Once a person experiences withdrawal from drug use or comparable behaviors, there is an anxious, agitated, dysphoric and labile emotional experience, related to suboptimal reward and the recruitment of brain and hormonal stress systems, which is associated with withdrawal from virtually all pharmacological classes of addictive drugs. While tolerance develops to the “high,” tolerance does not develop to the emotional “low” associated with the cycle of intoxication and withdrawal. Thus, in addiction, persons repeatedly attempt to create a “high”–but what they mostly experience is a deeper and deeper “low.” While anyone may “want” to get “high”, those with addiction feel a “need” to use the addictive substance or engage in the addictive behavior in order to try to resolve their dysphoric emotional state or their physiological symptoms of withdrawal. Persons with addiction compulsively use even though it may not make them feel good, in some cases long after the pursuit of “rewards” is not actually pleasurable. Although people from any culture may choose to “get high” from one or another activity, it is important to appreciate that addiction is not solely a function of choice. Simply put, addiction is not a desired condition.
As addiction is a chronic disease, periods of relapse, which may interrupt spans of remission, are a common feature of addiction. It is also important to recognize that return to drug use or pathological pursuit of rewards is not inevitable.
Clinical interventions can be quite effective in altering the course of addiction. Close monitoring of the behaviors of the individual and contingency management, sometimes including behavioral consequences for relapse behaviors, can contribute to positive clinical outcomes. Engagement in health promotion activities which promote personal responsibility and accountability, connection with others, and personal growth also contribute to recovery. It is important to recognize that addiction can cause disability or premature death, especially when left untreated or treated inadequately.
The qualitative ways in which the brain and behavior respond to drug exposure and engagement in addictive behaviors are different at later stages of addiction than in earlier stages, indicating progression, which may not be overtly apparent. As is the case with other chronic diseases, the condition must be monitored and managed over time to:
- Decrease the frequency and intensity of relapses;
- Sustain periods of remission; and
- Optimize the person’s level of functioning during periods of remission.
In some cases of addiction, medication management can improve treatment outcomes. In most cases of addiction, the integration of psychosocial rehabilitation and ongoing care with evidence-based pharmacological therapy provides the best results. Chronic disease management is important for minimization of episodes of relapse and their impact. Treatment of addiction saves lives.
Addiction professionals and persons in recovery know the hope that is found in recovery. Recovery is available even to persons who may not at first be able to perceive this hope, especially when the focus is on linking the health consequences to the disease of addiction. As in other health conditions, self-management, with mutual support, is very important in recovery from addiction. Peer support such as that found in various “self-help” activities is beneficial in optimizing health status and functional outcomes in recovery.
Recovery from addiction is best achieved through a combination of self-management, mutual support, and professional care provided by trained and certified professionals.
Ecco la presentazione radiofonica:
Infine, alcune citazioni (sono costretto come di consueto a citare la posizione sul Kindle):
It’s important to note that even injecting heroin does not inevitably result in addiction. A recent study of drug use in the United States estimates that about 35 percent of all people who have tried injected heroin have become heroin addicts. While that’s a very high percentage relative to addiction rates of 22 percent for smoked or injected cocaine, about 8 percent for cannabis, and about 4 percent for alcohol, consider this shocking statistic: 80 percent of all the people who try cigarettes become addicted. 
[…] addiction is a form of learning. When someone uses a drug, associations are made between a particular act (injecting the drug or chewing the tobacco) and the pleasure that follows. 
Our homeostatic feeding control circuits make it very hard to lose a lot of weight and keep it off. As weight drops, fat mass decreases and leptin levels decline, triggering the biochemical cascade we just explored, producing signals that both reduce metabolic rate and produce a strong subconscious drive to eat. The more weight that is lost, the stronger the drive to eat will be and the greater the reduction in energy use. This is the sad but unavoidable truth that the multibillion-dollar-a-year diet industry doesn’t want you to know. 
[…] many animals (particularly males) are sexual opportunists and will attempt sexual contact with just about any species, live or dead. 
I don’t want a physical relationship.
I just want someone to fuck with my mind.
—personal ad in the L.A. Weekly (circa 1979) 
Deactivation of certain portions of the prefrontal cortex is also found in obsessive/compulsive disorder, which indeed shares some aspects with new love. [1458: non molto romantico ma non male]
Social psychologists who have interviewed people in long-term relationships find that the intense, initial phase of romantic love typically lasts from nine months to two years, to be replaced, in most couples, by a less intense form of loving companionship. 
Most states in the United States require a six-to twenty-four-month delay before granting a divorce, but anyone can get married immediately. One could make a case that to promote good, long-term marriages, the delay should be mandated on the front end. [1465: seriamente, mi sembra una proposta condivisibile]
Sex addiction is very real, and it takes a terrible toll. Sex addicts have the same trajectory as other addicts. They develop the same tolerance to the behavior, whereby more and more sex is necessary for achieving pleasure. Sex addicts have physical and psychological withdrawal symptoms if they can’t get the sex they need. And, most tellingly, they go through the same change in which liking gradually gives way to wanting. The sex that used to be a transcendent and energizing pleasure is now simply a necessary fix to face the day. [1669 – liking giving way to wanting, un quadro che richiama alla mente la parabola di qualche personalità anche pubblica]
One reasonable interpretation of these results is that we are hardwired to get a pleasure buzz from risky events. In this model it’s not that we need an early reward to like gambling. Rather, the uncertain nature of the payoff is pleasurable in its own right. Evolutionary scenarios have been proposed in which neural systems to drive risk-taking were adaptive, helping an animal beset with indecision to find more reliable predictors of important events. [1924: anche questo è uno spunto molto interessante, il rischio che dà piacere in sé]
[…] near misses promote continued gambling. In fact, there appears to be an optimal frequency of near misses to maximally extend slot machine gambling—about 30 percent 
[…] gamblers will bet more and continue gambling longer if they do have a personal role in these fundamentally random events. 
Video game play, a completely unnatural behavior divorced from intrinsic reward, activated the pleasure circuit to some degree in all subjects. Perhaps video games tap into some very general pleasure related to goal fulfillment and personal involvement. 
“Nature has placed mankind under the governance of two sovereign masters, pain and pleasure… . They govern us in all we do, in all we say, in all we think: every effort we can make to throw off our subjection, will serve but to demonstrate and confirm it.”[Jeremy Bentham. An Introduction to the Principles of Morals and Legislation. 1789] The accumulating neurobiological evidence indicates that Bentham was only half correct. Pleasure is indeed one compass of our mental function, guiding us toward both virtues and vices, and pain is another. However, we now have reason to believe that they are not two ends of a continuum. The opposite of pleasure isn’t pain; rather, just as the opposite of love is not hate but indifference, the opposite of pleasure is not pain but ennui—a lack of interest in sensation and experience. 
n the lexicon of cognitive neuroscience, both pleasure and pain indicate salience, that is, experience that is potentially important and thereby deserving of attention. Emotion is the currency of salience, and both positive emotions like euphoria and love and negative emotions like fear, anger, and disgust signal events that we must not ignore. 
[…] voxel (a three-dimensional pixel) […] [2184: giusto perché io non conoscevo il termine]
[…] both the spatial and the temporal resolution […] [2185: detto efficacemente]
[…] is information about the future pleasurable in and of itself? 
To my thinking, this experiment is revolutionary. It suggests that something utterly useless and abstract— knowing merely for the sake of knowing— can engage the pleasure/reward circuitry. […] This experiment suggests that ideas are like addictive drugs. As we have seen, certain psychoactive drugs co-opt the pleasure circuit to engage pleasurable feelings normally triggered by food, sex, and so on. In our recent evolutionary lineage (including primates and probably cetaceans), abstract mental constructs have become able to engage the pleasure circuitry as well, a phenomenon that has reached its fullest expression in our own species. The neuroscientist Read Montague, weaving together several strands of thought in cognitive neuroscience from a number of investigators, calls the human ability to take pleasure in abstract ideas a “superpower”28 and I’m inclined to agree with him. From this perspective, human ideas can even directly oppose our most basic pleasure drives. [2363-2367]
[…] exploratory behavior, a correlate of addiction.