Fear and Anxiety: A Two-System Framework

Using Neuroscience to Help Understand Fear and Anxiety: A Two-System Framework. – PubMed – NCBI – Am J Psychiatry. Nov 2016

This makes sense to me because my anxiety isn’t specific like fear is. When I’m anxious, whatever I’m thinking about makes my stomach clench with dread, but when I’m afraid, I fear a specific situation.

Tremendous progress has been made in basic neuroscience in recent decades. One area that has been especially successful is research on how the brain detects and responds to threats.

Such studies have demonstrated comparable patterns of brain-behavior relationships underlying threat processing across a range of mammalian species, including humans.

This would seem to be an ideal body of information for advancing our understanding of disorders in which altered threat processing is a key factor, namely, fear and anxiety disorders.

But research on threat processing has not led to significant improvements in clinical practice.

The authors propose that in order to take advantage of this progress for clinical gain, a conceptual reframing is needed.

Key to this conceptual change is recognition of a distinction between circuits underlying two classes of responses elicited by threats:

1) behavioral responses and accompanying physiological changes in the brain and body and

2) conscious feeling states reflected in self-reports of fear and anxiety.

This distinction leads to a “two systems” view of fear and anxiety.

The authors argue that failure to recognize and consistently emphasize this distinction has impeded progress in understanding fear and anxiety disorders and hindered attempts to develop more effective pharmaceutical and psychological treatments. The two-system view suggests a new way forward.

Circuitry for Fearful Feelings, Behavior Untangled in Anxiety Disorders PubMed – NCBI – Sep 2016 • Science Update

An “incorrect” assumption that fear and anxiety are mediated in the brain by a single “fear circuit” has stalled progress in developing better treatments for anxiety disorders, argue two leading experts. Designing future research based on a “two-system” framework holds promise for improving treatment outcomes, say Daniel Pine, M.D.

Neuroscience advances in understanding how the brain detects and responds to threat have failed to translate into significantly improved treatments because the field has been led astray by a simplistic notion of a “fear system,” contend Pine and LeDoux.

For example, hopes that medications that lessen rodents’ stress reactivity might help people feel less fearful or anxious often haven’t borne out.

It seems absurd to try modeling disorders that stem from human brain function, like anxiety, depression, or addiction, in rodents. Chronic pain cannot be modeled in animals if it really is a biopsychosocial disorder as many claim.

They can’t say “psychological and sociological factors greatly influence pain perception” and then cite pain studies that were done on animals.

Rather, the authors point to mounting evidence that such subjective feeling states are mediated via different circuitry than defensive behaviors. The former via higher order processing in the cortex – and the latter via the amygdala and related centers, mostly deeper in the brain.

Fear and anxiety describe conscious subjective feeling states; defensive reactions refer to rapidly-deployed behaviors or physiological responses.

Fear denotes feelings associated with an imminent threat, anxiety feelings associated with an uncertain or more distant source of harm.

For example, the amygdala, often colloquially dubbed the brain’s “fear center,” in fact unconsciously detects and responds to imminent threats and contributes to fear only indirectly.

States like fear and anxiety instead arise from areas of the cortex associated with higher order thinking processes and language in people, only some of which occur in other animals.

It’s hard to imagine a rat with anxiety about how they’re going to pay for retirement, or how they’re going to find affordable housing. Yet these are precisely the kinds of thoughts that can trigger my anxiety.

If feelings of fear or anxiety are not products of circuits that control defensive behavior, studies of defensive behavior in animals will be of limited value in finding medications that can relieve feelings of fear and anxiety in people,” observe the authors, who note that making such distinctions will help in the design of more realistic translational studies.

the experience of fear and anxiety is rooted in cortical changes in thinking, attention and memory, some “anxiolytic” effects might result from “general emotional blunting” or “impaired cognitive processing,” they add.

Improving treatments will require a more exact understanding of how treatments work. With this knowledge and the two-systems perspective, existing treatments might be adapted to work better. Brain imaging biomarkers might help tailor treatments to target circuit dysfunctions of specific patients.

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