Closing the Brain–Heart Loop: Towards More Holistic Models of Addiction and Addiction Recovery
Key findings
- The cardiovascular system and other sensory and visceral systems are important contributors to the neurologic processes underlying addiction
- This paper describes the overlap between one current model of addiction circuitry and the neural network that regulates cardiovascular system activity and receives feedback from peripheral cardiovascular processes through the baroreflex loop
- Improving central control of cardiovascular processes may provide physiologic "scaffolding" to support behaviorally focused addiction interventions
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The cardiovascular system and other sensory and visceral systems are important contributors to the neurologic processes underlying addiction. They provide contextual information to the brain, often outside of conscious awareness.
Clinical Psychologist David Eddie, PhD, of the Recovery Research Institute and Center for Addiction Medicine at Massachusetts General Hospital, and colleagues believe neurobiological theories of addiction must consider brain–body information streams, not just the interplay between different regions of the brain. In an invited review in Addiction Biology, they focus on one such information stream—the cardiovascular processes regulated by the constellation of connected brain structures known as the central autonomic network (CAN).
Using the example of Koob and Volkow's three-stage model of addiction—binge/intoxication, withdrawal/negative affect and preoccupation/anticipation/craving—the authors illustrate overlaps between addiction processes and the primary functions of the CAN.
Intoxication Alters Cardiovascular Control
A number of subcortical structures are thought to drive the acutely reinforcing properties of alcohol and other drugs. These structures, many of which are shared by the CAN, are highly interconnected with brainstem areas that regulate the cardiovascular and respiratory systems.
Alterations of cardiovascular processes during acute intoxication have been extensively documented, including:
- Decreased heart rate variability, a marker of cardiovascular adaptive capacity
- Decreased blood pressure variability
- Decreased sensitivity of the baroreflex, the neurally mediated feedback loop that modulates blood pressure
Loss of flexibility in the cardiovascular system might mean that less accurate information about physiological context is relayed to the brain, contributing to the aberrant cognitive, affective and behavioral features of addiction.
Cardiovascular Features and Withdrawal/Negative Affect
The neural structures of the CAN merge feedback from the heart and vasculature with cognitive and affective factors derived in the brain. In the process, visceral constituents of withdrawal become embedded in the individual's subjective experience. Tachycardia and diaphoresis, for example, are inextricably linked to the negative affective experience of acute withdrawal.
Cardiovascular Information Is Integrated Cortically
The baroreflex feedback loop delivers cardiovascular information to and from the brain via baroreceptors—mechanoreceptors in arterial walls that respond to vessel stretching in response to moment-to-moment changes in blood pressure. Baroreceptors convey information to neural centers that control behavioral responses as well as vasculature tone and heart rate.
Experimental evidence suggests baroreflex-mediated signaling influences substance use behavior through visceral arousal responses elicited by cues in the environment. For example, the sight of a regularly attended drinking establishment can influence attention and perpetuate or exacerbate preoccupation, anticipation and craving.
Clinical Implications
Improving central control of cardiovascular processes may provide physiological "scaffolding" to support behaviorally focused addiction interventions. Examples include:
- Biofeedback about heart rate is able to affect major shifts in autonomic activation, so it may be able to enhance CAN regulatory capacity to buffer against craving
- The alpha-blockers prazosin and doxazosin have been shown to reduce stress reactivity, craving and the use of alcohol and other drugs in people with a substance use disorder
- Acamprosate, a centrally acting GABA agonist and glutamate antagonist, is hypothesized to reduce hyper-glutamatergic states associated with craving
Treatment adjuncts that target cardiovascular regulatory mechanisms may also accelerate cardiovascular recovery from addiction, sustain substance use behavior change and improve general health and quality of life.
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