Long established as the preeminent source in its field, the eagerly anticipated fifth edition of Dr Stahl's essential textbook of psychopharmacology is here! With its use of icons and figures that form Dr Stahl's unique 'visual language', the book is the single most readable source of information on disease and drug mechanisms for all students and mental health professionals seeking to understand and utilize current therapeutics, and to anticipate the future for novel medications. Every aspect of the book has been updated, with the clarity of explanation that only Dr Stahl can bring.
Impulsivity, Compulsivity, and Addiction
Impulsivity and compulsivity are symptoms that cut across many psychiatric disorders. Some conditions with impulsivity as a prominent feature have already been discussed, including mania (Chapter 4); attention deficit hyperactivity disorder (ADHD; Chapter 11), and agitation in dementia (Chapter 12). Several other disorders in which impulsivity and/or compulsivity are core features are discussed in this chapter. Full clinical descriptions and formal criteria for how to diagnose the numerous known diagnostic entities discussed here should be obtained by consulting standard diagnostic and reference sources. Here we emphasize what is known or hypothesized about the brain circuits and neurotransmitters mediating impulsivity and compulsivity, and how engaging neurotransmitters at various nodes in impulsivity/compulsivity networks can result in successful psychopharmacological treatments.
Impulsivity can be defined as a predisposition towards rapid, unplanned reactions to internal or external stimuli, with diminished regard for the negative consequences of these reactions. In contrast, compulsivity is defined as the performance of repetitive and dysfunctionally impairing behavior that has no adaptive function. Compulsive behavior is performed in a habitual or stereotypical fashion, either according to rigid rules or as a means of avoiding perceived negative consequences. These two symptom constructs can perhaps be best differentiated by how they both fail to control responses: impulsivity as the inability to stop initiating actions, and compulsivity as the inability to terminate ongoing actions. These constructs have thus been viewed historically as diametrically opposed, with impulsivity being associated with risk seeking and compulsivity with harm avoidance. Currently the emphasis is on the fact that both share different forms of cognitive inflexibility leading to a profound feeling of lack of control.
More precisely, impulsivity is action without forethought; the lack of reflection on the consequences of one’s behavior; the inability to postpone reward with preference for immediate reward over more beneficial but delayed reward; a failure of motor inhibition, often choosing risky behavior; or (less scientifically) lacking the will power not to give in to temptations and provocative stimuli from the environment. On the other hand, compulsivity is action inappropriate to the situation but which nevertheless persists, and which often results in undesirable consequences. In fact, compulsions are characterized by the curious inability to adapt behavior after negative feedback.
Habits are a type of compulsion, and can be seen as responses triggered by environmental stimuli, regardless of the current desirability of the consequences of that response. Whereas goal-directed behavior is mediated by knowledge of and desire for its consequences, habits are controlled by external stimuli through stimulus–response associations that are stamped into brain circuits through behavioral repetition and formed after considerable training, can be automatically triggered by stimuli, and are defined by their insensitivity to their outcomes. Given that goal-directed actions are relatively cognitively demanding, for daily routines, it can be adaptive to rely on habits that can be performed with minimal conscious awareness. However, habits can also represent severely maladaptive perseveration of behaviors as components of various impulsive–compulsive disorders (see Table 13-1).
|Binge eating disorder|
|Internet gaming disorder|
|Obsessive–compulsive related disorders|
|Body dysmorphic disorder|
|Impulse control disorders|
|Agitation in Alzheimer disease|
|Motor and behavioral impulsivity in ADHD|
|Provocative behaviors in mania|
|Disruptive mood dysregulation disorder|
|Autism spectrum disorders|
|Tourette syndrome and tic disorders|
|Stereotyped movement disorders|
|Borderline personality disorder|
|Self harm and parasuicidal behaviors|
|Antisocial personality disorder|
|Oppositional defiant disorder|
|Intermittent explosive disorder|
|Aggression and violence:|
Another way to look at addiction is as a habit much like the behavior of a Pavlovian dog! That is, drug seeking and drug taking behaviors can be viewed as conditioned responses to the conditioned stimuli of being around people or places or items associated with drugs, or having craving and withdrawal. When addicted, drug seeking and taking are automatic, thoughtless, conditioned responses that occur in an almost reflexive fashion to conditioned stimuli, just as Pavlov’s dogs developed mouth-watering in response to a bell associated with food. When such stimulus–response conditioning runs amok in addiction, it does not perform an adaptive purpose of sparing cognitive efforts from doing routine tasks. Instead, the “habit” of drug addiction has become a perverse form of learning, almost as though one has learned how to have a psychiatric disorder!